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Foreword, Preface, About Author

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Chief Vincent Dunn declares firefighting is a war and the buildings are the Firefighter’s battlespace. A battlespace is the total fire environment; the inside and outside of a burning building. A battlespace is not just a room and fire; it includes much more. It is the doors and windows, stair enclosure we use to get to the fire, outside walls of a building, inside room configurations, rooftop hazards, structure framing, metal fire escapes, ceiling spaces, voids behind walls, floors, roof construction and more. The term battlespace is not the same as battleground or fireground. It is the total firefighting environment that must be understood to successfully combat fire, protect Firefighters and complete the mission of saving lives and property.

Chief Dunn also introduces another concept in this book, called “a Game-Changer.” Game-changers are identified at the end of every chapter. A game-changer is notification of an event, construction feature or fire growth that changes an Incident Commander’s (IC) thinking or strategy. When a game-changer occurs, it can begin or bring about an immediate change in an IC’s thinking at the fire, alter his/her strategy, end an operation or, in extreme instances, prompt the withdrawal of Firefighters.

Some examples of firefighting game-changers include:

  • Dwelling–combustible siding fire, attic fire, truss construction
  • Strip store–a common roof space fire, backdraft signs, unstable parapet
  • Triple-decker–a siding fire, cockloft fire
  • Multiple dwelling–a shaft fire, wind-driven fire, cockloft fire
  • Warehouse/loft–cast-iron columns, heavy storage, prolonged fire on two floors, cellar fire
  • Place of worship–fire in an attic, bell tower, steeple or when smoke obscures ceiling
  • Lightweight construction building–reports of truss or wood I-beams and fire in these structure elements
  • High-rise buildings–floor distortion, wind-driven fire, exterior finish laminated surfaces
  • Fire escape--a broken step, people descending the ladders or steps
  • Steel and glass buildings–PVC, PCB smoke and uncontrolled fire for more than two hours
  • Construction demolition site--broken standpipe, asbestos removal
  • Floor crumbling–terrazzo tile
  • Rooftop attic fire—trusses, wood I-beams
  • Timber truss mounded roof–large space, no columns, occupancies such as supermarkets, theaters, garages, auto dealerships, places of worship, bowling alleys, piers, armories, lumberyards
  • Walls that are leaning, parapets or attached to collapsing floors
  • Ceilings suspended one below another
  • Topography in a building that is vacant, under construction, demolition or renovation
  • Structure framing in buildings built before code or outside zoning limits
  • Stairs blocked by people, fire or collapse
  • Type I, fire-resistive fire beyond hose-line extinguishment, controlled burning interior operations more than two hours long, wind-driven, exterior insulation finish fire or terrorism-related
  • Type II noncombustible/limited combustible, open bar joists truss
  • Type III ordinary cockloft fire, unstable floors or walls
  • Type IV heavy timber fire overwhelming hose streams, cast-iron columns, cross-laminated timbers
  • Type V balloon construction, concealed space fire, cockloft attic fire, siding fire, wood trusses, wood I-beams
  • Recurring fire and collapse patterns, good fireground communications, reports to Command by Firefighters and Fire Officers.

This book is written only for Firefighters, Fire Officers and Chief Officers who respond to structure fires.


I say our war with fire is fought room to room and house to house. Buildings are our battlespace. Firefighters must understand our work is war and our work environment is a battlespace; full of flame, explosion, flashover, backdraft blasts, heat, smoke, toxic gases and structural collapse. The battle first starts when we enter a burning building; climb stairs engulfed by smoke and heat; crawl down a hallway with overhead scalding water and hot plaster and sparks raining down from ceilings; scrambling over red, hot ashes, burning knees; ceiling chunks crashing down on helmets; television tubes exploding in ears; all while struggling to direct a high-pressure hose stream shooting a ton of water at flame. It is in this kind of battlespace we are killed and injured by combustion products, flame, heat, smoke and toxic gases.

After we recognize that our work environment is hellish and we call it what it is--a battlespace—we next must learn as much as possible about the battlespace--building construction. The battlespaces of the most common types of construction and types of occupancies are examined in this book. A battlespace can be a stairway, hallway, attic hallway, room, apartment, private dwelling, strip store, triple-decker, multiple dwelling, loft building, place of worship, lightweight truss building, skyscraper high-rise building, fire escape, glass and steel building, building under construction, floor, roof, timber trusses, wall, ceiling, topography, structure framing, fire-resistive construction, noncombustible/limited combustible construction, ordinary construction, heavy timber construction and wood-frame construction.

About the Author:

Vincent Dunn served with the New York City Fire Department for 42 years and rose up through the ranks of the Department: seven years as a Firefighter, nine years as a company Officer and 26 years as a Chief Officer.

Graduated top of his class, Officer Candidate School 1964, FDNY Division of Training. Responded to the 23rd Street Wonder Drugstore fire where 12 Firefighters died in a floor collapse. Based on that fire, he wrote Collapse of Burning Buildings, a guide to fireground safety, used by fire departments around the nation.

Authored four other books: Safety and Survival on the Fireground, second edition, 2014; Collapse of Burning Buildings, second edition, 2010; Strategy of Firefighting, 2006; Command and Control of Fires and Emergencies, 1999.

Advisor to the National Institute of Standards and Technology on the World Trade Center Towers Collapse 9/11.

Attending college at night with the assistance of the G.I. Bill, he received AAS, BA and MA degrees from Queens College, City University of New York.

An adjunct professor of Manhattan College, he taught Fire Engineering Design in the civil engineering department and as an adjunct professor of City University of New York, John Jay College, he taught Strategy of Fire and Emergencies.

He was a regular contributor to FDNY’s official training publication—WNYF (With New York Firefighters)—and is a contributing Editor to Firehouse magazine and the B-shifter electronic magazine, writing articles on building construction and collapse.


  • 2017 Man of the Year, Friends of Firefighters
  • 2015 Hall of Fame, Firehouse magazine
  • 2012 Lifetime Achievement Award, FDNY Honor Legion Society
  • 2000 Lifetime Achievement Award, New York City Fire Department
  • 1999 Lifetime Achievement Award, Fire Engineering
  • 1 995 New York City Fire Safety Directors Association Edward W. Whalen Award
  • 1991 Man of the Year, Society of Fire Protection Engineers

Chief Dunn can be reached at Also, visit his website at

New Material In This Book:

  • A timber truss trilogy tragedy
  • Building systems--how to use them and how they fail
  • Ceiling construction hazards above and below
  • Collapse danger ranking of a place of worship facade
  • Construction types ranked according to fire risk
  • Cross-laminated timber construction (CLT)
  • Deadly communication misunderstandings in the battlespace
  • Exterior insulation finish system (EIFS) and cladding fires
  • Exterior wall size-up
  • Fire escape corrosion hazards
  • Game-changers
  • Glass and steel construction
  • High-rise construction fire spread and collapse dangers
  • Lightweight wood truss conflagration hazards
  • Private dwelling interior design dangers
  • Size-up stairway construction
  • Stairway firefighting tactics
  • Strip store construction defects and hazards
  • The 25 ways fire spreads in building structures
  • The fire spread weakness of each type of building construction
  • The heavy timber cross-laminated timber construction myth
  • The new target hazards--places of worship
  • Topography and floor layouts of building occupancies
  • Triple-decker construction fire and collapse dangers
  • Underwriters Laboratories and NIST floor testing

First, I would like to give great thanks to Editor Janet Kimmerly. She is the force behind this book and all my writing, all the time.

I also would like to give special thanks to some great photographer friends: Dan Hamelburg and Steve Spak, for the front and back covers, respectively; and Ron Jeffers, Matt Daly, Warren Fuchs, Harvey Eisner (deceased), Pat Dunn, Joe Hoffman, Jim Smith, Chuck Wehrli, Mike Terpak, Pat Grace, Nicholas Papa, Julie Manso, Don Van Holt, Richard Kubler and Joe Berry.

Book cover design: Faith Deutsch

Most of all, I must thank my expert Editor friends

Janelle Foskett and Michelle Garrido Sutton, the secrets to my writing.

Chapter 2: Strip Store Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A strip store is a complex, dangerous battlespace because of the combustible content and structure layout. A lack of windows on its side walls creates a space designed for explosions and flashover to blow in the path of advancing Firefighters. Entering a burning store can be similar to advancing into the barrel of a loaded shotgun that can go off at any time. On the outside, a strip store battlespace is heavily fortified behind locks, metal shutters, gates and bars. On the inside, its interior layout may contain highly combustible material on shelves and storage tables and behind counters. Above advancing Firefighters there may be multiple suspended ceilings concealing flame overhead. And, above the suspended ceiling is a large, common roof space that may be open to the adjoining building roof spaces.

Preventing fire from spreading in the common roof space of a strip store is one of the major challenges to an Incident Commander (IC). Another challenge is the collapse danger of a parapet wall on the outside, above the glass show windows. In the northeast, a strip store is called a “taxpayer,” a name coined by builders to define a cheaply constructed, temporary, one-story structure that can be rented for enough money to pay taxes on the property until it can be torn down and replaced with a better built, permanent structure. This cheaply constructed structure is a collapse danger. Today, upscale shopping centers have incorporated the same design layout of the old taxpayer strip store. The following is a list of strip store battlespace features that can help a Fire Officer safely and effectively fight a fire.

chapter image Fig. 2.1  Strip store fires are difficult to extinguish and dangerous to fight.

Parapet wall

A parapet is a deadly wall that has killed many Firefighters. A parapet wall is that part of a wall that extends above roof level. It is a decorative, freestanding wall at the front of a strip store that can extend one to five feet high above the roof level. The front parapet usually is higher than the other parapets in order to give the building a more imposing look and sometimes it has an ornamental stone or brick overhang cornice at the top that makes it more unstable. If brickwork is used as an ornamental cornice on the top portion of a brick front parapet wall, it is called corbelling. Corbel brick or stone projects out from the surface of the wall like a cantilever. Parapet walls with corbelled brick tops or cast stone overhangs are unstable walls that can become a collapse danger.

Parapet walls on buildings in earthquake-prone areas of the country are limited in height. Western local building codes limit the height of front parapet walls to 18 inches in height because of their history of failure during tremors and shocks of earthquakes. Explosions during fires have the same effect as earthquakes. Firefighters operating hose-lines, raising ladders or operating in buckets of tower ladders that are inside a collapse zone near a parapet have been buried under falling bricks of parapet wall collapse. A Fire Officer size-up arriving at a strip store fire must include an evaluation of the parapet. Because it may be difficult to see a parapet due to advertising, darkness or smoke at a fire, it is better to evaluate all parapets during building inspections before a fire. Check them out when responding or returning from alarms.


Lintel beam

The steel beam that supports a parapet wall on a storefront wall that has large, glass show windows is called a lintel. And a masonry parapet wall on top, which is supported by a steel I-beam spanning the window, is called a lintel beam. During a major-alarm fire when front show windows have vented flames out of the store, heat can distort this steel lintel beam. If the steel beam warps, bends, twists or buckles, it could trigger collapse of the masonry parapet wall supported above. During a fire, the IC should keep an eye on the steel I-beam lintel for distortion that could lead to collapse. When there is danger of a parapet wall collapse, Fire Officers should withdraw Firefighters from the collapse danger zone. The distance Firefighters should be withdrawn should be one, one and one-half or twice the height of the store parapet wall, as directed by the IC. The exact distance depends on the possibility of the wall being pushed out further than the height of the wall by pressure of sloping roof rafters of a truss or mansard roof or the possibility of an explosion.

Coping stones

On top of a parapet wall at the front of a strip store are coping or capstones to prevent rainwater from entering the cement that binds the bricks. These are similar to heavy cinder blocks resting on top of the parapet. Coping stones can come loose if the mortar loses its adhesive qualities. Ladders scraping against them when being lowered or powerful hose streams can knock these five- or 10-pound coping stones off a parapet wall, crashing them down on top of Firefighters operating in streets and alleys around a strip store. When directing master steams and positioning and removing aerial ladders from a store roof, Officers should avoid striking a coping stone.

Truss construction

Strip stores can have lightweight, truss wood beams or steel bar joists truss supporting roofs and floors. A Fire Officer must know if these truss structures support the roof because these members can fail within five to 10 minutes when unprotected and exposed to fire. At a strip store, Firefighters immediately must report the presence of any type of truss to the IC. This hazard identification and reporting are keys to safe firefighting at a burning building with truss construction. An IC cannot order a safety action unless notified of the danger. This information is critically important for incident command decision-making. Firefighters should not operate on a store roof supported by truss construction during a fire that involves the truss structure.

Cantilever loads

Strip stores are “make believe buildings” that use architectural decorations on front walls to make the structure look more imposing. These decorations include marquees, canopies, cornices and high decorative parapets. All of these decorations are unstable cantilever structures protruding from the exterior walls. A cantilever is a beam supported at one end, unlike a simple beam that is supported at both ends. These decorative cantilever add-ons to parapet walls of a strip store should be noted at fires because they can collapse and pull down parts of a wall with it.

Firefighters call a marquee a swimming pool hanging off the wall of a store. A canopy usually is found at the rear of a store and protects workers from the elements when they unload merchandise from trucks.

Canopies protect from the elements, but are not designed to support roof weight. Firefighters climbing up on a canopy with hose-lines can collapse the structure.


There is no purpose to a storefront decorative cornice other than decoration. A cornice sign also can spread fire from one story to another. A Fire Officer must check behind a cornice attached to a parapet by wood furring for fire spread. A wood cornice called an “eyebrow,” located at the top of a storefront, can spread inside its wooden interior framework and suddenly collapse like a wave. A wood cornice also can collapse if struck by the impact of a ground ladder placed against the building or from the powerful water stream of a tower ladder striking it.

And, it must be remembered, a parapet wall actually is a vertical cantilever supported at the bottom only. If it has a cantilever cornice, canopy or marquee cantilever attached, it is more deadly.

Fire divisions

Stores in a row sometimes are divided by masonry party walls. This is not a fire division. There are no fire divisions in a strip store row. The walls dividing stores actually are party walls with roof beams from both stores supported by one wall. A party wall differs from a fire division. Fire Officers must understand this difference. An official fire division is an independent, solid wall structure, with a documented three- or four-hour fire-resistive rating that has its own foundation and no wood beam penetrating it. A party wall parapet that extends above the roof of a strip store may look like a fire division, but it is not. A strip store brick party wall has roof and floor beams from two adjoining stores penetrating it, which creates small spaces through which flame and smoke can flow. A party wall protruding above a roof may look good, but if you go below, into one of the stores and pull ceilings, you will see missing bricks and mortar, openings for old air conditioning ducts, poke-through holes for electric wires and plumbing fixtures. We say don’t trust a truss for roof and floor stability and I say don’t trust a party wall to stop fire. Before you make a hose-line stand on a roof behind a party wall, the IC must have Firefighters go into the store, pull a ceiling and examine a party wall from below.

chapter image Fig. 2.2  Because it may be difficult to see a parapet due to advertising, darkness or smoke at a fire, it is better to evaluate all parapets during building inspections before a fire. Check them out when responding or returning from alarms.

Store glass

There are three important glass openings in a strip store. You have large, glass show windows in the front, a door or small window at the rear and sometimes glass skylights on the roof. A Fire Officer must know how and when to vent these glass portals to safely release smoke without causing a flashover or backdraft explosion. In a row of stores, there are no side windows for venting. You can vent only the top, front and rear of the store windows. Venting glass at a store fire is very important because of the danger of backdraft explosions. If there are signs of backdraft explosion after venting, Firefighters with hose-lines should flank the fire opening and if a blast occurs, they will be on the side of it. Firefighters advancing a hose-line into a store are entering the barrel of a loaded shotgun and improper venting can pull the trigger. Any explosion blast in a strip store will be driven right back into Firefighters.

As a general rule, venting at a store fire is done first at the roof level. Skylight venting will slow down flame seeping through a store ceiling into the cockloft. And if there is an explosion in the store, the roof skylight vent can divert a blast upward. The next opening vented should be the rear window or door to allow smoke and heat pushed ahead of advancing Firefighters out the rear of the store. Finally, the front windows have to be taken out as the hose team enters the store. This procedure is for explanation; firefighting cannot be controlled this closely.

Recently, the National Institute of Standards and Technology (NIST) conducted ventilation studies at fires. The NIST vent guidelines state no venting should be carried out before the hose-line is ready to advance. If you must force entry to a store after forcing a store door, temporarily close it until the hose-line is ready. When the hoseline advances, all three glass openings then can be vented simultaneously. This coordinated venting will reduce the danger of flashover and backdraft explosion. But in real life, this coordinated venting cannot be realistically accomplished.

A Fire Officer should know

  1. The roof skylight venting at the top can release heat and smoke from the store even if the front and rear glass is intact.
  2. When the hose-line and Firefighters are ready to advance into the store to extinguish the fire, open up the front door and nearby show windows.
  3. Firefighters should be ordered to vent the rear window and doors simultaneously with the advance of the hose-line.

The best we can do is not vent the front door or window until the hose team is ready to advance. All glass venting at a store fire--front, top, and rear--should be coordinated with the advance of the hose-line. It is a fact that premature front door and window glass venting can trigger a flashover or backdraft/smoke explosion if it is done and the hose team is not ready.

The only time window venting in a store should be done prior to the hose-line advance is if a trapped person inside is seen, heard calling for help or a credible witness states a person is trapped inside and a rescue can be attempted. When a Firefighter decides to make this life and death decision to vent, he or she then must enter the smoke-filled area, search and remove the trapped person.


Many rookie Firefighters mistakenly think skylight venting of a store removes smoke and heat from the common roof space. This is not true. To vent a common roof space, you must cut the roof with a saw. Venting a skylight does not vent the cockloft.

chapter image Fig. 2.3  The load of roof machinery must not rest directly on roof beams, but instead be independently supported on steel I-beams that transmit the load to bearing walls.

Common roof area

A common roof space, sometimes called a cockloft, is a space above a ceiling and below a roof that extends over several stores in the row. It is a major construction defect found in many strip store buildings. After life concerns and fire extinguishment, a Fire Officer’s goal at a store fire is to keep the fire from entering this common roof space. If fire burns through a ceiling and gets into the common roof space, it can spread and involve all the stores in the row; sometimes the entire block. In some store construction, a brick fire partition separates the common roof area at each store, but a Fire Officer never must assume that there is a fire partition. During the early stages of a store fire, a Fire Officer must order Firefighters to open up a section of ceiling in the adjoining stores and check to see if fire has entered the common roof space and is spreading there.


The IC’s hose-line strategy must be designed to prevent fire spread in the common roof area of a strip store. For example, after the first line is advancing on a fire in the store of fire origin, the next hose-line should be stretched into the adjoining downwind store and the ceiling opened and fire cut off with the hose stream here. Firefighters in this downwind store must check the partition separating the fire store and determine possibility of fire spread. If there is no fire extension to the downwind store, this information is relayed to the IC. The IC orders a third hose-line stretched into the upwind store, the ceiling is opened up here and fire extension evaluated. Every effort at a strip store fire by every Officer is to prevent fire from entering the common roof area and if it does spread here, every effort is made to prevent it from spreading over the other stores.

Suspended ceilings

Over the years, as businesses change, the occupancy is renovated and this usually includes a new ceiling. Sometimes, business owners do not remove the old ceiling and just put up a new ceiling below the old one. To do this, holes are put in the original ceiling. If fire burns through the lowest ceiling, it will spread through the ceiling above into the common roof space. It is very difficult to open up several ceilings and extinguish the fire in the common roof space.

When opening a ceiling to check for fire, an Officer must open up all ceilings, not just the lowest one, to give the hose stream access to the common roof space. If you open up a ceiling to check for fire spread and see another ceiling above it, this ceiling also must be opened with hooks.

When multiple ceilings are discovered, the IC must be notified. If all suspended ceilings are not opened, a roof space fire will not be extinguished by a hose stream. When there are poke-through holes in several ceilings, fire will spread quickly up through them into the common roof space.

Another reason to check the spaces above a suspended ceiling is that suspended ceilings are a major collapse danger during a store fire. If fire enters the common roof space and destroys the hanger framework supporting the ceiling, the entire frame system can collapse like a net over Firefighters in the store.

Roof machinery

The most common roof machinery found on the roof of a store is the air conditioner unit. When discovering roof machinery on the roof of a store during a fire, the Officer must determine if it is independently supported by steel beams or resting on the roof deck. If supported by steel I-beams, the beams should span the roof and be supported at each end by a bearing wall. The load of the HVAC system must not rest on the roof beams, but instead be transmitted horizontally to bearing walls, then vertically down to the ground through the bearing walls. It is important that this steel beam support relieve the roof beams of any additional weight. The independent steel beam supports are designed to allow the roof to be damaged by a store fire below and not cause a collapse. On many of the new fast food restaurants, the heavy HVAC roof machines rest directly on the roof, adding weight to the roof structure and posing a collapse danger. During a fire when the roof beams burn, the HVAC roof machine can collapse through the roof on top of the Firefighters operating in the store. Any HVAC or other machine discovered on the roof of a store during a firefight should be reported to the IC. However, it is most important to determine whether the roof machines are independently supported or resting on and supported by the roof. This is collapse information that must be included in the roof size-up.

chapter image Fig. 2.4  After life concerns and fire extinguishment, a Fire Officer’s goal at a store fire is to keep the fire from entering this common roof space (cockloft).

Scuttle covers

A Fire Officer should note the presence of scuttle covers in a roof size-up. Some store roofs have square or rectangular scuttle covers. They provide access openings to a roof from the store below. Firefighters should be careful not to step on them; the scuttle covers could collapse and the Firefighters fall through to the burning store below. Scuttle covers are not designed to support the weight of a Firefighter. Unlike the rest of the roof, there are no roof rafters below them. Treat them as you would a skylight. In fact, some scuttle covers actually are old skylights that were covered with plywood and tar paper, instead of repairing the glass when leaking or broke. The store owner may reason that since the original skylight was not designed to support the weight of a person walking on the roof, the replacement cover does not need reinforcement. Fire Officers should caution Firefighters operating on a roof scuttle that covers are collapse hazards.


In a row of stores, the only access to a cellar that holds stock or storage may be though a trapdoor in a floor. A trapdoor is a hidden opening in the floor of a store. The door has a recessed handle that is used to pull up a section of flooring that opens up to a ladder or stair leading to a cellar. These trapdoors must be closed at night or they become a hazard. Unfortunately, trapdoors are left open and Firefighters searching in smoke can fall into the cellar. Trapdoors are found behind a counter or in an aisle of a store where Firefighters search.


At a store, Fire Officers always must be alert to the danger of a trapdoor during smoky fires. The location of store trapdoors should be documented during fire prevention or fire pre-plan inspections. To avoid falling through an open trapdoor when searching in smoke, Firefighters should use a tool to probe a floor and, when advancing a hose in smoke, keep one leg outstretched to feel for a sudden floor opening and support body weight on a back leg. A wooden trapdoor usually is made of the same material as the floor boards and it is difficult to identify. There will be no beam support for the trapdoor floor, so this floor section will be the first area to weaken during a cellar fire below. A trapdoor creates a concealed, three- by six-foot section of unsupported floor deck that can collapse, taking any Firefighters standing on it down into the cellar.

Metal sidewalk cellar doors

In front of a store there can be another opening to the cellar. This easily identified sidewalk cellar entrance stair in front of a store is used by truck vendors to load stock in a cellar without entering the store. This service cellar entrance is a pair of steel trapdoors, flush with the sidewalk directly next to the storefront window. The metal sidewalk cellar entrance door leads to a steep concrete or open wooden stair. This cellar entrance has no fire-retarding enclosure at the bottom of the stairs. Any flame and heat in the cellar will flow straight up and out of the sidewalk opening. If the cellar fire is severe, there is a strong likelihood the wooden stairs leading to the cellar have burned away or been weakened by fire. Sudden collapse of a cellar step could cause a Firefighter descending the cellars steps, directing a hose stream, to lose his/her balance and tumble into a burning cellar.

chapter image Fig. 2.5  Sudden collapse of a cellar step could cause a Firefighter descending the cellar steps, directing a hose stream, to lose balance and tumble into a burning cellar.

Truck delivery persons sometimes place a chute or roller device over the stairs, designed to slide packages and boxes down to the cellar and these chutes or carton rollers are left in place over the steps. During a smoky cellar fire, these chutes and rollers may be obscured. Firefighters attempting to descend the smoke-filled sidewalk cellar stairway may slide into the burning cellar. Even if the chute is seen, it can block the cellar steps, preventing a hose-line advance unless removed. Escape from a fire in a cellar whose stairs are covered with a package chute or roller slide is unlikely.

A strip store fire battle plan

  1. The firefighting strategy in a strip store battlespace is cutting off fire before it reaches the common roof space (cockloft). If it does spread there, cut it off before it reaches adjoining stores.
  2. The first attack hose-line is stretched to the store of fire origin to extinguish a content fire before it burns through the ceiling to the common roof space. A first attack hose-line usually immediately extinguishes 95 percent of all fires. As soon as the fire is knocked down, ceilings are pulled to determine if the fire has spread to the common roof space. The common roof space may extend over all the stores in the row of the shopping center or mall. If fire enters this concealed space, flames may spread through the common roof space and destroy the entire complex of strip stores.
  3. The second hose-line is stretched to the store on the downwind side of the fire store to cut off fire spreading in the common roof space. The downwind store in a row of stores is a usually serious exposure danger. The Officer in charge of the second hose-line in the downwind store should have Firefighters with pike poles pull down the ceiling along the partition wall separating the exposure store from the store of fire origin. A hose-line should be used to stop fire spreading to the downwind exposure. As soon as possible, notify the Officer in command of the fire conditions and the ability of the hose stream to contain the fire or if the fire will spread beyond the downwind store. This information will enhance the strategy.
  4. A third line should be stretched into the upwind store as soon as resources are available. Even if there is no indication of fire, this hose should be stretched here, the ceiling pulled and the common roof space examined. The second hoseline in the downwind store is to stop fire spread. The third line in the upwind store will confine or contain the fire. Notify the IC whether the fire is spreading or contained. 
  5. A portable ladder should be raised to the roof upwind from the fire store, away from the fire and smoke. The placement of the ladder upwind to the fire will ensure the smoke and flame from spreading fire or smoke will not obscure or cut off escape of Firefighters on the roof. The extension ladder tip should be raised several feet above the parapet wall so it will be visible to Firefighters on the roof.
  6. The primary venting at a strip store fire is the skylights and scuttle covers that serve the store of fire origin. Firefighters on the roof should vent all skylights and scuttle covers that serve the burning store. This venting will delay flame from penetrating the ceiling and entering the cockloft and reduce the effects if there is a flashover or backdraft explosion in the fire store. Any blast will go up, not horizontally into the faces of advancing Firefighters. The front and rear window glass and doors are vented when the hose-line is ready to advance. This horizontal venting is coordinated with hose advancement. At the first sign of fire in the cockloft, the roof deck should be cut. A vent opening should be cut in the roof to vent flame and heat out of the common roof space before it starts to spread horizontally over the adjoining stores.
  7. An aerial ladder should be positioned downwind from the fire or where it could be used to protect high exposures if the interior attack fails. If needed, another aerial ladder for master stream use should be positioned on the upwind side. If the entire store becomes involved in fire, four aerial master streams may be required on each exposure side.

The game-changer

The game-changers are fire in the common roof space, an unstable parapet wall or a backdraft explosion potential. As soon as a fire is knocked down, the ceiling should be opened and the cockloft checked for fire. A collapse danger zone may have to be set up near the parapet. Venting the front, rear and roof opening are necessary to reduce the effects of explosion or flashover. You may have to skip one or two stores in order to find the forward edge of the common roof space fire spread so all gates and locks on all stores in the row must be opened. Position a tower ladder on the downwind side of the fire store to protect exposures or for use if interior operations fail. When explosion is possible, Firefighters should flank the fire entrance.

Strip Store Battlespace Casualties

Two Boston, Massachusetts, Firefighters trapped under ceiling collapse while battling cockloft fire. NIOSH 2007-32

Chapter 3: Triple-Decker Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


The triple-decker is a treacherous battlespace where, on arrival, fire can be spreading on several fronts: the interior rooms can be burning and flame can be spreading up a shaft and on the outside up the exterior siding walls if it gets into the cockloft to the adjoining buildings. And, if the building is located at the end of a row or stands alone, it can collapse. The most common triple-decker is Type III or V construction and features a narrow wood stair, wooden apartment doors and a railroad flat layout--front to rear--and no fire escapes. If fire spreads to the cockloft and adjoining buildings through a common roof space, the entire block can burn.

Century-old triple-decker design structures have been renovated or new ones built and called condominiums or townhouses, but these structures have the same battlespace hazards as the old triple-deckers, with tremendous firefighting challenges. The following are some construction problems presented by triple-deckers: concealed spaces, interior shafts, combustible walls, wood porches, common cocklofts and collapse.

Structure framing

Because of the height and size of the wood, century-old triple-decker wood construction is braced-frame construction (post and girt). The modern triple-deckers are platform construction. To reinforce the height of the buildings, four vertical timbers called posts are situated at the four corners of the structure for stability; girts or wood timber girders are used to support each floor. Wood timbers are found at the bearing wall sides of each floor level to support floor beams. Girders are connected to posts by mortise and tenon connections.


Older post and girt triple-deckers were required to have shafts to provide light and air to bathrooms, kitchens and interior rooms of the apartment. The shafts are a major fire spread problem. The interior of open front or rear shafts spreads fire to several floors quickly. Any room fire that breaks out a window, enters a shaft and extends up combustible siding ignites the window frames or enters any open window of upper-floor apartments and even through the shaft eaves into the cockloft. It can enter a cockloft around the rotted or missing trim at the top of the shaft enclosure eaves.

After a hose-line is stretched to a room fire, as soon as the fire is knocked down, you must check for shaft fire spread. If fire has spread up the shaft, a second line must be stretched to the top floor and the ceilings pulled around the shaft top to check for fire spread into the cockloft. A third line must be stretched to protect the second hose-line team from being cut off by fire or a ladder raised to the top floor to ensure an escape route if the interior stair becomes untenable.

Modern triple-decker construction

Modern triple-decker construction does not use post and girt construction; it is platform construction. These modern triple-deckers may have fancy, decorative facades and various rooflines and are called new names, such as townhouses or condominiums, but if they are three stories, they are triple-deckers and present the same firefighting problems as the century-old structures.

chapter image Fig. 3.1  A row of triple-deckers with fire spreading in the common roof spaces.

They present a new firefighting problem the older triple-decker did not have--the lightweight truss. If the townhouse or condo uses lightweight truss construction for floors and roof in the platform construction, the building is inferior from fire spread and collapse points of view. Platform construction is a superior method of construction unless it incorporates truss floors and roof; then, it is inferior to post and girt and balloon construction.

When building with the platform construction method, the first level of the apartment walls is raised and a two- by four-inch wood plate put on top. On top of the plate, the floor beams and floor deck are placed. On top of this, the second level stud walls are raised and the process of plate, floor beams and under-flooring is repeated. And on top of this, the third floor of the triple-decker is built. Each floor is a separate section of wall; there are no studs or corner posts that extend more than one level. There are no light and air shafts.

However, in the modern triple-decker, platform construction has large and numerous vertical concealed spaces. These voids and spaces contain piping, electric and air system ducts that run up and down the structure. After a room and content fire in a platform-constructed triple-decker is extinguished, the Fire Officer must check the interior bathrooms and kitchens that have most of these concealed spaces for fire in these voids. If fire enters a concealed space of a kitchen or bathroom, it can spread quickly up to the cockloft or common roof space of the triple-decker if built in a row. These concealed spaces are not firestopped and have large poke-through holes at each floor level.

In older buildings, plaster dripping and oozing through lath walls fell to the floors and acted as firestopping. After any fire is extinguished in a modern triple-decker, any vertical concealed spaces containing utilities must be checked for fire spread up to the attic.

A Fire Officer should use the same hose stretching and ladder placement for a modern triple-decker fire. For example, when a concealed utility space is discovered spreading fire upward, the second line goes to the top floor and members check the ceiling near the shaft to see if fire spread to the cockloft or attic. A third line and/or ladder protects Firefighters on the top floor from being cut off by fire.

A modern triple-decker townhouse built with lightweight truss construction has a more deadly problem. It poses sudden, quick building collapse. A Fire Officer must know this lightweight-constructed triple-decker can collapse within five to 10 minutes after arrival. A truss floor or roof can fail much faster than a solid-beam, wood-constructed structure.

The strategy a Fire Officer should use when fire spreads throughout a floor or ceiling truss structure that cannot be immediately extinguished is to remove all occupants and fight the fire defensively. If it is only a content fire and flame has not spread through the plaster ceiling or wall and involved trusses, use a standard operating procedure. But if fire already is inside the structure and spread throughout the truss web members, notify the Incident Commander and order Firefighters to remove all occupants and fight the fire from an exterior defensive position.


Brick nogging

Fire walls between rows of old triple-deckers are built with brick nogging. Brick nogging is a term used to describe bricks placed in between wood stud walls and is found in an old, braced-frame (post and girt) constructed triple-decker.

Brick nogging used on interior wood stud walls can be seen in a cockloft between rows of triple-deckers. Its official use was for insulation, soundproofing and to provide stability and support to the structure.

Some erroneously believe its purpose is for fire-stopping. It is not. This brick infill can be found on walls between attached triple-deckers and on exterior walls where it is covered with wood clapboard or shingle siding. Brick infill is not load-bearing and because it is sometimes used to separate rows of buildings, it looks like fire-stopping. It is not. With a closer look in the common roof space of a row of triple-deckers, you can see mortar between brick nogging is missing or fallen away and, in some instances, there are openings framed into the brickwork between buildings as access openings. A Fire Officer must not consider that this will provide stability or stop fire spread in between buildings.

chapter image Fig. 3.2  A post and girt (braced-frame) triple-decker with reinforced timber columns and brick nogging.

Porches and decks

Triple-deckers have large wood porches that sometimes are considered fire escape stairs built at the front or rear of the building. However, these structures are combustible and unless continually maintained, burn and collapse. Some porches were built before a local building code was enacted and so there is no load-bearing standard for them and they have never been tested to support people during their lifetime. Wood porches may have connecting stairs for use by all floors or they could function as a deck without stairs. Either way, these structures must be considered a collapse hazard.


A typical porch, unlike the building interior, will be exposed continuously to the elements, so rot and decay occur more rapidly on the outside structure than in the interior. Cooking grills with propane, old heavy furniture and bicycles sometimes are stored on a porch and can create a fire hazard and collapse danger.

An arson fire often will be started here and quickly spread into all floors of the triple-decker. A Fire Officer must know these untested structures are fire breeders and collapse dangers and size them up before assigning several Firefighters with heavy, water-filled hose-lines to operate on them. Ladder company chauffeurs must consider the impact of an aerial ladder tip being placed on a porch railing and Fire Officers must not allow people escaping a fire to overcrowd a porch. Remove them with ladders or down porch stairs and when collapse appears likely, establish a collapse danger zone beneath and around the overhanging porch. A Pennsylvania volunteer Fire Lieutenant was killed when a porch collapsed. NIOSH Firefighter fatality report: F2002 49

Combustible siding

Some triple-deckers are masonry, but most have combustible exterior walls. Any fire inside the building also can spread out a window and start spreading up the exterior walls. A Fire Officer must know this combustible exterior does not exist on any other type construction. Exterior wall fire cannot occur in fire-resistive, noncombustible, ordinary and heavy timber buildings. They all have noncombustible exterior walls where this cannot happen. This may seem obvious, but a Fire Officer who is transferred to a district with wood exterior buildings may overlook this additional fire spread avenue.


EIFS (exterior insulation finish systems) are combustible and used on Type I and Type II construction. The firefighting strategy for a wood triple-decker fire and new structures using EIFS may require an interior attack hose-line strategy and, simultaneously, an exterior attack hose-line strategy to stop flame spreading up the side of the building. A first hose-line may have to be stretched inside and a second line or deck pipe stream used to wet down the outside.

In some older triple-decker buildings, the wood siding has been covered with an asphalt imitation brick siding. This is worse that wood exterior walls. Imitation brick is asphalt tar. It is more flammable than wood. Flames spread more quickly up the asphalt exterior walls and extend into the cockloft space through the cornice or roof eaves and, at the same time, create flaming oil droplets raining down the side of the exterior. These flaming droplets of burning asphalt can spread fire into the basement if they ignite the window frame of a window well. A simple room and content fire spreading out a window can extend up the siding into the roof space and into the cellar.

A Fire Officer must know there can be several layers of siding on a triple-decker– the original wood siding, asphalt imitation brick and aluminum siding. In a building with multiple layers of siding in between each siding layer, there will be a small space created by wood nailing strips used to attach new siding to the old. Fire can get into this small space and smolder, causing a rekindle after Firefighters leave or it can spread in this space up to the roof space or attic while Firefighters are at the scene. A Fire Officer must have Firefighters check this concealed space between layers of siding after any nearby outside fire.


The side combustible walls of a triple-decker usually are the load-bearing walls and they support the load of all the floors and roof. If one of these load-bearing side walls burns for a considerable length of time during a major fire, it will weaken and the building can collapse. If a bearing wall is weakened by fire and fails, the floors it is supporting will follow in collapse. Of the five types of building construction—fire-resistive, noncombustible, ordinary, heavy timber and wood frame--the wood-frame building is the only structure that has load-bearing walls that can be destroyed by flame.

chapter image Fig. 3.3  In some older triple-decker buildings, the wood siding has been covered with an asphalt imitation brick siding. This is worse than wood exterior walls.

Wood connections

A triple-decker post and girt construction can be identified by wood mortise and tenon connections of the timbers’ posts and girts. Mortise and tenon connections connect the girts (girders) to the four corner posts. The corner post has a mortise opening cut through it and the ends of each girt (girder) are cut down in size to fit into the mortise openings. Although large timbers are used to reinforce the three-story structure, they are weakened by this connection. The timber corner posts have holes cut in them and the timber girt ends are cut down to half the size of the original timber at each end. Because of this mortise and tenon connection weakening, the timbers have less load-bearing strength. This connection is the triple-decker building’s structural framework. When investigating most structure failures, it occurs at the connection. The construction element does not break in the middle, but it does break at the connecting points. A structural element, such as a column, girder or beam, rarely breaks apart. They fail at the connection.

If it is necessary to check the stability of a triple-decker during a building inspection, a Fire Officer checks the corners of the building at each floor level where the girts are inserted into the corner post’s mortise. If it is bulging out here, the building may be coming apart at this point or if the corners of the building are not vertical from street to roof, this could indicate a defective mortise and tenon connection. A mortise and tenon connection is the only connection that can be destroyed by termites, fire and rotting. Metal connections are superior.

A post and girt triple-decker can collapse suddenly during a fire when it breaks at the mortise and tenon connection. If this happens, the building can totally collapse in an inward-/outward-type collapse. The first floor wall falls outward and the second- and third-floor walls collapse inward, similar to a falling house of cards. A warning sign of a triple-decker collapse is heavy fire involving the first floor. Upon arrival at a triple-decker building, if fire involves the entire first floor and master streams are required to be used to extinguish fire on the upper floors, it is a warning sign of a collapse. If the triple-decker stands alone unattached or on the end of a row of triple-deckers next to an empty lot, the collapse potential is increased. When an unattached triple-decker building does collapse during a fire, all four sides can collapse simultaneously. If the structure is a corner building, three sides can fail at once. When the entire structure fails, three or four walls and all the floors pancake down, this is called a global collapse.

Air and light shafts

Building and housing codes require a window in every room. When triple-deckers are built in a row, there may be an air shaft built between buildings to provide fresh air and sunlight to interior rooms. The shaft terminates at ground level and is open at the top to allow sunlight down into the shaft and into the rooms of attached buildings. These shafts spread fire from floor to floor by way of the windows opening onto the shaft. The wood window frames of both buildings facing a shaft can ignite during a shaft fire or on a hot night, when all the windows to the air/light shaft are open and flames can spread into several floors of both buildings facing the shaft. This complicates firefighting. You can quickly have fire on all floors, in both buildings, requiring hose-lines stretched to both buildings.

When fire spreads to air or light shafts between two buildings, you must locate the fire origin and have the first line go to the building with the fire and a second line to the adjoining building to protect this exposure. A third hose-line is stretched to any room off the shaft where flame has spread. If there is a report of fire on an upper floor that has spread from a shaft fire, a hose-line is stretched to this point, but a ladder must be raised to this floor to provide an escape for Firefighters in case the stair becomes unusable and they are cut off by fire.

Wood furring and lath

Furring refers to the strips of wood or the process of installing the strips of wood for nailing. Furring is thin strips of wood, usually measuring one by two or one by three inches, used to level or raise surfaces of another material. In

chapter image Fig. 3.4  When fire spreads to air or light shafts between two buildings, you must locate the fire origin and have the first line go to the building with the fire and a second line to the adjoining building to protect this exposure

Wood lath refers to even smaller strips--½ by one inch--which are nailed to the furring underside. Wet plaster is applied to the lath surface, creating the ceiling or wall in the rooms of 19th century triple-deckers. This construction no longer is used in modern triple-decker construction. However, old triple-deckers will be with us for many years, fires will continue to occur in them and Fire Officers must be familiar with this construction.

Today, furring strips may be metal and there is no wood lath used. In both old and new triple-deckers, after a room and content fire, these ceilings must be opened with pike poles to check that fire has not spread to the concealed space above the ceiling. Most fires occur in the older, inner-city rows of triple-decker buildings that have wood lath and plaster ceilings. A Fire Officer must train Firefighters to correctly use a pike pole to open a ceiling of wood furring and lath. If a fire-damaged plaster ceiling is not opened correctly and the furring is pulled down, there could be a ceiling collapse.


A Fire Officer also must train Firefighters to open up furring and lath plaster walls to keep damage to a minimum during overhaul. After a room and content fire has been extinguished in an old triple-decker, causing parts of the ceiling plaster to fall, due to heat or knocked away by a hose stream, the direction of the wood lath can be determined. In an old triple-decker building, the furring strips usually run perpendicularly to the floor beams and the wood lath runs perpendicularly to the furring strips. When pulling a ceiling with a pike pole after a fire to avoid a ceiling collapse, a Firefighter should drive the pike pole hook up through the plaster ceiling with the point and hook parallel with the wood lath. Then move the pike pole one-quarter turn forward, with the hook pointing forward, and with short, sharp strokes, pull the pole up and down, removing only the lath and plaster ceiling between the furring strips and not pull down the furring strips. If you pull down the furring strips, this could cause a large part of the ceiling to collapse on top of everyone in the room performing overhaul. Wood furring also is found on other than triple-decker buildings and other than ceiling construction.


Cockloft is a fire service term defining a concealed roof space above the highest finished ceiling. A cockloft is completely enclosed and located between roof rafters and the suspended ceiling. It extends over all apartments in a building and can be one foot to three feet high, designed to insulate the occupancy from the rays of the sun and cold from snow and ice on a roof.

chapter image Fig. 3.5  When opening lath and plaster ceilings, remove only the lath and plaster ceiling between the furring strips. Do not pull down the furring strips because this could cause a large part of the ceiling to collapse.

A common roof space is different; it is a cockloft that also extends over adjoining buildings. Fire that extends to the cockloft of common roof space is difficult to extinguish because there are no openings to the space, ceilings must be pulled to gain access, the space is too small for Firefighters to enter and there are large amounts of exposed wood in a cockloft, including roof beams, furring strips, wood lath, wood bracing between beams and the underside of the roof deck. This exposed wood quickly provides fuel for a large fire when fire enters the cockloft. In a triple-decker, the cockloft space will extend over all top-floor apartments and if fire enters the cockloft, it spreads over all the rooms in the building and engulfs the entire top floor of the building. And, similar to an attic in a one- or two-story dwelling fire, the firefighting objective is to keep fire from spreading to this large concealed space. Concealed spaces in a triple-decker lead to the cockloft and any fire that extends to a concealed space may spread to the cockloft and must be stopped.

For example, after a fire is knocked down, a Fire Officer immediately must order Firefighters to check the ceiling space above the fire origin by pulling the ceilings above the fire. Fire can spread into the cockloft space several ways: any fire on any floor that enters the ceiling space may spread to the cockloft; any fire spreading up a light or air shaft can burn through the roof eaves at the top of the shaft; any fire from a flaming, top-floor window lapping up into a cornice; and any fire spreading up exterior siding can enter the cockloft at the eaves. The most common way flames spread to a cockloft is flame extending through a top-floor ceiling.

The cockloft has been discovered by the arsonist. The arsonist knows how difficult it is to extinguish a cockloft fire and the great damage a cockloft fire creates, so one arson method is to cut a small hole in the roof and spill accelerant into the opening and ignite a fire here.

Some Fire Chiefs, including myself, believe if fire spreads to the cockloft from a lower floor, the fire strategy was a failure. If fire spreads to a cockloft, the entire building is destroyed. One of the goals beside life safety and extinguishment of the origin of the fire for an IC at a triple-decker fire is to keep fire from spreading to the cockloft.

A Fire Officer must examine the cockloft for the presence of fire any time a shaft fire is extinguished or flames blow out of a top-floor window or spread to a decorative cornice. This investigating Officer must examine the cockloft as soon as one of these fires is extinguished. When fire is suspected in the cockloft space and Firefighters are to open the top-floor ceilings with pike poles, other Firefighters must be in position and ready with hose streams. If fire is discovered in the cockloft, a vent opening in the roof must be cut over this fire to increase vertical fire rise and slow down horizontal fire spread in the cockloft. An aerial ladder must be in place to provide escape anytime a Firefighter operates on the roof of an unattached triple-decker.



Returns are a term describing the side walls of a skylight or scuttle cover opening as it passes through the cockloft space. When an access ladder in a hallway extends from the top floor of a triple-decker to the roof, a four- by four-foot opening passes through the cockloft. Before a skylight or scuttle cover is removed for venting, any pent-up fire may spread into the cockloft through the return walls. After venting and top-floor fire extinguishment, the return side walls of this opening can provide a limited view of the cockloft space when removed. If the returns are broken open with a tool and heavy smoke comes out, this could be a sign fire already has entered the cockloft. After a fire has been extinguished, a Firefighter on a ladder can punch open one of the return walls and with a flashlight, check the cockloft for fire presence. The return opening can offer a quick size-up of a cockloft fire condition and this plaster and repair can be less costly than opening a ceiling or roof.

A triple-decker fire battle plan:

  1. The first hose-line is stretched to the front entrance and up to the fire apartment to extinguish the fire.
  2. The second hose-line is stretched as a backup to the first line and is taken to the floor above if necessary. If the original fire is on the top floor and it appears the fire may spread through the common roof space, the second line may be taken to the top floor of the adjoining row house that is threatened by fire. Here, the ceilings are pulled and the common roof space checked for fire spread. A third line is a backup line in the fire building.
  3. Ground ladders are placed for rescue or window venting that should be coordinated with the advance of the attack hose-lines.
  4. Primary stair venting is accomplished by removing the scuttle cover and/or skylight over the interior hall to release smoke and heat banking up on the top floor. Stair venting allows Firefighters to maintain their position on the top floor and control the interior stair for search and fire extinguishment. This venting should be done as soon as possible. The windows of the fire apartment should be coordinated with the first attack hose team advance to prevent flashover or backdraft. If fire is discovered in the common roof space, a vent opening should be cut in the roof as close as safely possible over the cockloft fire.
  5. The aerial ladder is placed to the roof of the building on the upwind side of the fire. A Firefighter climbs the ladder for roof access and roof venting.

The game-changer

The game-changer is fire in the cockloft or spreading up the outside siding, heading up to the eaves and cockloft. A hose-line must be sent to the top floor of the adjoining building threatened by the common roof space fire. An outside line should be moved into position to cut off flame spread before it reaches the eaves and spreads into the cockloft. Place a ladder at the top floor for Firefighters’ emergency exit in case stairs are blocked by fire.

Triple-Decker Battlespace Casualties

Worcester, Massachusetts, one Firefighter killed and one injured, when the rear of a triple-decker collapsed. NIOSH 2011-30

Chapter 4: Multiple Dwelling Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


The multiple dwelling is a three-family dwelling battlespace that has metal doors, police locks, bolts, chains and long hallways. It takes a lot of guts to move down a smoke- and flame-filled long hallway of a multiple dwelling where it can be fatal to pass a burning room off to one side. If you make it down the long hallway inside the apartment, then you face locked window gates, bars and sealed-up dumbwaiter shafts and because the five- to seven-story structure is higher than the surrounding buildings, if you vent prematurely, you set up a wind-driven fire from window to hallway. If you have to stretch a hose-line up a rusted old fire escape because the interior line cannot advance and flame from a top-floor window is heating the metal cornice, hot, molten lead is raining down on you.

Multiple dwellings can be large apartment houses or tenements, sometimes located in old downtown or inner city sections, with nearby vacant buildings and high fire rates. This battlespace is where urban warfare takes place. The following are construction features found in the multiple dwelling battlespace that a Fire Officer must know about to extinguish fire and survive.


These are small glass windows above each apartment door in a multiple dwelling. They are designed to transfer light from a hallway to an apartment. In older multiple dwellings, there was a roof skylight on the top of the stairway, which brought sunlight into the interior stair enclosure through the center of the stairwell and the transom over the apartment entrance door was intended to extend hallway light into the apartments. Some transoms were designed to swivel open. Today, transoms are illegal. However, some older multiple dwellings still have them. The fire problem with transoms is that they could break from heat and allow fire to spread from an apartment out into hallways and cut off people escaping from above, down a stair.

chapter image Fig. 4.1  Multiple dwellings are the urban firefighting battlespace.


This is wood paneling applied to the lower third part of a wall. Originally, it was applied to the hallways of multiple dwellings. Wainscoting adds fuel to an interior stairway. When building codes started enforcing fire safety in multiple dwellings, the interior stair was required to be a fire-protected enclosure. In new multiple dwelling construction, transoms and wainscoting in public hallways are illegal. Only the stair rail and apartment doors could be wood if they met a required fire rating and the hinges were fitted with self-closing springs. Wainscoting still may be found inside a multiple dwelling apartment and adds fuel to a fire. During overhauling operations, a Fire Officer must have Firefighters remove the wainscoting that is scorched and charred by a nearby content fire. Wainscoting is opened up to check the wall space behind it for fire spread.


Also found in the apartment of a multiple dwelling is wood paneling from floor to ceiling. Wood panel walls and wainscoting make firefighting more difficult because it can cause a flameover. Fire flameover is rapid fire spread over the surface of a wall. Wood paneling also can speed up flashover, when a room suddenly can burst into flame more quickly because a burning wood wall surface does not allow the transfer of heat from the content fire to the upper walls and ceilings, therefore speeding up thermal radiation feedback and flashover. A Fire Officer must know a wood wall surface can flameover and spread fire behind advancing Firefighters, while a flashover can engulf Firefighters searching in smoke.

Self-closing door

This is an apartment door normally held in a closed position by a spring. A self-closing door has spring-loaded hinges designed to close the door automatically after it has been opened. An apartment door is the most important fire protection device in a multiple dwelling. A self-closing door keeps fire from an apartment spreading out to the stairway, trapping people on the upper floors. The self-closing door also keeps smoke and heat in a stairway from entering the apartment.

There is a very effective fire education radio message that says, over and over again, “The door, the door, the door, close the door! It can save your life during a fire.” I cannot tell you how many fatal fire investigations have concluded had the victim closed the door to the room, he or she would have survived.

People do not understand the importance of a closed door during a fire. Even a wood door will stop fire and most of the smoke for a half hour. After one post-fire investigation, a building employee confessed that the occupants of the building would pay several dollars to have the spring of a self-closing device rendered inoperable because if the self-closing door closed behind them when retrieving a newspaper in the hall, it could lock them out.

During a fire in a multiple dwelling when a “defend in place” strategy is being used while the Firefighters extinguish a fire, the Fire Officer must order all occupants to stay in their apartment and close the door. Also, when a fire occurs in an apartment of a multiple dwelling on the lower floor and there is a delay stretching the hose and people are coming down a stair, a Fire Officer must order Firefighters to close the door to the burning apartment until people in the stair descend safely. When the hose-line is in place, personal protective equipment (PPE) is in place and the nozzle bled of air, then the door to the apartment is opened and Firefighters quickly advance and extinguish the fire. Once again, an apartment door is the most important lifesaving device in a multiple dwelling.


It is a horizontal decorative molding that crowns a multiple dwelling. A cornice can be constructed of wood, sheet metal or plastic. When multiple dwellings are built in a row, fire can spread to several adjoining buildings in the cornice. Fire coming out of a top-floor window of one of the multiple dwellings can spread up to a wood cornice and then travel horizontally to one or both adjoining buildings. Even if the cornice is sheet metal, it will have an interior framework of wood and a concealed fire can spread to the adjoining buildings inside the cornice.


Fire that spreads to a cornice also can extend quickly into the common roof space or cockloft. This is another reason a Fire Officer should not allow fire to spread to a cornice in a multiple dwelling. Many building codes require a cornice to be firestopped every 20 or 30 feet so fire does not spread to adjoining buildings by way of a cornice. After a top-floor fire in a multiple dwelling is knocked down, a Fire Officer should have a Firefighter with a hose stream move to the front or rear windows and extinguish any fire burning at the window frames that can extend into a front cornice or roof eaves at the rear, as this will prevent fire from spreading into the cornice or common roof space. After a serious apartment fire has been knocked down, a small fire involving only the window frames may not seem important to exhausted Firefighters, but it is crucial because this small fire can spread to a cornice or cockloft and create much more damage than the original apartment fire. Fire spreading into a common roof space can destroy all the apartments on the top floor.

Fire escape

This is an emergency exit that provides a second means of escape if the interior stair is blocked by smoke or fire. A Fire Officer should know there are two kinds of fire escapes on multiple dwellings--a standard fire escape and a horizontal exit fire escape. A standard fire escape has an access ladder between floors that allow people to go up or down; a horizontal exit fire escape does not have an access ladder between floors. Instead, it serves as an escape for occupants fleeing a fire by allowing them to go horizontally into the adjoining building.

A horizontal exit fire escape is the oldest type of fire escape and is built serving two separate buildings. This type of fire escape quickly becomes overloaded with people because they do not understand how to use it and often the adjoining building windows are locked.

chapter image Fig. 4.2  Fire that spreads to a cornice also can extend quickly into the common roof space or cockloft.

A fire wall between the two buildings served by the horizontal exit fire escape is the protection. People must enter the window of the adjoining building and use the interior stair of this building to go to street level and safety. A Fire Officer should know there will be overloading on a horizontal exit fire escape and order Firefighters to go to the adjoining building, open the window and assist people into the building through the window off the horizontal exit fire escape as soon as possible before the balcony collapses from overload.

A standard fire escape is the most common fire escape found on a multiple dwelling and can be found on the front, side or rear wall of a building. It will have a metal balcony enclosed by a railing, serving the second to the top floor, and a narrow metal stairway at a steep angle, providing access between floors. There will be a moveable sliding vertical ladder (drop ladder) held in place on the second-floor balcony by a pendulum hook.

Upon arrival, a Fire Officer should order Firefighters to lower the drop ladder by using a pike pole to raise the vertical ladder several inches, which disengages the pendulum hook and allows the ladder to drop straight down to street level. This action allows Firefighters to ascend the fire escape and assist occupants descending the fire escape access ladders.

Fire escapes are dangerous, unfamiliar, outside emergency stairs and people on them must be assisted by Firefighters. Occupants should not be taken down a fire escape if the interior stairs are accessible. Once people are below the fire floor, they should be taken inside a window, through an apartment and down the interior stair, instead of down the dangerous fire escape.

chapter image Fig. 4.3  Fire escapes are dangerous, unfamiliar, outside emergency stairs and people on them must be assisted by Firefighters.

In 2015, in Flatbush, Brooklyn, at a five-alarm fire, an occupant fell to his death from a rear fire escape while attempting to escape a fire. When a person is seen on a fire escape during a fire, a Fire Officer should consider the person in danger and order a Firefighter to assist.

There are several features of a fire escape that make them a fall hazard. Fire escapes can be icy and slippery when wet; fire escape ladders descend at a steeper angle than a normal stairway; a fire escape may have only one railing, which makes it difficult to hold onto during descent; and fire escape treads are narrower than a stair tread and, in some instances, two bars instead of a flat metal surface. Rust and decay due to the lack of maintenance cause fire escape treads to collapse under the weight of an occupant or Firefighter use during a fire. A Fire Officer should know that a fire escape is low priority among the victim removal methods used during a fire. The priority of victim removal at a multiple dwelling fire is interior stairway, removal with an aerial platform, removal with an aerial ladder and, last choice, removal via a fire escape.

Gooseneck ladder

This is a vertical ladder from a fire escape to a roof. The gooseneck is the part of the metal ladder that bends over the parapet wall. These ladders are illegal today and found only on multiple dwellings built in the 19th and early 20th centuries. Besides being dangerous, they are unsightly and rarely will be found on the front fire escape; they are found on the side or rear fire escape of a multiple dwelling.

The danger of a gooseneck ladder is its 90-degree, straight-up, vertical position. Unlike a ladder placed at a 45-degree angle, the vertical gooseneck ladder does not allow a Firefighter to balance himself or herself with feet on a rung. Both hands must be used to climb a gooseneck ladder. If there is any moment when a hand is not grasping the ladder, the weight of a SCBA on a Firefighter’s back has a pullback effect. Gravity also pulls a Firefighter off a gooseneck ladder.

Another problem with a gooseneck ladder is that it may be attached too close to the wall, not allowing space between the ladder and wall for a climber’s foot to be placed squarely on the rung, with the ball of the foot on the rung. In this case, only the toe end of a Firefighter’s boot may be used for support, while both hands grasp the rung to keep from falling.

A Fire Officer must ensure that Firefighters assigned to roof operations have slings for carrying saws and forcible entry tools. Slings allow Firefighters to carry equipment over their shoulders and have both hands free for ladder climbing, especially on a gooseneck ladder. One of the factors causing the fall of Chicago Firefighter Christopher Wheatley from a vertical fire escape ladder was insufficient space between the vertical ladder and the building wall. He was unable to place the arched part of his boot on the ladder rung.



This is a structure on the roof built over a stairway, elevator shaft or dumbwaiter shaft. Small multiple dwellings do not have bulkheads and instead have skylights and scuttle covers over interior stairs. A Fire Officer should know that these roof structures should be vented during a serious fire in a multiple dwelling in order to prevent smoke buildup and mushrooming on the top floor. When a fire occurs in a lower floor of a multiple dwelling and Firefighters open the apartment door to advance a hose-line, smoke flows out over their heads and rises up the stair. This smoke accumulates on the top floor and sometimes must be vented at roof level. A Fire Officer should order a Firefighter to vent a bulkhead, scuttle cover or skylight that is located over the stair to prevent top-floor smoke buildup and mushrooming.

Before the benefits of roof venting were known, Firefighters would extinguish a fire on the lower floor and after the fire was extinguished, they would find people overcome by smoke on the top floor from the lower-floor fire. Venting these roof portals also allows Firefighters to maintain a position on the top floor to search and advance a hose-line. Without the roof venting, smoke and heat could bank down and prevent Firefighters from working on the top floor during a fire. Roof venting saves lives and assists fire extinguishment.

When venting a bulkhead structure over a stairway, a Firefighter should force open the door leading to the roof. If heavy smoke comes out of the doorway, sweep the floor inside with a tool, looking for an unconscious victim. If it is possible to gain access to the skylight on top of a bulkhead structure, vent that, too. The forced bulkhead door should be chocked open or the hinge broken to prevent it from closing.

Scuttle cover

This is a wood, metal or plastic hatch cover that provides access to a roof from the top floor of a multiple dwelling by a ladder. On smaller multiple dwellings, there may not be a bulkhead structure but, instead, a scuttle cover and a skylight on the roof surface that can be vented. A Fire Officer orders Firefighters to lift or force off the scuttle cover and glass skylight to vent the roof during a fire. When forcing a scuttle cover, pry it from the exposure #1 (A) side, because this is where the fasteners on the cover underside most often are located. The access ladder and scuttle cover usually are near the front of the building on the top-floor landing and the skylight is centered over the middle of the stair. As long as there is no door enclosing the scuttle cover ladder in the alcove, both of these roof openings effectively will vent the interior stair of a multiple dwelling. When prying up a scuttle cover, try not to damage the coaming, the raised frame around the opening, because it keeps rainwater from running into the building. After a roof scuttle cover or skylight is removed from the opening, a Fire Officer should know the returns--the interior surface of the opening between the roof and the top-floor ceiling—once opened, can provide a view of a cockloft. Any fire or heat buildup in a cockloft can be determined by opening the return walls of a scuttle or skylight opening.

chapter image Fig. 4.4  When prying up a scuttle cover, try not to damage the coaming–the raised frame around the opening–because it keeps rainwater from running into the building.


This is a glass or plastic roof fixture designed to transmit light or air into a multiple dwelling. A Fire Officer should know that a skylight often is positioned over the interior stair of a multiple dwelling. For effective roof venting, have Firefighters assigned the roof operations perform the following tactics:

  1. At a routine, small content fire, opening the bulkhead door may be sufficient and the skylight need not be vented.
  2. At a bulkhead puffing smoke, it is quicker to vent by opening the skylight than to force the door to the bulkhead.
  3. To get atop a bulkhead structure to vent a skylight, use a Halligan tool, lean it against the bulkhead with the forked end down and adz end up and use the adz end as a step to reach a skylight on top of a bulkhead.
  4. After forcing a bulkhead door for venting to keep it open, use a chock on the door or a nearby, loose coping stone to brace it open or break a top hinge.
  5. Where there is a scuttle cover and skylight, vent the skylight first, then the more time-consuming scuttle cover.
  6. To remove a skylight without breaking it, bend the clips on the skylight strap up, then pull it up to allow the glass panel to be lifted without breaking it.
  7. Recommended tools for roof venting are a Halligan hook and a Halligan pry bar.
  8. During salvage and overhauling operations, replace the skylight and scuttle covers and close a bulkhead door.

Spandrel wall

This is the exterior wall surface between the top of one window and the bottom sill of the window above. When fire is lapping out a window, a hose stream is being directed to stop auto-exposure and there is a possibility of injuring Firefighters inside, the Fire Officer of the Firefighter directing the stream should order the stream to hit the spandrel wall section and not go into the window. Splattering water against the spandrel wall can slow flame lapping up from one window to another. The outside hose stream should not be directed in the windows unless an Operations Officer in charge of interior firefighting confirms that all Firefighters have been removed to safety. A Fire Officer also should know that a spandrel wall can be weakened by the powerful, high-pressure master stream and collapse, so Firefighters should not pass beneath the stream to get into the building.


These are two- by two-inch strips of wood, embedded in concrete or brick, used as an anchor to nail down under-flooring for floorboards. If a serious cellar fire heats up a masonry cellar ceiling, it could conduct heat upward and ignite the wood sleepers of the first floor of a multiple dwelling. After a serious cellar fire in a multiple dwelling that has a masonry ceiling, a Fire Officer should examine the first floor directly above the fire for any heat conduction to the sleepers embedded in the concrete. A thermal imaging camera should be used to scan the floor to discover any smoldering in the wood sleepers. If burning sleepers are detected, the finished floor must be cut open and the charred and burning sleepers removed and wet down.

chapter image Fig. 4.5  When fire spreads to the cockloft, an aerial master stream must be placed in position for use if interior attack hose-lines cannot extinguish it.

A multiple dwelling fire battle plan

  1. The first attack hose-line is stretched up the interior stair to the fire apartment. This will be a long stretch, requiring many lengths of hose. All Firefighters at the scene should assist in this stretch. The strategy is to get the first line stretched and charged with water before the second hose-line is stretched. At some apartments, the stair encircles an elevator shaft and must be stretched using a rope to haul the hose-line up to the floor below the fire. The rope is dropped out of a window from the floor below the fire. The nozzle and hose are securely fastened to the rope and the hose is pulled up to the floor below the fire by Firefighters. Sufficient excess hose should be pulled into the window onto the hall for an advance up the stair, down the hall and through the apartment. This should be at least three lengths of hose. The hose is secured with a hose strap at key points so it does not slide out the window. If necessary, the entire first-alarm assignment must be dispatched to get the first line in operation.
  2. The second line is stretched to back up the first line. This hose-line may be needed on the same floor as the fire apartment. Most of the time, it will be used on the fire floor.
  3. A portable ladder may be placed at the fire escape to remove people. An aerial ladder may be used to advance hose-line.
  4. When the fire occurs in a top-floor apartment, the roof should be cut to provide vertical venting for the burning apartment and stop horizontal fire spread in the cockloft.

The game-changers

The game-changers are fire in a shaft, wind-driven fire or fire in the cockloft. When fire enters a shaft, a second hose-line must go to the adjoining exposed building to prevent the shaft fire from spreading to the building. A report of a wind-driven fire dictates that interior forces back out, close the door and advance an outside line through the window with the wind. An outside aerial master stream may be required to extinguish fire in a multiple dwelling cockloft and top floor.

Multiple Dwelling Battlespace Casualties

Bronx, New York, three Firefighters trapped and killed, jumping from fourth floor of multiple dwelling. NIOSH 2005-03.

Additional reading

Forcible Entry Reference Guide, Techniques and Procedures, FDNY, Captain John Vigiano

Chapter 5: Warehouse/Loft Building Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A loft building is a former manufacturing building that was built during the past century in medium to large cities. Some have been converted for use as storage warehouses, apartment condominiums or retail stores. These are called “hard lofts,” century-old structures converted to any kind of residential, public or commercial use. There are “soft lofts” that are new residence structures built with large, open spaces, such as those found in old loft buildings. The warehouse loft building battlespace structure that is our concern is the century-old loft building that is a warehouse, apartment condo, office or retail store. The use of the building does not matter; it is the century-old structure that is our deadly battlefield.

After manufacturing went south and overseas, loft buildings were left vacant or became dilapidated, old storage buildings, stuffed with baled goods or heavy machinery. This Type III ordinary or Type IV heavy timber buildings, with large, open floors and cast-iron columns, were not maintained, became dangerous, vacant and subject to arson for profit. These 19th century relics remain in the downtown urban centers of America and may be disguised as artist studios, condos or stores, but they are dangerous, rotting, rusting and dried-out old wood and brick structures.


The loft building battlespace can be identified on the outside by its rusted, old fire escapes, with a contraption called a counterbalance stairway of steel cables, hanging weights and a movable horizontal moving ladder. The inside is worse; you climb a creaking, “straight run” stair, rising from street level straight up to the top floor and if you open a door to the side, you see a large, open space with high ceilings, cast-iron columns, an open elevator shaft and tons of high-piled, heavy-baled cloth or cardboard.

It gets worse if you go down. This building may have a level below grade called a cellar and sub-cellar with walls of jagged, black foundation stone. First, you descend a narrow, wood-enclosed level below grade, then down another set of stone steps to the second underground level into a moldy, stale, unvented dark area. Fortunately, there are only a few of these century-old loft buildings left remaining in a downtown area and they may be renovated, called historic buildings or used as artist studios, but they still have a century-old infrastructure prone to burn and collapse.

Some Firefighters say the letters of LOFT stand for Large Old Firefighter Trap. These archaic buildings create a deadly environment for unsuspecting Firefighters: cast-iron columns; unprotected floor openings; unguarded, open elevator shafts; large, potential fire areas; high ceilings that allow flame to spread overhead; sub-cellar dungeons; suspended ceilings that collapse like a net; shiny, thick, cement terrazzo floors covering rotted wood floors; and rusty, old, counterbalance fire escapes with heavy metal weights that collapse when used.

Loft building storage use has been replaced and located out of town in new, dangerous structures--the big box stores or distribution centers. Some loft buildings have been declared historic structures and will be with us for another century. In New York City, they are disguised as fashionable artist residences and have high-end retail stores on the first floor, but they are still century-old loft buildings with sub-cellars. Following are some of the deadly construction features of the loft building battlespace.

Cast-iron columns

Cast iron is an alloy of iron containing so much carbon that it becomes brittle and cannot be bent or shaped; it can be shaped only by casting. Used mostly as columns in commercial buildings, cast iron has great compression strength, but no ability to resist tension loads. Cast iron was used for columns in the structural framework and, on rare occasions, for decorative facades of older commercial buildings in New York City and Chicago.

In the early 20th century, cast-iron buildings collapsed and killed many Firefighters. It was said that cast iron, when heated by a fire and then struck with cold water from a hose stream, would collapse. However, research of structural failures during fires revealed the cause of collapse was not heating and cooling with hose streams, but due to improper casting. The cast column and decorative cornices and front walls were designed to have uniform thickness throughout and this was not always the case. Post-fire investigations identified uneven thickness of a column or façade as the collapse cause. For example, a broken column examined during an investigation showed a column wall thickness of one inch on one side and only one-half inch on the other side.

Today, cast iron rarely is used in structural framing and never for a building facade. Steel has replaced cast iron as a column. However, thousands of older, now historic, commercial buildings with cast-iron columns and decorative cornices exist in the older, center city areas. Cast-iron columns still support wooden girders of old commercial buildings and Fire Officers now issue a violation order to protect it with a fire-resistant covering.

chapter image Fig. 5.1  Loft buildings are a deadly firefighting environment.

When fire occurs in a commercial building with a cast-iron façade, Fire Officers should order collapse danger zones to protect Firefighters. Anytime a cast-iron column or façade is discovered during a fire size-up, the Incident Commander (IC) should be notified. This important information can influence his or her firefighting decisions.

Counterbalance stairs

Counterbalance stairway fire escapes are found on the exterior of commercial buildings. A counterbalance stairway is a complex fire escape that has movable metal stairs designed to provide access between the lowest fire escape balcony and street level. It is designed to remain in a raised position by cables and counterbalancing weights and pulleys.

During a fire, people leave the upper floors, descend the fire escape and on the lowest level, there is a stair leading to the sidewalk, supported by a counterbalanced weight system. To operate the counterbalance stair, a Firefighter with a pike pole moves a lever and pulls down the end of the counterbalance stair. Once the stair is resting on the sidewalk and people descend, their weight overcomes the weight of the steel counterbalance weight that was holding the stairway in the raised position.


A Fire Officer should know that a counterbalance stairway fire escape is dangerous to operate because the counterbalance weights, steel cables, pulleys and even the entire movable stairway can break apart and collapse down to the street. Many of these heavy metal counterbalance stairs and weights have not been tested or operated for decades. Several hundred pounds of rusted metal either are attached to one end of the fire escape stairway or held up by a pulley and steel cable against the side of the building, ready to collapse when moved. These counterbalance weights sometimes are hidden from view in a tin covering above the fire escape.

There have been incidents in which the entire metal stairway has collapsed onto the sidewalk or a heavy metal weight holding up the counterbalance stair has broken from a cable and fallen to the street. There also have been instances where a steel cable and pulley holding the cast-iron weights have broken off a wall.

chapter image Fig. 5.2  Prolonged fire burning on two floors is a signal to change strategy to a defensive exterior attack.

A Fire Officer must know when arriving at a fire and people are awaiting rescue on the lowest balcony of a fire escape with a counterbalance stairway that it is safer and more effective to order Firefighters to use a fire department ground ladder instead of the counterbalance stairway to remove people. Even better, a Fire Officer should order a Firefighter to climb up the ladder, calm people and take them inside a second-floor window and down the interior stairs.

Unprotected elevator shafts and floor openings

Old commercial buildings have unprotected elevator shaft ways and floor openings. Elevators have manual, seethrough scissor gate protective doors on each floor and window opening, leading to the elevator shaft way. The scissor gates may not always be closed. Also, there are floor openings where you would not expect: elevator shafts, light shafts, conveyor belt shafts and trash chutes and all create fall hazards and also spread fire from floor to floor, which can trap Firefighters searching upper floors. These floor openings are not enclosed as required; safeguards sometimes are removed or left open at night or obscured or destroyed by smoke and flame.

A great danger is an elevator shaft located at the outer wall of a warehouse factory or storage building that has windows opening directly into the shaft providing light. Firefighters climbing aerial ladders entering windows have fallen into elevator shaft ways, thinking they are stepping onto a floor through the window. These windows opening into shafts must have warning signs outside near the window, indicating shaft way. This sign is to warn Firefighters climbing ladders and notify them that the nearby window opens into a shaft, not a floor. These signs may be missing or painted letters faded from age.

Anytime Firefighters climb through a window of a commercial building, they should check with a tool by probing for a floor before entering. Firefighters even can drop a tool, listening for the sound of it striking the floor.

When operating on a roof at night, there are other open shafts that are great dangers. When a Firefighter climbs over any short parapet wall on a commercial building roof in darkness or blinded by smoke, he/she may not be climbing to another section of roof, so ensure there is a roof on the other side of the low wall and not an open shaft. Again, Firefighters should probe with a tool before climbing over. There may be several bulkheads enclosing stairs, penetrating the roof of a commercial building. These small structures have doors that sometimes are forced open for venting or entry by a Firefighter on a roof. Sometimes, the bulkheads are at the top of elevator shafts, not stairways. Again, at night or in smoke, when forcing the door in the roof bulkhead, do not enter the opening until you confirm there is a floor.

Fire Officers must train Firefighters working in old commercial building districts to be cautious and identify the hazards for them. Most importantly, show Firefighters the searching technique of using a tool to probe ahead when searching in smoke or at night. Firefighters advancing hose-lines without a tool to probe must use an outstretched leg, feeling for unprotected floor openings when moving forward during poor visibility.

chapter image Fig. 5.3  A counterbalance stairway fire escape is dangerous to operate because the counterbalance weights, steel cables, pulleys and even the entire movable stairway can break apart and collapse down to the street.

Structure hierarchy

A Fire Officer must know there is a hierarchy of a ware-house/factory/storage structure and amount of destruction during a collapse depends on the first part of this structure hierarchy to fail. Four important structural elements in the hierarchy of an ordinary or heavy timber commercial building are: bearing walls and columns, girders and beams. The higher the first structure to fail is positioned in the hierarchy, the greater the collapse destruction.

For example, if a bearing wall or column fails, there will be major destruction; everything it supports, such as girders, floor and roof beams will crumble, too. If a girder fails, it will trigger collapse of supporting floor or roof beams. When a section of floor or roof fails during a fire, it may not trigger a progressive collapse of other structure members. A progressive collapse occurs when failure of one structure causes the failure of an interconnecting member. When a bearing wall or column collapses during a fire, it definitely will cause a progressive collapse and even may cause a global collapse. A global collapse occurs when the entire structure collapses and nothing is left but a pile of rubble.


A Fire Officer must know when a column on the first floor appears to be distorted or shifting during a fire. This has great significance to the entire structure and all the Firefighters in the building and on the roof, not just Firefighters in the surrounding area of the column. A Fire Officer must notify the IC of this structure weakness.

Large, open floor area

A dangerous feature of a warehouse, storage, factory and loft building is the large, open interior floor space. A warehouse, factory and storage building require the large, open space for storage of content. They must have space for materials and machines and be able to view people for supervision.

A Fire Officer must know that a large, open floor space can allow development of a fire beyond extinguishment with small-diameter hose used in a typical residence building fire. A residence building has floors broken up into small units and partition walls to break spread of fire. Small spaces have small fires; large, open spaces of commercial buildings have large fires. A fully involved, large, open floor fire will overwhelm a small, 1¾-inch-diameter hose stream. Small streams turn to steam and do not have sufficient cooling effect. In a commercial building, a large, 2½-inch-diameter hose is required to ensure fire extinguishment.

chapter image Fig. 5.4  Cast-iron column supporting a loft building structure.

Most Fire Officers agree that Firefighters using a large, 2½-inch-diameter hose stream can extinguish fire in a roughly 2,500-square-foot burning area. Two hose-lines can handle a 5,000-square-foot area. Beyond that floor size, there must be automatic extinguishment to protect the building. If the commercial building has a standpipe, the first line should be hose carried up by Firefighters and connected to the floor below the fire. If a building also has an automatic sprinkler system, a hose-line should supply the sprinkler Siamese after the standpipe is supplied. Sprinklers are more effective than a handheld hose-line. But the standpipe must be supplied first to protect Firefighters.

When there is no standpipe or sprinkler system, a Fire Officer should order Firefighters to stretch 2½-inch hose to fight a fire in a commercial building fire. If a 1¾-inch hose is stretched and the fire not extinguished, the fire company can be criticized and blamed. A 2½-inch hose-line with 1⅛ - or 1¼-inch nozzle can deliver 250 or 300 gallons per minute. This is maximum water delivery by a handheld hose-line. A hose team will need all the water it can get to extinguish a commercial building open floor fire.

The reason Firefighters stretch 1¾-inch hose-lines in residence buildings is because this occupancy will have small rooms, limiting the size of a fire and, in an emergency, Firefighters temporarily can close doors to restrict fire spread. This safety tactic is not possible in a commercial building with a large, open floor area. Mobility is not important in a commercial building fire, but the reach of the large water stream is.

Search and rescue in a large floor area is more dangerous because it is impossible to use the standard organized search procedures, such as keeping in touch with walls while advancing in smoke or darkness. Disorientation, which is loss of direction due to loss of vision, is more of a danger to a Firefighter searching in a large, open area than in an area broken up into small rooms. Firefighter fatalities caused by being caught and trapped by sudden flashover when searching is a great risk because there are no rooms to take refuge in and in a commercial building, the travel distance to safety of an enclosed stair is greater.

chapter image Fig. 5.5  Floor openings are not enclosed as required; safeguards sometimes are removed or left open at night, obscured or destroyed by smoke and flame.

Fire Officers must order Firefighters to use search ropes when entering a large, open floor to search. A ½-inch-diameter search rope 75 to 100 feet long, which can be clipped together to increase search distance, should be tied to a secure object, such as a stair railing, and played out as Firefighters enter a large, smoke-filled floor area when searching for the location of a fire.

A Fire Officer should schedule pre-planning visits of the fire company with the building management. During a pre-planning visit, Firefighters should note the floor layouts and hazards of commercial building occupancies. This knowledge will provide some safety and make Firefighters more effective during a fire operation.

High ceilings

Warehouses, factories and storage buildings also have high ceilings created by the large, open space needed to store the maximum amount of content and allow large machines to function. A Fire Officer of an aerial ladder company must know the different building floor heights to calculate the reach of a ladder when raising it to a window for rescue. Fire Officers know the building floor heights will vary.

For example, a modern residence building floor height will be eight feet; an older residence building can have 10-foot-high floors and commercial building floors can be 12 feet or higher. A building’s floor height also is important for interior search and hose stream firefighting. In a high ceiling occupancy, a Fire Officer must know flame and heat can build up at ceiling level and not be detected by Firefighters operating upright at floor level. In a typical, eight-foot-high ceiling in a residence, smoke and heat quickly bank down to the floor area and serve as a warning to Firefighters the fire is severe and flashover could occur. This warning is not as quick in a high ceiling commercial building floor area.

Super-heated smoke or pre-flashover conditions—rollover--can build up above Firefighters without their knowledge in a high ceiling occupancy. Firefighters have been trapped searching in a building with a high ceiling because flashover suddenly occurs without warning or fire flows behind them in the higher reaches of the ceiling.

In a typical, eight-foot-high ceiling residence building during a fire, a Firefighter searching in smoke sizes up a fire by how far down he/she has to crouch to get below a built-up heat level. The lower the smoke and heat, the lower the crouch and the more serious the fire. Smoke and heat buildup is rapid when a ceiling height is only eight feet; a high ceiling delays notice of hot smoke and flashover buildup. If a flashover suddenly occurs above Firefighters’ heads, radiated heat quickly flows down on them at floor level. If this happens, they will have to run for their lives with no cover over their heads. They can be beyond the point of no return if the travel distance to a stair enclosure is too great. A 100- by 100-foot warehouse floor with exits at each end can allow flashover heat to overtake them before escape.


A high ceiling with flashover conditions were leading factors in the death of FDNY Firefighter Walter Smith, Ladder Company 24, in a Macy’s department store fire. When searching for the location of the fire, super-heated smoke at ceiling level descended upon the fire company and flashed over. As everyone scrambled to escape, Firefighter Smith became disoriented and missed the way to safety.

chapter image Fig. 5.6  A cellar is a below-grade area with a floor height more than one half below street level; a sub-cellar is a floor area below a cellar.

In 1998, two Chicago Firefighters were trapped and killed inside a high ceiling truss roof tire service center in a similar manner. When searching inside a large floor area, undetected fire and super-heated smoke built up over their heads and suddenly ignited. Chicago Firefighters Patrick King and Anthony Lockhart lost their lives. Armed with this tragic information, a Fire Officer should know that high ceilings mean high risks.


Cellars and sub-cellars contain the most hazardous materials of a building. Fuel oil storage, explosive natural gas, high-voltage electricity, toxic chemicals, asbestos, paints and thinners are found in large and small quantities in a commercial building. Anything that the owner wants out of sight or cannot dispose of is stored below grade.

A Fire Officer also must know that a cellar and sub-cellar are the most hazardous spaces in a building. A Fire Officer must be able to identify the below-grade spaces accurately to give a correct size-up to command. A basement is a below-grade area with a floor height one half or less below the street level. This is important because in most building codes, a basement is considered the first floor and, by law, may be habitable. A cellar is a below-grade area with a floor height more than one half below street level; a sub-cellar is a floor area below a cellar.

People are not allowed to work or sleep in a below-grade cellar. Sub-cellars are the most dangerous below-grade areas. Sub-cellars were built beneath 19th and 20th century-old commercial buildings to add space or created when street levels were changed.

Some dangerous construction features of a sub-cellar include limited access, with only one sub-standard, narrow, wooden stair leading to the sub-cellar; no windows to vent smoke and heat of a fire; when a fire occurs, it will be a delayed alarm, because this area is not occupied continuously; because there is limited ventilation portals, there can be a smoke/backdraft explosion; toxic gases, such as carbon monoxide, quickly build up during a sub-cellar fire; and limited drainage allows water accumulation from hose streams or sprinklers and a cellar or sub-cellar can become a watery grave for a

chapter image Fig. 5.7  A century-old loft building suspended ceiling collapse.

Firefighter rendered unconscious.

A Fire Officer must know how to protect Firefighters descending into a sub-cellar. For example, Firefighters must wear breathing equipment when descending a narrow stairway leading to a below-grade area, even if smoke is not visible. Toxic gases can be colorless and odorless. A Fire Officer must call for electric-powered fans to be used for fresh air input and to exhaust smoke. If initial hose-line attack extinguishment is not possible or is unsuccessful, a Fire Officer must have a defensive strategy.

High-expansion foam is the most effective defensive firefighting for a below-grade area. A below-grade area will contain high-expansion foam within its walls and no plywood barriers will be needed to confine the foam in the fire area. High-expansion foam may not fully extinguish, but it will subdue the flame and heat, which can provide Firefighters time to evacuate upper floors and, in some instances, it can reduce flame and heat so a fire company then can advance down to the cellar with a hose-line to extinguish the fire.

Content matters

Loft buildings often are storage buildings. Storing floor to ceiling baled goods often is the only purpose of these buildings. Fuel of a burning building is provided by the structure and the content. The structure fuel is constant and does not change, but the content fuel load changes drastically over the lifetime of a building. In a loft building, knowledge of the type and amount of content fuel inside a building are critical for an accurate size-up.


Content was a severe fire hazard in a loft building area of New York City called

“Hell’s Hundred Acres.” This area housed century-old, dilapidated warehouses, factories and storage buildings that burned, collapsed and killed Firefighters. The real problem of Hell’s Hundred Acres was the content stored inside the buildings, not just the old buildings themselves. The typical content in a loft building is classified as heavy content load. Each floor can hold tons of combustible, rolled cloth, baled rags, stacked paper and heavy, noncombustible material, such as printing and textile machines, electronics, wire, computers, plastics, plumbing supplies and carpet showrooms. The old wood floors are sagging under the heavy material inside.

Floor load signs must be posted by the Building Department. Storage buildings should be protected with automatic sprinklers and sprinkler heads require a distance of 18 inches below piping to work effectively, while Firefighter hose streams require three feet of space above stock for hose streams to have an effective reach.

The type and amount of storage inside a loft building can be a game-changer. Baled goods of paper, rags, carpets and bolts of cloth all absorb water and collapse floors; heavy machinery speeds up collapse of floors during fire destruction. The many signs showing maximum floor loads should be a warning to us during a fire. A Fire Officer always must consider type of content stored in a loft building.

Suspended ceilings

Century-old commercial buildings have suspended ceilings of stamped decorative sheet metal or an acoustic tile. This large ceiling is suspended by wooden furring strips. If the wood hanger strips burn and are weakened by fire, the entire ceiling can collapse. As a new suspended ceiling is constructed, the old ceiling is left up.

Over the years and several renovations, there may be several suspended ceilings, one below another, and each old ceiling has holes through which fire may penetrate and spread. When Firefighters examine a ceiling for fire spread, all of the suspended ceiling must be opened and the space above examined. The space above a suspended ceiling also may contain electric computer cable with combustible insulation covering. If fire spread to this space, there will be a smoky fire and a ceiling collapse danger. The wood furring strip supports quickly can weaken and the ceiling fall on Firefighters like a net.

The ceiling grid system of sheet metal or acoustic tile can weigh several hundred pounds and when it collapses, there are four outcomes for Firefighters trapped below

  1. Firefighters can be trapped in a lean-to void and be able to crawl out from under the ceiling through a void created by furnishings.
  2. An unlucky Firefighter can be pinned to the floor by the ceiling.
  3. A Firefighter can be trapped inside a small, sealed space beneath the ceiling and killed by combustion products.
  4. A Firefighter can break through the ceiling and be engulfed in flames.
chapter image Fig. 5.8  A 1958 collapse of a storage loft building on Wooster Street in “Hell’s Hundred Acres,” NYC, killed four Fire Patrolmen and two FDNY Firefighters.

A Fire Officer must know after a ceiling collapse there is rapid increase in fire and the injury a Firefighter receives will come from smoke and flame following the collapse, so a hose-line quickly must be directed to extinguish any fire. At the moment of collapse, there will be a compression of air space below the falling ceiling, a vacuum in the space above the ceiling and air will rush into the space above the fallen ceiling, igniting any combustible gases. Combustible gases that have built up above the ceiling suddenly will ignite during the collapse due to the inrush of air.

A Fire Officer must know to prevent Firefighters from being trapped by suspended ceiling collapse in a commercial building. For example, when entering a large floor area near a doorway, first have a Firefighter check the space above the ceiling for fire by using a pike pole to open up a small area of ceiling or lift a ceiling panel. The most important method of protecting against a suspended ceiling collapse is to extinguish the fire before it spreads through the ceiling to the concealed ceiling space above. Extinguish a content fire before it spreads to the structure. A Fire Officer must order Firefighters to open up the ceiling above the fire as soon as a fire is extinguished and check for fire in the ceiling space. Open up until there is no char in the wood or metal above the suspended ceiling.

Terrazzo floors

A terrazzo floor is composed of polished marble chips poured over several inches of cement, usually built over an old wood beam floor to give an occupancy a modern, sturdy effect. Terrazzo is the name of the marble chip surface set in the cement. This floor usually is found on a first floor, near the entrance, and its purpose is to enhance the initial impression of visitors.


Fire experience has shown a terrazzo floor can be deadly during a fire for several reasons: a terrazzo cement four- or five-inch base increases the dead load of an old wood floor; cement and terrazzo insulate the heat of a cellar fire below it; and terrazzo conceals floor that is being weakened by fire below it.

The supporting wood floor beams below the terrazzo can burn and fall away and yet the terrazzo can look stable. In this instance, there will be no warning signs of floor collapse. Smoke and heat from the cellar fire will not rise up through a terrazzo floor as they would through a wood floor. There will be no warning signs of a fire-weakened floor, such as a spongy or sagging feeling. When a terrazzo floor collapses after the wood beams below have burned away, it falls in large sections, similar to large chunks of ice collapsing in a partially frozen lake.

Terrazzo floors usually are found in commercial buildings, places of worship, restaurants, hallways, lobbies, bathrooms, kitchens and stores. A Fire Officer should consider a terrazzo floor a collapse danger. A Fire Officer may detect an unstable terrazzo floor above a serious fire by spraying a small stream of water over a hot terrazzo floor; if it turns to steam, it may indicate a serious cellar fire below.

A loft building fire battle plan:

  1. Some loft buildings have standpipe systems; others do not. An IC must determine this on arrival and order the first hose-line stretched or rolled-up hose carried up to the floor below the fire, connected to a standpipe outlet and stretched up to the fire floor. A century-old standpipe Siamese connection may break apart when pressurized.
  2. The second hose-line will be required to back up the first line. The floor areas of heavy timber buildings are large, open spaces and two hose-lines will be required to extinguish a fire.
  3. Ground ladders may be placed at windows for rescue or venting and they should be used instead of a counterbalance ladder to remove people from a fire escape. Venting should be coordinated with the hose-line advance to reduce chance of flashover, backdraft explosion or rapid fire growth.
  4. An aerial ladder should be positioned for possible master stream attack if interior firefighting fails. A Firefighter should remain with the ladder controls on the turntable in case a civilian or Firefighter appears at a window and must be rescued.
  5. Because of the collapse history of loft buildings in New York City and other cities, there is a rule of thumb used by veteran ICs that states, “Prolonged burning of fire on several floors is a collapse danger and withdrawal of Firefighters must be considered.” The district in New York City of predominant loft buildings, called Hell’s Hundred Acres, has been converted to high-priced artist studios and is called SOHO–south of Houston Street–but the century-old buildings still burn and collapse.  
  6. Cellar and sub-cellar fires in loft buildings require the use of high-expansion foam instead of sending Firefighters underground or using cellar pipes. High-expansion foam is messy and time-consuming. It slows growth enough to facilitate mop up and extinguishment with hose-lines or provides time for exterior master streams to be positioned around the structure for final extinguishment.

The game-changer

Cast-iron columns, heavy storage content, prolonged fire on two floors and cellar fires are game-changers in a warehouse/loft building. Cast iron does not bend or distort; it shatters and causes a global (total) collapse. Manufacture of cast-iron column thickness is always in question. Consider the content stored inside a collapse danger and two floors of fire as a warning. Below-grade fire requires indirect firefighting with high-expansion foam. A loft building and cast-iron columns make for a deadly battlespace.

Warehouse/Loft Building Battlespace Casualties

Four Seattle, Washington, Firefighters died in a warehouse floor collapse. United States Fire Administration USFA-TR--077, January 1995

Chapter 6: Place of Worship Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A place of worship battlespace does not comply with fire, building or life safety codes. This holy structure is the most dangerous building in a community. If it were not considered a sacred structure, it would be condemned, ordered shut down, vacated with an order to install sprinklers and smoke detectors and provide a 24-hour watchman. The ceiling is higher than our hose stream reaches; the open space allows a fire to grow beyond our extinguishing capability; it has a massive truss roof; flammable decorations and tapestries; the flame spread rating of waxed and varnished covered wood walls is beyond acceptable limits; it has hundreds of open flame burning candles; and no supervisory management on-scene.


During an inspection, a Fire Officer should have a frank discussion held with the person in charge, explaining reasons why manual firefighting is not successful, stating the construction features that prevent fire extinguishment and recommending automatic sprinkler systems and smoke detectors where needed. I read in the New York Times many years ago about an English Fire Chief saying to the Bishop of an 11th century Protestant cathedral, “Your Holiness, Firefighters can do only one of two things if fire occurs in this holy place. We can save the roof if we break the stained-glass windows and vent smoke or we can save the stained-glass windows if we let the roof burn off.” The Bishop answered, “Save the stained-glass windows and let the roof burn off.” What the Fire Chief forgot to tell the Bishop is that we cannot do either one. Fire experience has shown venting the stained-glass windows will not effectively remove the smoke, heat and flame from upper portions of the high ceilings and the roof still will burn off. He also should have told the Bishop when the roof burns, it sometimes can collapse and push out the side walls. The following are some of the battlespace construction features that make firefighting in a place of worship difficult and dangerous.

High ceilings

The high ceilings of a church, synagogue or mosque are beyond the reach of a Firefighter’s hose stream discharge of 30 to 40 feet. This height allows heat and flame to spread across the ceiling of the large assembly area and up into the attic as the hose stream falls short of cooling the upper ceiling area. Firefighters at floor level will be unaware of the fire spread because it is taking place high above their heads and it will be obscured by smoke covering the area.

The hottest area of a burning room is always at ceiling level. Firefighters directing a stream into a room must aim the water at the ceiling to cool off the rising heat accumulating there. Standard operations for Firefighters are to direct the nozzle upward so the stream strikes the ceiling, breaks up and splatters downward in all directions. “Over your head and all around,” describes how to advance an attack hose-line into a burning room. If the ceiling fire cannot be extinguished, the plaster ceiling and large lighting fixtures will collapse down on Firefighters.

Most fires start at ground level. However, the smoke, heat and flame quickly rise up and accumulate at the ceiling level. At such high ceiling levels, flame can spread behind advancing Firefighters and cut off their escape. Or, smoke at ceiling level suddenly could ignite in a flashover and if venting is limited, super-heated smoke at ceiling level can explode in a backdraft.

chapter image Fig. 6.1  A place of worship need not comply with fire codes, building codes or life safety codes.

Firefighters fighting fires in residence buildings are unfamiliar with the hazards of high ceilings because here, the ceiling is only eight to 10 feet above floor level, causing smoke and heat to quickly bank down and warn Firefighters of the seriousness of the fire. In a place of worship, the smoke and heat will not reach the floor level. The high concave ceiling in a place of worship acts as a “heat sink”; that is, it allows heat, smoke and fire to accumulate above the heads of Firefighters. This heat sink effect confuses a Firefighter’s size-up.

In a nutshell, high ceilings prevent a hose stream from extinguishing fire, create conditions for flashover and backdraft explosion and can cut off Firefighters’ escape, with fire spreading over their heads and preventing them from sensing the seriousness of fire and flame spread at floor level.

Large, open spaces

The assembly areas of a church, synagogue and mosque are too large for Firefighters to extinguish a fire with hose-lines. When fully involved, there is too much fire and heat and a typical hose stream’s reach of 30 to 40 feet operated from a doorway will not reach all the interior spaces. This large space can contain a massive quantity of flame and heat that evaporates a hose stream and continues to spread. This large fire can turn 250 gallons of water into steam and not be visibly reduced in size or temperature.

Fire protection engineers and building code officials understand there is a relationship between size of fire and successful firefighting and they require large open spaces exceeding 5,000 square feet to be protected with automatic sprinklers. Among Firefighters, there is an unwritten rule that states a standard hose stream of 2½-inch hose with 1⅛-inch solid bore nozzle can extinguish no more than 2,500 square feet; and two 2½-inch hose-lines 5,000 square feet. A place of worship measuring 100 by 200 feet can have 20,000 square feet of open space.

chapter image Fig. 6.2  The high ceiling of a place of worship is beyond the reach of a Firefighter’s hose stream of 30 to 40 feet.

A Fire Officer must explain to the person in charge of a place of worship that manual firefighting cannot quench a fire in such a large open area. Similar to requirements for commercial structures, an automatic sprinkler system is required in a place of assembly to prevent a small fire from growing and filling up the large space. Smoke detectors also are necessary to provide early detection and avoid delayed alarm, leading to a large fire.

Concealed spaces

Even though they look like stone structures, a places of worship can be ordinary, brick and joist, Type III construction. The exterior may be of stone. However, the structure is a lumberyard enclosed with four stone walls. The recurring fire spread fire problem of a Type III, ordinary constructed building is concealed spaces and, like any Type III building, the large concealed space is the attic or cockloft. The interior walls are plaster, with a surface imprinted to look like stone, but if you break it, you find it is made of plaster and wood lath. Behind these walls are wood studs and voids and combustible spaces that lead up to a large attic. Don’t be fooled; the interior is sculpted to appear like stone, but is plaster and wood and the strategy in a Type III building as soon as you knock down a fire is to quickly open up the walls and check for concealed fire spread. Then, get a Firefighter up to the attic and check this area for fire spread.

When you conduct a pre-fire plan inspection of a place of worship, one of the most important tasks is to locate the stair leading to the attic. This stair is usually in a remote location and difficult to find. You can save time searching for its location if you have identified it in a pre-fire plan.

After an Incident Commander (IC) is notified a fire is knocked down, the next order should be, “Get to the attic space and check for fire spread.” If there is a custodian at the scene, have him lead you to the stair passageway or circular stair leading up to the attic. Up in the roof space there will be more combustibles: a wood walkway extending from front to back of the attic, large wood trusses supporting the roof, the underside of roof decking and bent wood lath strips holding up an arched or vaulted plaster ceiling 50 to 100 feet above floor level.

Also in the attic at the front or rear enclosure walls will be a small window or vent. During a pre-plan inspection, the inspector should determine where this opening is located in the façade or rear wall of the attic. This small window or louvre vent opening can assist Firefighters to quickly assess if fire has reached the attic space. From a tower ladder, Firefighters may remove the window or opening cover and check for fire or smoke. Smoke coming from this opening does not always indicate fire, but it can suggest further investigation.

In some instances, this small attic vent is positioned above the large, decorative rose window and it is important to understand these portals give access to very different areas. The rose window opens up into the assembly area below the ceiling and the attic vent above opens to the attic area above the ceiling. An aerial stream directed here could collapse the ceiling below from water weight. An IC must determine if the window into which an aerial master stream is directed serves the attic or the upper reaches of ceiling space where the fire is spreading. The general rule is that a master stream should not be used when interior firefighting operations are in progress.

chapter image Fig. 6.3  Don’t be fooled--the interior of a place of worship is sculpted to appear like stone, but is plaster and wood and a Type III building.

Flammable interior spaces

The inside surfaces of walls and ceilings--drapes, curtains, tapestries, rugs, paneled walls, altar, wood seats, dried flowers, hay and palm leaves--can be highly flammable. This combustible interior would not be permitted in any other occupancy. In a place of worship, there is no flame spread limited to the interior spaces.

After attending a memorial service in a church and noticing what seemed like sparkling, bright mosaic tiles, I later that day asked the Fire Department Chaplain assigned to the church if new stonework had been installed. He answered, “No, the entire interior of the church was cleaned. There was 100 years of wax residue from the burning candles over the surface of everything.” This is another reason for early detection and quick interior hose-line attack, because flame can spread rapidly over the wax-coated interior surfaces.


Flame spread defines the burning characteristics of building materials and a building’s interior. It is measured on a scale of 0 to 100; asbestos is 0 on the scale of flame spread and red oak is 100 on the scale of flame spread. A Class A or Class I flame spread rating must be in the scale of 0 to 25; a Class B or Class II in the scale of 26 to 75; and Class C or Class III, 76 to 200. Interior flame spread should be Class A or B. The flame spread rating of a place of worship, covered with wax film, could be more than Class C and up to 500. A place of worship should have an early warning smoke detector system to notify the local fire departments quickly because fire can spread rapidly.

Truss roof

A place of worship often has a truss roof that provides a large interior space without columns obstructing the center seating area. A truss is a long-span roof system. A traditional place of worship will have a timber truss roof and a modern place of worship will have lightweight wood trusses.

The fire service has a long and deadly history with truss construction. Three sizeup indicators that the building has a truss roof are the absence of columns in a large space, a mounded roof surface created by a top chord of a bowstring truss and knowledge that certain occupancies, such as theaters, bowling alleys, supermarkets, garages, auto showrooms, skating rinks, piers and places of worship use truss construction. All these occupancies require a large space without columns.

chapter image Fig. 6.4  Two Valley Stream, New York, Firefighters, John Tate and Michael Moran, were killed when this place of worship “inclined plane,” gable truss roof collapsed.

A place of worship does not have the telltale truss indicator of the mounded roof and Firefighters may not realize it is a truss roof. The place of worship truss is usually an inclined plane configuration, creating what looks like a typical rafter peaked roof. So, the shape of the roof does not warn Firefighters of the danger. However, the occupancy should.

There was a peaked roof on a Valley Stream, New York, synagogue, the Temple Gates of Zion, where the local fire company stretched the first line to a room off the altar and quickly extinguished a fire. After the heat subsided at floor level, Firefighters were sent out to replenish masks when, suddenly, the truss roof crashed down and trapped Firefighters. What they could not see in the remaining smoke of the fire was a small spiral stair leading up to an attic space containing timber trusses. Fire had spread up to the attic and caused the timber truss roof to collapse, killing two Firefighters, John Tate and Michael Moran.

A lightweight wood truss roof collapse caused three Firefighter fatalities in Lake Worth, Texas, at the Precious Faith Temple church fire. While extinguishing a fire at the rear of the church at floor level, several lightweight wood trusses crashed through the ceiling, killing three Firefighters, Brian Collins, Phillip Dean and Gary Sanders. The truss is a dangerous roof structure and all places of worship should be assumed to have a truss roof. There is a saying in the fire service, “Beware the truss.”

Rose windows

chapter image Fig. 6.5  Venting these windows will not release smoke accumulated at the upper ceiling levels because of their low position in the wall. If the roof collapses, it can push out the side walls.

A rose window describes a large, circular, stained-glass window on the façade of a place of worship over the main entrance doorway. These high rose windows were designed to provide sunlight, high up, near the ceiling interior of a place of worship. This window is an important opening for firefighting. A rose window gives clear access to the upper reaches of a place of worship ceiling area where fire and heat accumulate. It can be used in a defensive attack on a fire, when Firefighters direct an aerial master stream through this window. An aerial stream delivered through a rose window can quench fire at the ceiling level that interior hose streams cannot reach. A 100-foot reach of an aerial master stream directed into a broken section of a rose window at a 30- or 45-degree angle sometimes can extinguish all the fire spreading at upper reaches of a place of worship that a hose stream cannot.

Window venting

In addition to a rose window at the front wall of a place of worship, there are also stained-glass windows on the side walls of a place of worship, but these windows are not as high as a rose window and do not assist firefighting as much. Venting these windows will not release smoke accumulated at the upper ceiling levels because of their low position in the wall.

There will be a higher, concave ceiling space inside above the height of the window top. A gothic ceiling or dome ceiling of a place of worship usually extends higher than the top of side stained-glass openings. These windows do not have to be vented when smoke inside a church is not a problem because it rises and accumulates above floor level. However, on arrival, if smoke and heat are banked down to the floor in a place of worship with a high ceiling, an interior operation should not be attempted. Fortunately, during early interior operations, smoke is not banked down to the floor where it obscures vision.

chapter image Fig. 6.6  In 2004, this bell tower of the Ebenezer Baptist Church collapsed and killed two and injured 29 Pittsburgh, Pennsylvania.

There is one scenario that dictates venting a side stained-glass window and that is when it would provide cross ventilation to the large interior space. Portable fans could assist cross venting without damage to the windows. Firefighters must use caution venting in a place of worship because it could feed the fire and cause a flashover or backdraft explosion. An IC should consider a fire in a place of worship to be similar to a high-rise office building fire; a cellar fire without venting.



The side walls of a place of worship support the truss roof structure. The walls and roof are connected. The side walls are bearing walls, supporting a load other than its own weight and can collapse when the roof fails. A collapsing roof will push out one or both of the supporting walls. The 1999 Lake Worth, Texas, Precious Faith Temple church fire that killed three Firefighters when the roof collapsed also caused one of the bearing walls to collapse out onto the sidewalk. Aerial photos show a large section of cinder block wall was pushed out in a 90-degree angle.

Wall collapse danger is recognized by church builders because the side walls often are reinforced with buttress structures. A buttress is a wall column built into the exterior of a wall to help it resist the side thrust of the roof. Incident Commanders must be prepared for a secondary wall collapse when fire is in control of the roof. Set up collapse zones and withdraw Firefighters a distance away from side walls equal to one, one and a half or twice the height of the wall.

Bell towers

Bell towers are the most unstable portion of a place of worship. A bell tower is less stable than the steeple because the bell tower may be an open stone structure with an interior wooden stair and ladder. This stair can have wood intermediate platforms and tons of movable bells at the top. Bells and bell towers at places of worship no longer are used and so they are neglected, not maintained and vulnerable to corrosion, foundation cracks and wind stress. Fire can spread up the interior of a bell tower, weaken the structure and any shock--such as an explosion or collapse--can trigger a bell movement and tower collapse.

In 2004, the bell tower of the Ebenezer Baptist Church collapsed and killed two and injured 29 Pittsburgh, Pennsylvania, Firefighters. A Firefighter who survived the Ebenezer Baptist Church collapse said, “Beware of the house of worship stone veneer.” Stone veneer makes a structure appear to be constructed of something other than what it is. This church had a false appearance of solid limestone blocks, measuring one by three feet. This was only a façade and gave a false sense of security to the structure. “We were under the impression the building was a lot stronger than it was and there was no way it could collapse.” Behind a stone veneer could be a lath and plaster concealed space.

chapter image Fig. 6.7  Two Quebec, Canada, Firefighters were killed when the collapsing roof pushed the wall out on them.

Regardless how the church walls appear, if the interior attack is successful and the fire extinguished by the interior attack hose teams, Firefighters immediately should attempt to open up the walls and ceilings near the smoldering fire. They may have concealed spaces. Check the concealed spaces for fire. If fire spreads to the concealed spaces, it may spread up to the large attic space. Flames may spread to an attic through the hidden voids behind the side walls, hollow imitation stone columns and through small holes in the ceiling level around chandelier lights.

In addition to opening up the concealed spaces after a fire is extinguished, Firefighters should quickly gain access to the attic space and check to see if fire already has spread to the large concealed space. Finding the stair that leads up to the attic may take some time and climbing the narrow spiral stair also may slow the Firefighters. However, this is an important action. If the fire is in the attic, the ceiling could collapse or the truss roof beams also could fall and trap Firefighters below. If fire is allowed to spread in the attic unnoticed, there could be a collapse on Firefighters performing salvage, washing down burned content and overhauling.


Structural engineers have identified church or temple towers and steeples as unstable features of a structure during an earthquake. The tower is the square structure rising above the church roof; the steeple is a pointed structure. There may be one or both on the front wall of a church. Sometimes, there is a pointed steeple constructed on top of a tower. A steeple tip has the cross on top. On a temple or mosque, the tower may have a domed, pointed sphere at its top. When the steeple or a tower is located at the front of a structure, this exposure “A” wall must be considered a collapse danger hazard.

The roof of a church with a peak roof is supported by the side walls. Side walls are running parallel with the peak ridge and are the bearing walls. A bearing wall is a wall supporting a weight other than its own. In a church, the weight supported by the walls is the roof.

These side bearing walls also are called primary structural members. A primary structural member supports another structural member. What does all this mean to an IC? It means if the roof burns and starts to collapse, it could push out the side walls. Conversely, if a wall fails, the roof would lose its support and collapse into the church or temple floor. Because of the church steeple and the interconnection of roof and side bearing walls, the exposure “A,” “B” and “D” sides of a burning place of worship are the most dangerous areas during a fire.



If the fire spreads to the attic of the church, there is plenty to burn. In an attic of a place of worship that has a gothic plaster ceiling beneath a peaked roof—such as Saint Patrick’s Cathedral, New York City--there are tons of wood. In the attic, there are two-foot-thick timber truss beams. There is the plank wood underside of the roof deck. There, a wood lath covering is bent to the shape of the plaster Gothic arch ceiling below. There is a wooden walkway from the back to the front of the attic space.

If fire reaches the attic spaces of most places of worship, it cannot be extinguished with handheld hose-lines. Access to the attic space is through one small door and there is no possibility to vent. Firefighters will have to be withdrawn and a defensive attack using a master stream strategy.

Before the roof collapses, the ceiling may collapse. If a large part of the ceiling collapses, it will create an explosion-like eruption inside the church that will blow out windows and knock Firefighters off ladders. As a large church ceiling collapses, it causes a compression below the falling ceiling of super-heated air, smoke and flame inside the church. This compression can blast out windows. The collapsing ceiling also will create a vacuum above the ceiling. This instant vacuum sucks air into the nowopen, attic space, creating a flashover of super-heated smoke and fire gases that had accumulated in the attic before the collapse.

A holy place

An added danger of fighting a fire in a place of worship is the emotional factor. Many Firefighters are religious churchgoers and some Firefighters at the scene even may attend the place of worship that is burning. When a church or temple burns, this usually attracts the local parishioners and they are watching their holy place of worship being destroyed by fire.

Inside the burning house of worship there are sacred books, scrolls, gold and silver tabernacles and objects containing their god. All this sometimes leads ICs, Sector Officers, Fire Officers and Firefighters to take unusual risks that might not be taken at an ordinary public residence or commercial building fire.

Again, even at a fire in a place of worship, the priorities of firefighting must be adhered to. The first priority is the life hazard that includes the Firefighters and the second priority is incident stabilization. Property protection is the last priority, even in a place of worship.

A place of worship battle plan

Despite the obstacles presented by the place of worship no-win battlespace, the initial battle plan of action is an offensive interior attack. Get in, knock the fire down quickly or get out! The strategy is to quench fire while it is small, before it reaches the ceiling and out of hose stream range, it grows to a size beyond cooling with hose streams or smoke prevents a quick size-up. First-arriving Firefighters should stretch a 2½-inch-diameter hose-line delivering 250 gallons per minute--one ton--and blast the fire. Other Firefighters should stretch a backup line and if you do not immediately extinguish the fire, withdraw.

chapter image Fig. 6.8  Despite the obstacles presented by the place of worship no-win battlespace, the initial battle plan of action is an offensive interior attack. Get in, knock the fire down quickly or get out!
  1. The initial attack hose-line is taken in a front or side door and attacks the seat of the fire. This hose-line must be the largest diameter hose available. Maneuverability of hose is not a factor. Large amounts of water and high-pressure stream with maximum reach are the necessary hose-line requirements.
  2. The second hose-line must be taken into the place of worship to back up the first attack hose team. This second or backup line may be needed to assist the first line in extinguishing a large body of fire. A large fire often is discovered on arrival in a church or synagogue fire because of a delay in discovering and reporting the fire.

  3. A portable ladder may be placed at the upwind side of a stained-glass window near the fire. A Firefighter climbing this ladder may vent the window with a pike pole. A portable ladder may be placed at the window on the opposite side of the building and create cross ventilation. However, Firefighters must know the top of a stained-glass side window will not remove smoke from the upper ceiling portions of a place of worship. In fact, it can add fresh air to a ceiling fire out of the reach of interior hose-lines. Venting stained-glass side windows is similar to venting the bottom portion of residence building windows.
  4. At a serious fire, consider venting the rose window at the front of the building. This opening can vent fire gases at the upper reaches of the place of worship.  
  5. The first aerial ladder at a serious fire should be positioned in a corner safe area at the front of the place of worship, out of a collapse danger zone and so Firefighters in the bucket can vent the rose window and, if necessary, direct an aerial master stream through it to extinguish flame at the upper reaches of the high ceiling. This action should be started only after all Firefighters have been withdrawn from the interior of the burning building. When a defensive strategy is used, aerial ladder master streams should be positioned on both flanks of a burning place of assembly, out of the collapse zone. There can be no defensive firefighting taking place inside a place of worship. The strategy is to start with an offensive strategy and if that fails, switch to a defensive attack outside the building. Never use both an interior and exterior firefighting operation simultaneously. It is interior or exterior; never both.

The game-changer

The game-changer is fire spreading to an attic, bell tower or steeple in a place of worship. If a Fire Officer cannot see the ceiling of a place of worship because it is filled with smoke and heat, a defensive outside attack should be considered because fire is growing up there and penetrating the ceiling going to the attic. If the IC receives a report fire has spread to the attic, bell tower or church steeple, Firefighters should be withdrawn and aerial devices moved into position and operated out of the collapse danger zone.

Place of Worship Battlespace Casualties

Pittsburgh, Pennsylvania, Chief and Firefighter killed and 29 injured when bell tower collapses. NIOSH 2004-17

Glossary of Terms

  • Apse: Part of the church that is a semicircle or U-shaped wall
  • Buttress: Masonry built against a wall to give additional support
  • Chancel: A space reserved for clergy, it includes altar and front choir area.
  • Nave: A main seating area of a church (assembly seating area)
  • Rose Window: A large, round, stained-glass window at the front of a Gothic church
  • Triforium: A middle story of a church (side balconies)
  • Transept: A space that runs at a right angle to the nave and chancel
  • Dome: A hemispherical roof on a circle tower or base
  • Gothic: Church architecture of 12th century and features a pointed arch

Chapter 7: Lightweight Truss Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Your home looks just like a lightweight truss construction battlespace. The territory appears like a non-threatening residence, but behind every wall and floor, there is a deadly enemy--the lightweight truss with the sheet metal surface fastener. The lightweight truss battleground also can be hidden in your local store or your new place of worship.

Lightweight truss roof and floor construction is everywhere and increasing. This battlespace has killed 22 Firefighters since 1984 and recent fire service efforts to make it less threatening have failed. The latest setback occurred in April 2016 when the fire service supported some insurance companies and the society of civil engineers who proposed better ways of nailing roofs together. The National Association of Homebuilders disapproved the proposal as too costly. This change to roof construction could have made roofs of new homes less likely to blow off during a hurricane and less likely to collapse during a fire.

This nation’s biggest battle involving burning buildings constructed with lightweight wood trusses occurred on January 22, 2015, at 4:30 p.m., when a plumber’s torch started a conflagration in a wall of an apartment in Edgewater, New Jersey. The fire service was badly defeated in this seven-hour battle. When the flames destroyed 240 residential units, it made 520 people homeless. This humiliating defeat occurred when winds blowing from the Hudson River rapidly spread flames to 240 luxury condos, necessitating 500 Firefighters responding from 35 mutual-aid municipalities, including fireboats from New York City and Jersey City to battle the blaze. The Fire Chief stated that fire spread rapidly in these buildings that were constructed with lightweight wood trusses, even though they were fully protected by automatic sprinklers.

chapter image Fig. 7.1  This nation’s biggest battle involving lightweight wood trusses occurred in an Edgewater, New Jersey, conflagration where 240 lightweight truss residential units were destroyed by fire and 500 people relocated.

Unfortunately, sprinklers are designed to extinguish fire in the living spaces; not in the concealed spaces where the trusses are located. This fire spread in the truss structure voids and crevices among the truss web members. The extinguishing system was not designed to stop flames spreading inside walls, floors, ceilings and attic spaces, as this one did. Fire officials explained flames will spread more rapidly in lightweight wood truss buildings than conventional, solid, wood-frame buildings or concrete and steel buildings.

This fire was our nation’s largest fire in buildings constructed with lightweight wood truss construction. It will be classified a “large-loss” fire by the National Fire Protection Association (NFPA); that is, a blaze destroying $10 million or more of property.

In 2013, there were only 21 large-loss fires. The Edgewater lightweight wood truss building fire also could be classified a “group fire,” one that destroys a large number of structures, but is confined within boundaries, such as an industrial complex or, in this instance, an apartment complex. This fire was confined by the Hudson River on the east and the Palisades Cliffs on the west and some dedicated Firefighters on each flank. Otherwise, it would have been a full blown “conflagration,” a fire that spreads beyond any natural or man-made boundaries.


In the 19th century, an east coast conflagration most often was in several blocks of old warehouses and factories built close together in a downtown area of a city. Today, in New York and New Jersey, a conflagration most often is a coastal pine barren wildfire that burns several thousand acres of woodlands and any homes built into this forest-like environment.

The NFPA states recurring causes of conflagrations are high winds more than 30 mph, wood shingle roofs, closely grouped buildings and poorly managed forests and woodlands. Perhaps after the Edgewater, New Jersey, fire, the NFPA may add lightweight wood truss construction as a recurring cause of conflagrations.

Concealed spaces and voids

A Fire Officer must know about lightweight truss construction fire spread vulnerabilities. After a serious fire in new construction, the Fire Chief is heard saying more and more often, the flames spread much faster in buildings constructed with lightweight truss construction. This fact often gets overlooked because the collapse danger takes the spotlight with lightweight truss construction.

The nation saw the horrific roof collapse that sent Fresno Fire Captain Peter Dern to the burn center. We pray for his recovery. However, when you investigate in-depth fire spread in lightweight constructed buildings, you see most fires in residence buildings start in the living spaces of a house, such as food burning on a stove or cigarettes igniting stuffed chairs, mattresses and wastepaper baskets of trash. These fires are easily extinguished by Firefighters using the same tactics as in any other construction type. Furnishings are the first item to burn in a residence fire and if not extinguished quickly, flames can spread to the concealed spaces through the walls, ceiling and attic void spaces and feed on the infrastructure.

chapter image Fig. 7.2  Fire travels in two directions simultaneously: parallel direction between the truss beams and perpendicularly through the truss web members.

Fire travels in two directions simultaneously: parallel direction between the truss beams and perpendicularly through the truss web members.

An infrastructure fire in a building of lightweight wood, not a content fire, is the fast-spreading blaze the Fire Chief is talking about. An infrastructure fire in concealed spaces speeds more rapidly in truss construction than ordinary, solid-wood construction.

For example, in an ordinary traditional residence building, if flames enter the voids, it travels in one direction between the joists. This construction partially constrained concealed space fire is extinguished easily when Firefighters open the ceiling and use a hose stream into the ceiling space. However, if fire burns inside a truss-constructed concealed space, it travels in two directions simultaneously:

  1. Parallel direction between the truss beams and
  2. Perpendicular direction through the truss web members.

A Fire Officer must know that when opening up ceilings and floors searching for concealed fire spread inside a truss structure, it is almost impossible to stop this two-direction spread. The old tactic for solid-beam construction fire cutoff will not be successful. For solid beams, if fire is detected between floor beams with a thermal imaging camera, go to the nearby wall, open it up and cut flame spread off at this point and work back. If fire is discovered in a wall, pull the ceiling above the hot wall, cut it off there and work back. If fire is discovered in a ceiling, go to the floor directly above and open it there. This tactic will not be successful in a truss building because fire spreads rapidly in two directions.

Mass and fire resistance

Another factor in fire spread in truss-constructed buildings is reduced structure mass. Fire resistance is directly related to the mass of a structure; the more mass, the more fire resistance. Lightweight construction is constructed of small pieces of wood. The largest is two by four inches in diameter and has been called a house of sticks. Lightweight wood truss buildings have less mass than the older post and girt construction or even platform construction using solid beams. In conventional wood construction, there are timbers and two- by eight- or by 10-inch solid beams.

A lightweight truss structure also has what engineers call a high “surface to mass” ratio. Lightweight trusses have a high surface area and so it can burn quickly. On the other hand, a structure with a low surface to mass ratio is constructed with large pieces of wood, such as heavy timber, which is more difficult to ignite and takes longer to burn.

For example, a large timber is difficult to ignite with a blow torch, but if you cut the timber into small toothpick sizes of wood, you greatly increase the timber’s surface area and this pile of toothpicks will ignite more easily and burn more rapidly. The reason Fire Chiefs declare the fire spreads too rapidly in truss construction and cannot be contained by hose streams is these buildings have less mass and higher surface to mass ratio.


Truss building identification

A Fire Officer must know how to identify a lightweight truss building during a size-up to prepare for a fire that will spread rapidly. The best way to know if a burning building is lightweight constructed is to visit the construction site while it is being built. Fire Officers should visit every construction site to examine in detail each new material used.

Building construction is changing rapidly--solid beam truss, “C”-shaped steel beams, wood I-beams, steel bar joists--can be used in residence construction and all of this new construction will have a various degree of fire spread. Lightweight truss construction is the most popular new construction.

Some telltale signs of truss construction are:

  1. The angle of the roof slope is often the same 30-degree, low slope roof.
  2. Instead of a window at the gable ends of a roof, there will be a vent louvre opening.
  3. In some instances, a quick glance into a garage can identify the roof construction of the main building.

The key to effective firefighting and safety from collapse at any fire involving truss construction is early identification of the truss and immediate reporting to the IC. Firefighters and Officers must report the presence of truss construction to the Command Post. Only when informed of the truss construction can the IC order effective firefighting strategy to stop a fast-moving flame spread.

Truss construction building indicators

There is a trend in the fire service of requesting laws to be passed marking buildings with truss construction with warning signs. Hackensack, New Jersey, has truss buildings marked with a triangle; Chesapeake, Virginia, requires truss buildings to have a letter T; and New York State has two vertical lines to identify truss construction. However, these laws usually only apply for commercial buildings.

This does not help because residence truss buildings are where the rapid fire spread is being discovered and where Firefighters are killed. The fire service cannot depend on size-up or laws to give us information about this fast-burning construction; we must take action.

To do this effectively, the individual fire company must identify truss buildings in the community when they are being built and this information must be programmed into the dispatch systems. When an alarm is received, dispatchers notify fire responders of the truss construction information programmed into the computer by radio. Fire Officers must have this information before they arrive at the scene to stop rapid fire spread. In addition to identification and reporting the truss, the fire service must develop standard operating procedures (SOPs) to combat the rapid spread of fire associated with this construction.

Passive fire protection

Not so long ago, traditional wood residence buildings had passive fire protection built into the structure when using wood materials. The construction features would assist Firefighters stopping fire spread in concealed spaces. Passive fire protection is fire resistance by construction. Some examples of passive fire protection in traditional construction that are not present in truss construction are:

chapter image Fig. 7.3  This house of sticks has nothing larger than two-by-four wood members.
  1. Solid, full-depth bridging was used every eight feet to stiffen and brace a floor system. A two-by 10-inch floor beam would have a solid-wood, two-by-10 block nailed between the joists. This was designed to enhance the stability of the floor structure, but also was an indirect fire-stop for flame that spread into the concealed floor spaces.
  2. Wall stud bracing sometimes was used in a stud wall halfway between the bottom of the wall and the partition top. This solid block of wood fit horizontally into the concealed wall space, also indirectly providing a fire-stop for flames that burned through the plaster wall, spreading vertically in the space between studs.

  3. Brick nogging used as insulation and soundproofing between attached wood buildings and the bricks placed in the vacant spaces of wood wall also acted as a fire barrier, slowing down fire spreading from one building to another or room to room.
  4. Even as stated above, solid wood floor and roof beams would channel flames between the joist so it would spread only in one direction and Firefighters had a chance to open a ceiling and shoot a hose stream into the concealed space and extinguish the fire.

Truss construction has none of the above passive fire-resistive construction techniques that assisted Firefighters for centuries. In fact, the truss open web spaces and small dimension wood speed up fire spread in concealed spaces.

Stopping fire spread with automatic sprinkler systems

The Edgewater, New Jersey, fire on January 20, 2015, occurred in four-story, lightweight wood truss buildings that had the interior of the buildings fully protected by automatic sprinklers, but this system had no effect on the fire spreading in the walls, ceilings and attic spaces. These luxury apartments housed more than 500 people who lost everything as their homes were totally destroyed by fire.


To improve effectiveness of automatic sprinklers, they must be installed in the concealed spaces, ceilings and attics, in addition to the living spaces. The sprinklers in

Edgewater, New Jersey, were designed only to extinguish a furnishing or content fire occurring in the living spaces, not a fire in concealed spaces. Sprinklers would be more effective in the concealed spaces of lightweight truss-constructed buildings because this is where the fire spreads most quickly and where Firefighters have most difficulty extinguishing flame with hose streams. Firefighters are trained to extinguish furnishing fires and are effective at doing this. They have no problem extinguishing a fire in the content of a lightweight truss building; it is when a fire spreads to the concealed spaces and spreads uncontrollably in the truss spaces that Firefighters are defeated. This area requires automatic sprinkler protection.

Stopping fire spread with hose-lines

With any fire, the most important action is the operation of the first attack hose-line. Stretch the first line to the fire origin and extinguish the flames, then order a second, backup line to protect Firefighters with the first line in case there is an explosion, flashover or too much fire. And in a multi-story building, stretch a third line to the floor above to prevent vertical fire extension. This is the strategy for most fire in wood residence buildings.

However, Fire Officers, including myself, advise a different strategy for fire in buildings constructed with lightweight truss construction. This strategy recommends the following:

chapter image Fig. 7.4  This HVAC machine is placed directly on the lightweight truss roof.
  1. Stretch the first line the same way into the interior and extinguish the content fire. If the fire involves only the furnishings, such as a stuffed chair, couch or mattress, we use our standard interior attack. As soon as the fire is extinguished, Firefighters must examine concealed spaces. They open the ceilings above the quenched fire and open up nearby walls, checking for fire spread to the concealed spaces. If fire has not spread to the concealed spaces, this successful strategy has the same standard operating procedures for any solid-beam traditional construction fire.
  2. However, if when the Officer orders Firefighters to open up a ceiling or wall and flames are discovered spreading uncontrollably in the concealed spaces with lightweight truss construction, notify the Incident Commander. The IC should not order a standard attack of a second or third line and instead all occupants should be removed and the fire extinguished from the exterior. This fire in the concealed spaces will spread too rapidly throughout the truss infrastructure for an interior defensive strategy to be effective. Fire spreads rapidly in the concealed spaces and the truss structure quickly becomes a collapse danger.


The building industry has constructed more affordable housing for Americans and increased revenues by using this fast-burning construction with lightweight trusses and will not change, so the fire service must change its firefighting strategy.

Structure collapse

The nation recently saw a video showing Fire Captain Peter Dern, of the Fresno City Fire Department, critically injured by a roof collapse. This roof was lightweight truss construction. Captain Dern’s name would have been added to the list of truss roof collapse Firefighter fatalities at the end of this article if it weren’t for the fast actions of a Rapid Intervention Team (RIT).

The following are six construction features that contribute to early collapse of lightweight truss roofs at fires. They are the sheet metal surface connections; the absence of a standard size connection; truss failure before roof deck failure; no ridge rafter; the top and bottom chords are spliced and not continuous pieces of wood; and heavy air conditioning machinery (HVAC) overloads the lightweight truss construction.

chapter image Fig. 7.5  There is no standard size for connections; some are small, some are large.

The sheet metal surface fastener

This is a defective connection. As the name suggests, it only connects the surface of the wood truss sections. The piece of sheet metal does not penetrate the wood as does a nail or bolt. At a construction site, the sheet metal connections sometimes come apart during unloading and rough handling and there is a warning sign attached to the truss, stating the damaged connection should not be repaired or used. Yet, in some instances, the defective truss is used.

From a fire protection point of view, the sheet metal surface fastener is a sub-standard, dangerous connection and should be outlawed. When you investigate a lightweight truss collapse scene after a fire, you find it is not the truss that fails first, it is the sheet metal surface fasteners. They fall off the wood when it chars or they curl up and partially pull away from the wood surface when heated, leaving the truss section in place, but not connected. This thin surface fastener is a piece of sheet metal with punch-out points and only penetrates the wood surface ¼- to ½-inch in depth.

As the name suggests, it is a surface connector. It does not penetrate the wood and, as a result, it fails quickly. When exposed to flame, the wood truss chars, blackens and suffers what is called “alligatoring”--a surface of charred bumps and crevices. When “alligatoring” occurs, sheet metal connections fall away from the burned wood surfaces and leave the truss unconnected. As the thin sheet metal pieces heat and fall off charring wood surfaces during a fire, a serious collapse hazard begins. Firefighters working on a roof to cut a vent opening are in danger of the unconnected truss sections coming apart. Sometimes, the connections do not fall away; they curl up and pop off of truss sections and leave two or three sections of a truss unconnected and in danger of collapse.


There is no uniform, standard size, sheet metal connection

When a standard, solid-wood residence structure is to be built, carpenters will have a barrel filled with five- or 10-penny nails to be used to fasten the structure together or carpenter’s nail guns used by several carpenters will have similar sized nail fasteners loaded into the gun. All wood structure members used to have standard size nail fasteners for structural connections. Not so with lightweight trusses.

When examining truss floors and roof sections are laying around, Firefighters will see there will not be standard size connections connecting the wood pieces of truss together. The sheet metal connections of two or three sections of wood will vary in size. Some will be three by six inches, some will be two by four inches and others can be as small as one by three inches. When the connectors of a truss vary in size, so will the strength of the truss.

The rule of truss stability is the truss is only as strong as its weakest member. That will be the smallest sized sheet metal connector. The sheet metal fasteners are not melted by the heat of fire; they simply fall away from the wood because they do not deeply penetrate the wood. After a fire, sheet metal connections will litter the floor or roof space. Or, sometimes, they distort and pull away from one of the pieces of wood and partially stay in place. When sheet metal fasteners fail, a charred, unconnected truss remains in place by gravity. Any vibration, such as a Firefighter cutting with an ax or saw or removing the roof deck, suddenly can collapse a fire-weakened truss.

Roof deck is stronger

chapter image Fig. 7.6  The sheet metal surface fasteners are missing and the roof deck is not burned. Truss supports failed before the roof deck.

A parallel chord truss can fail before the roof deck. In some instances, the truss roof system comes apart before the wood deck fails. With most construction, the roof deck burns away first and the solid rafter system continues supporting the deck. No so with lightweight trusses. In this construction, the ¾- or oneinch plywood deck outlasts the trusses and sheet metal surface fasteners. Firefighting size-up experience has shown, up until use of truss construction, the roof deck fails before the supporting wood roof system below. This no longer is true with a lightweight wood truss system.

On page 109, the photograph of a roof vent cut shows a horizontal roof truss support system burned and charred and the missing sheet metal truss fasteners have fallen away, littering the fire room floor. Some were still in place, but half curled up on the truss, not connecting the intended two sections of the wood. Fortunately for the Firefighters who cut this vent opening, the truss did not collapse. The photo also shows the ½-inch plywood roof deck still intact, providing the only roof stability. A lesson learned with this photo is a thin plywood deck is the last line of defense on a truss roof and if a roof deck fails, there is nothing to stop a Firefighter from falling into the fire below. This photo reveals how a lightweight truss roof differs from a solid-beam roof in a fire.

Fire experience has shown a roof deck is the first part of the roof to fail and even after this, solid roof beams below the deck continue to support the roof. If the roof deck collapses, a Firefighter can grab onto the solid beams below to keep from falling into the fire. Not so with truss construction.

There is no structural ridge rafter at the peak of a truss roof

On solid rafter sloping roofs, there is often a structural ridge rafter at the peak, which supports roof rafters. The structure ridge rafter and the bearing walls independently support roof beams on each side of the sloping roof.

A lightweight truss peaked roof will not have a structural ridge rafter at the peak; if one side of a truss fails, the other side does, too. Firefighter size-up experience may assume there will be a structural ridge rafter at the peak, roof rafters on each side of the slope will be independently supported and this construction could provide safety for Firefighters after they cut a vent opening on one side of a peaked roof.

For example, after performing a vent cut, if they crossed over the peak on the opposite slope, they were independently supported. Here, the high end of the roof rafters were supported by the ridge rafter and the low end supported by the bearing wall. This safety maneuver no longer is possible on a truss roof because there is no structural ridge rafter. The fire-weakened truss rafter on one side can cause the collapse of its other sloping side.

With a lightweight truss sloping peaked roof and no structural ridge rafter and one side of the sloping roof fails, the other side fails, too. The 1989 Phoenix, Arizona, truss roof video reveals this danger. It shows two Firefighters falling though a fire-weakened roof on one side of a peaked roof and a Firefighter going to their rescue and falling through the roof on the other side of the sloping gable roof.


Truss chords are spliced together

Top and bottom chords of lightweight wood trusses are not on long pieces of wood. Instead, they are several smaller sections spliced together with the same ineffective sheet metal fasteners. The top and bottom sections of a truss, called chords, usually are one piece and larger sized than the web members, which are smaller pieces of wood in the middle of the chords, holding the truss together. In a timber truss, top and bottom chords will be one continuous section of laminated wood and also larger sized wood than the smaller, intermediate web members.

Chords of lightweight wood trusses are not continuous beams and they are not even larger pieces of wood. They are the same size as web members, but more dangerous, because they are spliced into one long section with sheet metal fasteners, penetrating only the surface of the wood. The chords are not providing any more strength to the truss than smaller web members.

Heating, venting and air-conditioning machinery (HVAC) overloads a truss

A heavy air conditioner should not be resting directly on lightweight truss roofs or hanging from a truss in an attic dormer. HVAC roof machinery should be independently supported by steel beams that transfer its weight to adjacent bearing walls from there to the foundation. Lightweight truss roof construction cannot support heavy roof loads and will collapse at this point during a fire.

Current unsafe construction methods allow HVAC machinery to be placed directly on the truss roof. The only reinforcement required is to double up the lightweight truss sections. This is totally unsatisfactory.

There have been two fires where four Firefighters have been killed because heavy HVAC machinery supported by roof trusses collapsed during fires. During a fire in a gift shop in Orange County, Florida, roof trusses supporting an HVAC machine collapsed and trapped and killed Firefighters Todd Aldridge and Mark Benge. In Houston, Texas, a fire in a McDonald’s fast food restaurant with HVAC machinery supported by the roof, collapsed during a fire and killed Firefighters Lewis Mayo and Kimberly Smith.

If an inspection of commercial fast food restaurants in your community reveals heavy HVAC machinery placed directly on the roof supported without reinforcement, it should be referred to the Building Department. If the local Building Department approves this construction over your objections, an alternative defensive firefighting strategy should be drawn up and used at fires in the occupancy.

The following tragic list of Firefighter fatalities illustrates the dangers of lightweight wood truss collapse. The National Institute of Standards and Technology (NIST) and National Institute of Occupational Safety and Health (NIOSH) and independent research have identified the following lightweight truss collapse incidents that have killed Firefighters in the past 30 years:

  • James Presnall, Irving, Texas, 1984, caught and trapped below a roof collapse, fighting fire in a building under construction.
  • Todd Aldridge and Mark Benge, Orange County, Florida, 1988, caught and trapped below the collapsing roof of a gift store that was supporting a heavy air conditioner in the dormer.
  • Alan Michelson, Gillette, Wyoming, 1990, fell into the fire area when the roof of a church collapsed.  
  • James Hill and Joseph Boswell, Memphis, Tennessee, 1993, caught and trapped below a church roof collapse.
  • Strawn Nutter, Louisville, Kentucky, 1994, fell into the fire area when the roof of a self-storage building collapsed.
  • John Hudgins and Frank Young, Chesapeake, Virginia, 1996, caught and trapped below an auto parts store roof collapse.
  • Edward Ramos, Branford, Connecticut, 1996, caught and trapped below a roof collapse of a carpet store.
  • Brant Chesney, Forsythe County, Georgia, 1996, fell into a cellar when a floor of a house collapsed.
  • Garry Sanders, Phillip Dean and Brian Collins, Lake Worth, Texas, 1999, caught and trapped below a church roof collapse.
  • Lewis Mayo and Kimberly Smith, Houston, Texas, 2000, caught and trapped below a collapse of a fast food restaurant roof supporting heavy air-conditioning machinery.
  • John Ginocchetti and Timothy Lynch, Manlius, New York, 2002, fell into a cellar when a floor of a residence building collapsed.  
  • Cyril Fyfe and Kevin Olson, Yellowknife, Canada, 2005, caught and trapped below the collapsing roof of a lumberyard shed.
  • Arnie Wolfe, Green Bay, Wisconsin, 2006, fell into a cellar when a floor of a residence building collapsed.
  • Scott Davis, Muncie, Indiana, 2011, caught and trapped beneath a church roof collapse.
chapter image Fig. 7.7   Most Firefighters killed by lightweight truss roofs are killed inside the building when the roof collapses on top of them. Firefighters Todd Aldridge and Mark Benge were killed in this lightweight truss roof collapse in 1988.

The above list details 22 Firefighters killed fighting fire in lightweight truss construction buildings; 16 of them killed inside burning buildings by truss roof collapse, four Firefighters killed falling through truss floors and two Firefighters killed falling through truss roofs.

Recent scientific, full-scale testing by Underwriters Laboratories (UL) in 2014, titled Improving Fire Safety by Understanding Fire Performance of Engineered Floor Systems, has documented once again the early collapse danger of lightweight construction. An important finding in this study was comparing failure time of lightweight truss construction to other joist systems. The following are documented failure times of several floor systems:

  Floor System   Avg. Failure Time (min.)
Solid-wood beam 15:01
Wood I-joist 7:20
Steel C-beam 8:10
Lightweight wood truss 4:48

The above results of the UL 2014 fully scaled fire tests were designed for floor joist systems. However, the fire service can assume similar collapse results for roofs.

Fire and wind

“Dogs may bark, but the caravan moves on.” The dogs in this case are the fire service, insurance companies and engineers at a National Association of Homebuilders conference on April 16, 2016, in Louisville, Kentucky, who proposed better ways of fastening roofs together that would keep them from blowing off during hurricanes and collapsing during fire. The caravan drivers were the lobbyists and bureaucrats of the National Association of Homebuilders who disapproved the proposals as too costly.

This change to roof construction could have changed residential building codes, making roofs of new homes less likely to blow off the house during a hurricane or tornado and collapse during a fire. Nails! Nails! Nails! Nails! We want nails! The insurance companies and engineers want more of them in roof construction to make them stronger during storms. This debate was mainly between the insurance companies and engineers versus the homebuilders, but the fire service was watching closely.

The insurance and engineering community wants to prevent roofs from sailing away during high winds and the fire service wants roofs and floors less collapse-prone by using more and bigger nails, not flimsy sheet metal surface fasteners and glued joints as they are today. The battle at this meeting was really fought by the insurance industry and engineers. However, the fire service has “skin in the game” because roofs that easily blow off also easily collapse during fire. The fire service supports this battle for stronger roof construction.

chapter image Fig. 7.8  This would not have happened if there was a ridge rafter in the roof construction.

If builders or home owners really want to harden roofs from fire or hurricanes, we know how to do it. Let us start once again by building roofs that have heavy, solid rafters, not lightweight pieces of truss wood. Also, let’s return the ridge beam to the roofs to connect the tops of rafters together and return the collar beams in the attic, stiffening opposing roof rafters and, finally, let’s have the roof rafters nailed, not just fastened on the surface or glued at joints.

Today, the affordable lightweight truss roof beams can be connected only on the surface without the use of penetrating nails. The fire service wants nails, nails, nails, too! It took decades for builders and building codes to allow the “softening” of roof construction, taking away mass, substituting lightweight trusses for solid-wood roof rafters, removing the ridge rafter from the roof peak, omitting collar beams in the attic and replacing the number and size of nails used in roof connections. Trusses have replaced solid beams and they are fastened together with thin metal surface fasteners that do not penetrate the wood, but sink into the surface only ½-inch and sometimes they use glued joints for these trusses that replace solid-wood roof rafters.


All of this change has been to make houses more affordable. Yes, they are more affordable, but now the roofs blow off more easily during strong winds and the fire service also knows floors collapse during the early stages of fire, killing Firefighters. Now building and insurance companies want to “harden” the roof construction. Builders know how to harden these roofs to keep them from blowing off the structure, but it is expensive. For example, they can reinforce a roof to handle lateral forces acting along both the length and width of the peaked roof structure, as well as an uplift vertical force. A wind-resistant roof is dependent upon all of the roof’s structure combined, such as the rafters, ridge beam, collar beams and nailing of the entire roof to the supporting wall plates. Engineers know poor connections (lack of nails) are the single most common reason for failure during wind events and the fire service knows it is the single most common reason for burning building collapse, too.

Today, home owners incorrectly assume their roof will be built to a high standard if it complies with the building code. Builders like to brag everything will be up to code. This is a false assumption. Building codes are minimum standards. Some in the National Association of Homebuilders and the construction industry believe a home owner bears some responsibility of a home’s ability to resist high winds and collapse. And, they say a home owner should pay for any upgrade of roof construction. The insurance companies, architects and engineers recommend a home owner request this additional roof tightening if needed, but even if you do not require additional roof bracing, every home owner should ensure that the builder uses the required number of nails for all roof connections.

Roofs blow away by winds and they also collapse during fire. Since 1984, 22 Firefighters have been killed in buildings using lightweight truss roof and floor construction connected with flimsy sheet surface fasteners and glued joints, instead of solid wood connected with nails. So Firefighters have been warned about the roof and floor dangers of lightweight construction. Fire Chiefs who practice “risk management” strategy recommend if flames involve the structure parts of a nail-less lightweight truss building, Firefighters use more defensive tactics, consider early withdrawal of occupants and fight the fire from the outside.

Soft building construction

How did we get sheet metal fasteners and glued connections holding up floors and roofs? The “softening” of home building began after WW II when building codes in America changed from “specification” to “performance” codes. Today, all codes are performance codes. With a performance code, for example, you cannot specify the use of 10-penny nails or any other specific construction material. Very few specifications are used in a code today. As a result, there are several different kinds of connections--other than nails--used in home construction.

For example, there are sheet metal surface fasteners and the glued truss connectors that have passed a fire performance test and replaced the more expensive, but more effective, nails. As one pessimistic Firefighter stated, “If we ever invent a type of Velcro or tape that can pass a performance test, we will have taped or glued roof construction.” A home owner eventually will have to pay for any fire- and hurricane-resistant improvements, such as more nails, either way. It may be by requesting and paying a builder for extras as I did, from pass-along costs if the National Association of Homebuilders does agree to strengthen residential building codes or by higher insurance costs after fire or wind damages a roof.

A lightweight truss building battle plan:

Fire involves only furnishings and content; not the lightweight trusses.

  1. The first hose-line goes to the fire and extinguishes the flames, using a standard operating procedure.  
  2. Second line backs up the first line.
  3. Ground ladder used for rescue.
  4. Primary venting by placing ground ladder at window of fire room; Firefighter with pike pole vents window, coordinated with hose-line advance.
  5. Aerial ladder positioned for rescue and/or master stream use.

Fire involves the truss structure and cannot be extinguished with initial water stream.

  1. Second hose-line is large diameter, stretched into aerial ladder for master stream use.
  2. Ground ladder remains on truck.
  3. Primary venting: none.
  4. Aerial ladder uses master stream to protect exposures. All persons should be evacuated from the building and defensive outside hose-line attack used. There should be no roof venting operations. A collapse zone should be established at the perimeter of the burning building and nearby structures protected by hoselines.

The game-changer

The game-changer is a report from a Firefighter that the burning structure has lightweight truss construction. A report to Command of the presence of lightweight wood truss or wood I-beams should change the IC’s strategy. If the fire involves the truss structure, the strategy should be changed from interior to exterior attack. Fire experience and scientific tests document there is a five- to 10-minute period before collapse starts. Occupant evacuation, defensive outside attack and protecting exposures are recommended.

Another game-changer is a report of unsupported roof machinery—HVAC—resting directly on the roof. Firefighters must report heavy machinery supported on the roof of a building. Roof machinery is a contributing cause of lightweight truss collapse.

Lightweight Truss Battlespace Casualties

Houston, Texas, two Firefighters killed when fast food restaurant roof collapses NIOSH 2000-13

Chapter 8: High-Rise Building Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Helmuth von Moltke said, “When your plan meets the real world, the battle plan survives contact with the enemy,” German military strategist real world wins. Nothing goes as planned.” However, General Dwight

Eisenhower said, “Plans are useless, but planning is indispensable.” An Incident Commander (IC) must understand there is a difference between a plan and planning. With high-rise firefighting, you must have a plan, but you also must be ready to change or alter some parts of the plan when things go wrong. The following are 10 high-rise construction “plan disruptors” that can make an IC alter or modify a high-rise firefighting plan of action.

Fire resistance fails.

High-rise buildings are not fire-resistive. The National Institute for Standards and Technology (NIST) has declared a new definition for a fire-resistive high-rise building. NIST defines a high-rise building as one that will burn and not collapse. No mention of resisting fire; just “will not collapse.” This is a comedown on the safety of high-rise buildings.

In the 1950s, the National Fire Protection Association (NFPA) defined the term fire-resistance building as a building that barring an explosion or collapse, fire will not spread from one floor to another for a designated time--one, two or three hours. Fire can spread in a high-rise building on the inside and outside. Fire and deadly smoke can spread on the inside of a high-rise through the air conditioning system.

chapter image Fig. 8.1  This historic fire at One Meridian Plaza, Philadelphia, killed three Firefighters and spread to nine floors.

In the 1940s and ‘50s, buildings did not have air systems connecting five or 10 floors together with air ducts. Back then, heating, venting and air conditioning (HVAC) systems served only one floor. Today, the air ducts of a HVAC system penetrate all the walls, floors and ceilings of five, 10 or more floors in a building. And, sometimes, the safeguards built into a HVAC system do not work.

For example, at the MGM casino fire in Las Vegas in the 1980s, where 80 people died in hotel rooms, fire dampers in the ducts that penetrate walls or floors designed to stop smoke spread triggered by heat-sensing devices sometimes were set at higher temperatures than the smoke spreading in the ducts and did not close properly. And detectors intended to be installed inside return air ducts designed to shut a system down when smoke was detected were missing and/or defective. This allows interior spread throughout HVAC air ducts for several floors.

The outside walls of a high-rise building pose another fire protection problem. Flames can spread up the outer walls of a building that has been renovated by installing a new combustible aluminum cladding on its exterior walls. In some instances, a flammable plastic insulation or glue is used behind the metal cladding. This new combustible cladding-spread flame rapidly can rise up the exterior walls of a building and spread inside the structure through windows, air conditioners and poke-through holes in the exterior wall.


The fire at the United Kingdom Grenfell tower--a 24-story high-rise--on June 14, 2017, was a tragic example of a combustible cladding fire. The fuel that allowed fire spread and killed 71 people was plastic insulation installed between the old façade and the new aluminum cladding. It is recommended that a noncombustible, mineral wool fiber insulation be used instead of flammable plastic insulation.

We now can add combustible exterior cladding to the other outside avenues of fire spread in a high-rise building, such as auto-exposure--window to window--and the small space between the curtain wall and the outer edge of the concrete floor.

The National Institute of Standards and Technology (NIST) has told the fire service something we suspected for several decades

High-rise buildings no longer are fire-resistive. We in the fire service have seen fire spread on the inside and outside of high-rise buildings for decades.

For example, in New York City in 1970, the One New York Plaza high-rise office building fire spread two floors from the 33rd to the 34th floor. And in the 1980s, fire spread five floors in a Los Angeles high-rise, the First Interstate Bank building. In the 1990s, the One Meridian Plaza fire in Philadelphia spread nine floors, from the 22nd to the 30th floors. And in 2001, the uncontrollable fires that resulted from the terrorist attacks on the World Trade Center spread and caused the high-rise towers to collapse. These major high-rise fires showed the world and the fire service the vulnerability of modern high-rise building construction to fire spread on the inside and outside of the structures. So NIST has told us the truth, “the emperor has no clothes.”

Large, open floor areas are beyond reach of hose streams.

Firefighters cannot extinguish fires in today’s high-rise office large, open floor spaces. An office floor area in a 100- by 100-foot-wide building that does not have any interior partitions may help productivity of the workers, but if a fire spreads throughout the space, the Firefighters will be unable to extinguish such a large fire using hose streams.

chapter image Fig. 8.2  A 10,000-square-foot area floor cannot be extinguished with hose-lines. chapter image Fig. 8.3  Spray-on fire resistance is blown off by HVAC air movement.

A typical large office floor has a center core containing stairs, elevators, bathrooms and storage areas. Additionally, there is the ceiling and maybe small offices around the perimeter of the floor area, but most of the interior is one large area that if fire spreads in it, Firefighters will be unable to quench it because of the size. A 200- by 200-footwide building can have a 40,000-square-foot open floor area.

There is an informal, general rule in the fire protection field that says a space more than 5000 square feet should be protected with an automatic sprinkler system because it is too large for Firefighters to extinguish with handheld hose-line. The fire service cannot extinguish a fire in a 20- or 30-thousand-square-foot open floor area in a highrise building when it is full of heat, flame and blinding smoke. At best, Firefighters advancing a 2½-inch hose-line with a 1⅛-inch nozzle discharging 250 gallons per minute can extinguish only about 2,500 square feet of fire.

If the fire department has the resources to back it up with a second hose team, two hose-lines can extinguish perhaps 5,000 square feet of flame. One reason Firefighters cannot extinguish fire in large spaces is the reach of a hose stream. A water stream from a large, handheld hose directed from a doorway can reach only 50 feet inside the area, not 100 or 200 feet. A modern, open floor office design, with cubicle work stations and/or dwarf partitions separating areas on a floor can have flame and smoke spread quickly throughout a 100- by 200-foot floor area. City managers and some Fire Chiefs will not admit this to the public if they want to keep their jobs. However, fireground Commanders who work in high-rise office building areas know this is a fact.


What really happens at a high-rise office building fire in a large floor area is what we call “controlled burning.” That is, Firefighters are unable to advance in on the fire from the doorway, operating the hose stream in a stationary defensive position for as long as it takes for all the contents on the floor to be consumed by flames. If the ladders can reach, outside hose streams may add to the effort. But only after all the plastic desks, computers, paper, electric wiring and cable, ceilings and partitions are burned to a crisp by fire and heat subsides, can Firefighters then move in to extinguish the hot spots.

To effectively extinguish a high-rise fire, it takes 70 to 80 Firefighters using a rapid-response, blitz attack. If this fails, it will take another 100 to 200 additional Firefighters. Most fire departments do not have this capability, so city planners must ensure every high-rise office building is fully protected with an automatic sprinkler system and smoke detectors.

Spray-on, fire-retardant material (SFRM) is missing.

The fire-retarding material protecting structural steel from fire is ineffective. After 40 years of use, there is no scientific basis for how thick spray-on, fire-retarding material should be to give structural steel protection from fire for a specified time. The NIST investigation of the World Trade Center terror attack on 9/11 revealed there was no fire test documentation to determine the thickness of spray-on insulation to give steel a one-, two- or three-hour fire resistance. The thickness (½- to ¾-inch) of the (SFRM) spray-on first was applied to the structure steel to give it two hours of fire resistance. Then, after tests in the 1980s, the thickness of the WTC SFRM insulation was increased to 1½inch. At that time, the thickness of the 1½-inch fire-retardant spray-on was said to provide fire-retarding protection of the steel supporting the floors for two hours.

chapter image Fig. 8.4  Exterior insulation finish system (EIFS) used as exterior wall cladding on high-rise buildings, creating exterior fire spread, has become a major fire service concern.

Fig 8.4 Exterior insulation finish system (EIFS) used as exterior wall cladding on high-rise buildings, creating exterior fire spread, has become a major fire service concern.


During the 9/11 investigation, no fire testing documentation was found to justify ¾- or 1½-inch thickness of SFRM would provide a two-hour fire rating for steel floors. In addition to disagreement about the thickness of the fire-retardant spray-on, it was discovered that it falls off the steel due to air movement of the air conditioning and heating systems.

Adhesion to the steel, consistency of the fire retardant to cover all the exposed steel surfaces and correct thickness are the three criteria that NIST determines are necessary criteria for the spray-on, fire-retardant material effectiveness during a fire. To adhere to steel, the steel must be clean. In addition to incorrect thickness, it was discovered the spray-on mistakenly was applied to steel that first had been covered with primer paint. Tests at NIST laboratories showed when covered with primer paint, fire retardant had only one third to one half of the adhesive strength and fell away more quickly than if the steel was not painted.

This method of spray-on fire protection of steel was known to be ineffective since its introduction in the 1970s. And during the investigation by the NFPA or UL of every serious high-rise office building fire in America, a large area of steel and concrete composite floor cracked and floors sagged or heaved up and had to be replaced after the fire. NIST determined the cause of this floor damage was spray-on fire retardant missing from structural steel girders and beams.

chapter image Fig. 8.5  Firefighters must take the elevator two or more floors below the fire floor.

Elevators stop working.

Elevators fail during high-rise fires. Elevators in highrise buildings are perilous and unpredictable during fire. Occupants and Firefighters using elevators can be trapped in a smoke-filled hoist way, taken above an uncontrolled fire or taken to a floor where the door opens to flame and deadly smoke.

The Americans with Disabilities organization protests in high-rise buildings that they are provided access to upper floors, but not back down during a fire or emergency. The World Trade Center 9/11 investigation estimated 500 disabled, infirm and aged occupants were taken to areas of refuge and could not be removed to the street before the collapse. The Americans with Disabilities organization demands that owners of high-rise buildings install an elevator that can be used safely during a fire.

The reason elevators fail during fires are due to fire, smoke and water runoff from sprinklers and hose streams. My 15 years of high-rise firefighting experience found water runoff to be the major cause of elevator malfunction. An eight-year study of elevator malfunction causes at major New York City high-rise fires, conducted by the New York City Fire Prevention Bureau in the 1980s, documented that elevators failed one third of the time, even when used in phase II--Firefighter emergency use mode. Phase I is elevator recall mode. Phase III is an elevator demanded by Americans with Disabilities for safe use during fire, which does not yet exist.

The FDNY study stated elevator breakdown occurred when heat, fire and water entered the elevator hoist way. Water from Firefighters’ hoses and the sprinkler extinguishing system are the number one cause of elevator malfunction because wiring inside elevator hoist ways are not insulated and water causes short circuits and elevator stoppage. Building codes do not require waterproof insulation of electric wiring in elevators used by Firefighters in Phases I and II.

However, there is some good news for people with disabilities and Firefighters, finally, 15 years after the tragedy of 9/11. On the drawing board, there is a so-called “occupant-evacuation elevator” the American Society of Mechanical Engineers is recommending for New York City Building Code to be installed in high-rise office buildings more than 420 feet high. The following preliminary construction recommendations are being requested for an occupant-evacuation elevator that can be used by disabled people and Firefighters during high-rise office building fires:

  • The floor in front of the elevator door must have several-inch rises to protect the hoist way from water runoff coming from Firefighter hose streams and automatic sprinklers.
  • A generator must provide uninterrupted service during emergencies.
  • The elevator stops at every floor.
  • The elevator is enclosed in a concrete core at least 18 inches thick.

Despite this promising beginning, the Americans with Disabilities organization cautions the following

This is only a recommendation; it applies only to high-rise buildings more than 40 stories; it is considered only by New York City; and the real estate owners could have it stopped. So, use the stairways in case of fire.


Concrete and steel interfere with Firefighters’ radios.

chapter image Fig. 8.6  Curtain wall has space between edge of floor and inside of glass enclosure wall.

Steel and concrete in the high-rise structure interferes with Firefighter radio transmission. During a fire or emergency, Firefighters may not be able to communicate messages back to the Commander in the lobby because of the construction. It is a fact there can be no firefighting command and control of an operation without radio communications. When radios do not transmit at high-rise fires, ICs have to improvise radio relay systems, set up time-consuming secondary special radio repeater systems or stretch a hard wire during the most critical early stages of a fire. This is unacceptable.

Case study #1: Fire on the 51st story of the Empire State Building, the IC calls on radio, Command to Operations Officer (on floor below fire, 50th floor). No answer initially after several tries and several minutes of silence, there is a response, “Battalion 6, Staging, to Command, I read you. I will be your relay to Operations.” For three hours and five alarms, this relay communication system was required with no communication to the Operations Chief.

Case study #2: Incident Commander runs through falling glass to enter and set up lobby command and finds a Firefighter at the desk who tells him there is no communications with Operations Chief on the 21st floor due to construction. The Chief looks around and sees a house telephone on the desk, writes the phone number down and gives it to a Firefighter on the way up and tells him, “Call this number and give a progress report.”

Case study #3: Several months after the first terrorist cellar bombing in the World Trade Center in 1993, it was learned that there was no radio communication during the five-hour operation.

The Officer in charge of the FDNY Communications unit called me and said we now have a more powerful radio. I told him to meet me in the lobby of the Empire State Building to test the new, powerful radio. During the test, the new radio transmitted only up to the 65th floor of the 102-story building.

Today, Fire Chiefs have special radios to use when concrete and steel interfere with the everyday Firefighter’s radio. Chiefs can communicate, but Firefighters with less powerful radios cannot.

McKinsey & Company, a consulting firm, investigated the second terrorist attack of the World Trade Center on 9/11 and produced Increasing FDNY's Preparedness, which recommended stationary repeater systems be installed in existing high-rise buildings to enhance Fire Department radio communications.


In new high-rise buildings under construction, when they are inspected by the fire department to see if the standpipe works, simultaneously and before the certificate of fitness is granted by the local government to occupy the new building, there should be a test of fire department radios. The standard Firefighter’s radio--the one that is used at every fire--not a special radio carried only by Chief Officers or a mobile repeater radio--should pass a test before the certificate to occupy is granted. This standard Firefighter radio test should allow transmissions clearly from the building lobby, to the roof of the building and from the lobby down to the lowest below-grade level. If radio transmissions fail, there should be no certificate of occupancy issued and a stationary repeater system should be installed in the high-rise building to assist Firefighters’ radio transmissions.

The building systems fail.

chapter image Fig. 8.7  Sagging and cracked floors are a collapse warning sign and potential avenue of fire spread in a fire-resistive building.

At a low-rise building fire, Firefighters bring all the building systems they need: Their legs are a vertical transportation system; the hose is a water system; their radios are a communication system that always works; and if the building’s fire-resistive construction fails, they have a backup aerial master stream system outside to finish the job. Not so in a highrise building.

The Firefighters fail if elevators fail, the standpipe water system fails, the radios fail and the building construction fails if there are no master streams tall enough to reach the fire from outside. It is a fact at most major high-rise building fires, the building systems fail and cause Firefighters to fail, trying to extinguish the fire.

The greatest example of high-rise building system failure occurred in Philadelphia at the Meridian Plaza high-rise fire in the 1990s. At this fire, all the systems failed: the standpipe was incorrectly set with a low pressure regulating valve; Firefighters had to stretch a supply line up 20 floors to the fire, which took more than an hour; the elevators failed; masks and equipment carried by Firefighters walking up 20 floors caused exhaustion; Firefighters’ radios were ineffective due to the building construction; and when the building’s fire resistance failed and flames spread nine stories, it was beyond the reach of the outside master streams. Instead, Firefighters spent 11 hours fighting fire and heat in the sealed building.

The building designer failed, too. When this 38-story building was constructed, automatic sprinklers were installed only in the below-grade cellars and the eighth floor. This vital protection was omitted in the first 30 stories and fire burned in this so-called, fire-resistive building from the 22nd to the 30th floors.


Many years ago, I was at a fire and reminded how critical building systems, such as fire-resistive construction, are. At the same time, as a City-wide Tour Commander arrived and was assuming command of the fire from me, the Operations Officer interrupted us with a radio message, “Operations to Command, we are having trouble advancing the hose-line forward because of the wind blowing in from Central Park.” The Commander asked me with some alarm, “What do we do now”? I answered respectfully, “Chief, all 10-76 companies and all Sector Chiefs are in position to extinguish this fire. It’s up to the building’s construction now.” Today, I could order a “fire blanket” dropped down from the floor above to stop the wind or the “fire-blaster nozzle” set up on the floor below.

Stairway does not go to the roof.

Stairs in residence buildings lead up to rooftop stairs; in high-rise commercial buildings, stairs do not go to the roof. Some stairs deadend at intermediate floors; other stairs lead into a mechanical machine room; and stairs that do lead to the roof have a metal ladder and locked hatch cover enclosure.

chapter imageFig. 8.8  Schomburg Plaza, New York. A landmark incident on March 25, 1987, when seven people on the upper floors died as the fire spread from a basement compactor.

Fatal fire investigations in high-rise buildings sometimes reveal people do not follow an IC’s instructions to stay in place or go down a designated stairway. Instead, they make the fatal mistake and attempt to go up to the roof in a stairway. Some rescued victims tell the Fire Chief, “I was going up to the roof to wait for a helicopter.” No fire department in America has a plan to rescue people from roofs with helicopters. This may happen if people make a mistake and are trapped on the roof, but there is no plan. There is insufficient space on most roofs to land a helicopter.

If occupants of high-rise buildings do not receive fire evacuation training from the local fire department, they have no idea what to do in case of fire. They must stay in place until directed or assisted to leave. Then, they must go down the stairs, not up to the roof.

There are some occupants of highrise buildings who use elevators for years and do not know where the stairways are located. After a fire in a high-rise office building is extinguished, Firefighters must conduct a secondary search of all stairways from the fire floor up to the termination level. People sometimes are found overcome in stairways above a fire.


Stair exit doors can be locked.

Exit doors in high-rise office buildings can be locked to prevent unauthorized entrance from a stair enclosure to occupancies. An exit door leading from the occupancy to the stair enclosure must be open and the exit door from the enclosure to the street must be openable from both sides. If occupants or Firefighters enter a high-rise office building stair enclosure and the door closes behind them, they are locked in the stair enclosure and must walk down to street level where the door is openable to the street.

On October 17, 2003, occupants were ordered to leave a burning high-rise office building in Chicago and became locked in the stair enclosure. Smoke filled up the stair enclosure and they could not get down below the floor where the fire was burning. Firefighters had the door open to fight the fire. Smoke flowed over their heads up the stairs and they told the occupants to go back up. Occupants in the stairway could not re-enter the occupancies on any floor because the doors were locked. The investigation revealed there was a switch at the lobby desk that a building employee was supposed to pull that would open all exit doors from the stair side in case of fire, but it was not activated.

Today, the building laws in Chicago and the rest of the nation still allow doors to be locked from the stair enclosure side, but an electronic control switch instantly opens up all stairway locked doors when smoke detectors are activated or by pressing the button. Unfortunately, this law is not retroactive and many cities allow stair exit doors to be locked from the stair side and some now require every fourth door to be openable for re-entry and the remaining locked.

Locked exit doors, in addition to ignorance of what to do in case of fire in a highrise building, require the IC to make stair searching a high priority after a fire has been extinguished. It may not be possible to search stairs above a fire during the primary search, but as soon as the fire is extinguished, this must be given high priority as part of the secondary search.


Smoke-proof towers can create wind-driven fire.

chapter image Fig. 8.9  Window keys are obtained at the lobby desk by first-arriving ladder company.

Firefighters should not use a smoke-proof stair as an attack stair to advance a hose-line because the air shaft in the intermediate vestibule can pull fire and heat into the stair from a broken window during a fire and prevent Firefighters from advancing a hose-line from the stair enclosure. A high-rise office building, unlike a high-rise residence building with openable windows, is a sealed building and windows should not be vented during the initial attack because it could start a wind-driven fire that stops Firefighters’ advance. The windows in a modern high-rise office building are locked and not designed to be open. This creates a sealed atmosphere inside a building that has a different temperature and pressure from outside of the building. If a window is broken in this sealed building during a fire--by heat or venting and there is an open door from the smoke-proof stair--this can set up a flow path of wind from the broken window to the smoke-proof tower air shaft. This wind-driven flow of heat and flame coming from the window to the stair enclosure shaft can stop Firefighters and cause them to withdraw back to the stairway.

When there are two stairs and one is a smoke-proof tower, the latter should be used for evacuation of occupants, not to attack the fire. If the smoke-proof tower is the only stair to have a standpipe and must be used as an attack stair, it is important that windows not be vented by Firefighters. If a wind-driven fire does occur and stops Firefighters from advancing, the door from the smoke-proof stair must be closed and another attack hose-line stretched from the other stair enclosure. If the high-rise fire can be reached by an aerial stream, an outside stream may become the strategy after all Firefighters inside have been moved to safety.

High-rise residence buildings are more deadly than office buildings.

A three year (1996-1998) study by the U.S. Fire Administration showed, on average, more people die in high-rise residence building fires than non-residence high-rise building fires (3.9 persons per 1,000 high-rise residences vs. 1.6 persons per 1,000 non-residence high-rises). One of the reasons for the increase in fire deaths is that high-rise office buildings have more lifesaving fire protection installed in the structure than the residence buildings.

For example, in the residence high-rise building:

  1. There is no emergency communication public address system from lobby to apartments for a person in charge to tell occupants what to do during a fire. When a fire occurs, the IC cannot give people who feel trapped in their apartment advice. The most frequent advice that should be given to people in apartments of a high-rise building during a fire is that they should stay in the apartment and not go into the halls or stairs. Or, in a rare instance if evacuation is necessary, occupants must be informed what stair to use for exit. Some stairs will be clear of smoke; some stairs will be full of smoke and occupants must know this.
  2. There are no automatic sprinkler systems required to be installed in a residence building as they are in most high-rise office buildings.
  3. There are no fire drills held by management to inform occupants what to do or not to do during fire as there are in high-rise office buildings.
  4. There is no person in charge 24/7 in a residence high-rise building as in an office building.
  5. The stair enclosures are not marked with letters and floor numbers, inside and outside on the doors leading to exits. This makes it impossible for an IC to designate an avenue of escape for occupants. The IC cannot inform occupants what stair to use because it is clear of smoke and what stair not to use because Firefighters are using it and it will become full of smoke.  
  6. There is no written evacuation plan stating what to do in case of fire; when to leave and when to stay. The only lifesaving fire protection device installed in a high-rise residence building is a self-closing apartment entrance door.

A high-rise fire battle plan:

Despite the above high-rise construction “plan disruptors,” Fire Officers must plan for high-rise firefighting.

The first line

The first hose-line, four lengths of rolled-up hose, is taken to the floor below the fire and connected to the standpipe. The hose is stretched up the stair and the fire is attacked. The largest hose available (2½-inch diameter) should be used to attack a high-rise fire. And, a solid-bore nozzle should be used because if the building is taller than an aerial ladder, it may not be possible to vent windows, which is important when using a fog nozzle to prevent burns. Four lengths of hose may be needed for a typical, large floor area. You get one chance to extinguish a high-rise fire with a hose-line. You do not want to stretch short of the fire.

The second line

The second attack hose-line, also rolled-up hose, should be connected to the standpipe outlet two floors below the fire or on the fire floor if fire conditions permit. This second hose-line is used with the first attack hose-line. Because the floor area of a high-rise office building is very large, there may be a large body of fire that requires two hose teams operating side by side for extinguishment.

Portable ladder

A portable ladder may be placed on the lower floors of a highrise and, in a rare instance, at the second-floor window of a high-rise if the lobby command station of the high-rise office building is located on the second floor. In this situation, a large group of people leaving upper floors may crowd up here and request assistance from Firefighters. Also, the stair from the second-floor lobby to the firstfloor street exit may be crowded and portable ladders placed at the second-floor lobby area can evacuate people and prevent a panic and rush to the stairway.

Window venting

Venting windows should not be undertaken if the street below is crowded with people. Firefighters first on the scene should request window keys from the building manager at the lobby desk before going up to search for the location of the fire. Because of the danger of injuring people in the street and on the sidewalk with falling glass, before any venting involving breaking glass in a high-rise, permission of the IC must be requested. Windows may be vented if the falling glass will land on a building setback or the roof of an adjoining building or the Officer in command has the street cleared. Most high-rise firefighting is accomplished without venting to prevent injury to people in the street. Venting should be coordinated with the hose-line advance on the fire. When the hose is charged and the Firefighters begin to move in, vent as many windows as possible from the aerial ladder.


Aerial ladder

chapter image Fig. 8.10  The New York High-Rise nozzle is designed for use at wind-driven fires occurring on high-rise building floors that are above the reach of an aerial or tower ladder.

An aerial ladder should be raised for rescue, to extinguish auto-exposure or a combustible cladding fire. For example, if the interior attack hose stream cannot be advanced by Firefighters after Firefighters inside are removed to safety, the aerial master stream can be used. Also, even if the fire floor is several stories above the aerial ladder tip, it may stop window-to-window auto-exposure or exterior cladding fire of a combustible exterior insulation finish system (EIFS).

When a high-rise, wind-driven fire cannot be extinguished by interior hose-lines and the fire floor is above the reach of an outside aerial or tower ladder, a New York High-Rise nozzle may be used to extinguish the fire from the floor below the fire.

The game-changer

A game-changer at a high-rise fire is a report of sagging and cracked concrete floors above a fire. Firefighters should not operate above or below the floor. A sagging or cracked floor is in danger of collapse. Another game-changer in a high-rise building is a wind-driven fire. If Firefighters cannot advance a hoseline onto the floor due to wind from broken windows, strategy must be changed. A new game-changer is a combustible cladding fire. At a combustible cladding fire, the defend in place strategy is not an option. This should result in positioning a tower or aerial ladder near the window, causing the wind inflow. After confirmation that interior forces have withdrawn to the hallway and closed the door, the fire is extinguished from upwind. If the fire is above the reach of the ladder, a “fire blaster” nozzle could be used from the floor below. A combustible cladding fire is a game-changer that may require total evacuation of the structure.

High-Rise Battlespace Casualties

Brooklyn, New York, three Firefighters die in hallway of high-rise building. NIOSH 99 FO1

Chapter 9: Fire Escape Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Fire escapes are a valuable part of the Firefighter’s battlespace. Firefighters use fire escapes for outside venting, hose-line stretching when there are too many hose-lines stretched up an interior stair, forcible entry through a window and access to search and rescue. Fire escapes are complex mechanical structures with movable parts and Firefighters must know how to use them safely.

Different types of fire escapes are designed for different methods of evacuation during fire. Some are designed to allow people to move up or down floor levels; others are designed for horizontal movement from fire. And, finally, all fire escapes have structural weakness and can fail in different ways and Firefighters must know this, too. Your community may not have buildings with fire escapes. However, a mutual-aid call to a nearby municipality could have you climbing a fire escape you have never seen before when the Incident Commander (IC) orders you to lower a sliding drop ladder or release a counterbalance stairway, so you must understand this battlespace.

There are four common types of fire escape construction and four different strategies an IC may consider to assist people calling for help on a fire escape. There is a party wall horizontal balcony fire escape, a standard fire escape, an exterior screened stairway and a wood porch fire escape.


Party wall balcony fire escape

chapter image Fig. 9.1  A horizontal emergency exit must have a pathway through the adjoining occupancy. This one does not.

A party wall balcony is strictly a horizontal emergency exit, with an exit pathway afforded through the adjoining occupancy. It has no stair ladder between platforms. You cannot get down or go above to the next level fire escape balcony because there is no ladder. People must proceed to the adjoining window of the adjoining building, separated by a fire-resistive party wall. Unfortunately, most people do not understand the horizontal fire escape concept or realize there is a fire-resistive wall separating both sides of the fire escape they are standing on, calling for help. The adjoining building window leads to an area separated by a three-hour brick wall or partition.

If a ladder is unavailable, the IC must send a Firefighter to the floor of the adjoining building to open the window leading to the horizontal exit and escort people from the fire escape, into the adjoining area of refuge and lead them down the adjoining building stair to safety. Because most people don’t know how to use a party wall balcony fire escape, it quickly can become overloaded. Incident Commanders must order people removed from party wall balconies before they collapse. Removal by ladder and Firefighters sent to adjoining apartments can be tactics to remove people on party wall balcony fire escapes. However, removal to adjoining apartments by Firefighters is the preferred and safest method.

Standard fire escape

A standard fire escape has a metal stair connecting balconies. However, these stairs are at a steep angle with narrow steps and, in some instances, there is only one railing for a guide, making them very dangerous to use. Descending a fire escape stair presents a fall hazard because of the sub-standard stair design. Fire escapes are not maintained and they become corroded and collapse when used. The fire service knows from experience that the most common injury to Firefighters using fire escapes is loss of balance and falls due to step collapse. Metal fire escapes suffer rust and corrosion, which weakens bolts connecting a step to the stair side stringers.


An occupant of a burning building descending a fire escape with a child must be considered life in danger and requires immediate action by an IC. Even though there may be people trapped inside, life and death decision-making requires a visible life hazard to be addressed first, before any life hazards inside that are not visible from the Command Post. An IC must order a Firefighter to climb the fire escape and assist the person. Firefighters must know how to escort people from a fire escape. They should not be taken down the fire escape; instead, they should be taken back into the building on a floor below the fire and then down the interior stair. Occupants never should be allowed to descend a fire escape without assistance from Firefighters.

Exterior screened stairway

An exterior screened stairway is enclosed by a high metal screen or railing and extends from the top floor of the building to the street by way of a permanent, stationary metal stair. Unlike other fire escapes, the exterior screened stairway has no sliding "drop" ladder or movable counterbalance stairway from the lowest balcony to the street. An exterior screened stair fire escape is required on public assembly occupancies, such as schools, theaters, movies and places of worship.

This fire escape is superior to other emergency exits and is similar to an interior stair. It is required to be enclosed by a metal screen with the stair extending from the top floor of the building to the street. It does not go to the roof. The metal stair is wide enough for two people to descend side by side, the stair treads are at least eight inches wide and it includes a handrail.

When many people are descending an exterior screened stair fire escape, the IC’s strategy may be different. Instead of sending a Firefighter up the screened stairway, assist the people away from the base of the stair. Keep them moving away from the area where the fire escape stair terminates and don’t let them stop or linger there. It is important that the flow of people coming down the fire escape and out of the burning building not be interrupted.

chapter image Fig. 9.2  It is safer to take occupants into a window of an apartment below the fire and walk them down the stairs, instead of via a vertical drop ladder.

When an exterior stair fire escape serves a school, place of assembly or nightclub and people are descending a stair, Firefighters should not climb the stair against the flow of people to assist. This may stop the flow of people away from the fire danger. Firefighters should move them away from the area to allow more people to move down the fire escape stair. Studies show that if you stop the flow of movement of people for a short time, this stoppage passes back up the line and is magnified. A 30-second stoppage of people exiting can increase the time of stoppage backup greatly. This could cause panic and trap people trying to escape a fire.


Many years ago as a Firefighter, I worked in a fire company in upper Manhattan that was adjoining a schoolyard with an exterior screened stair. The school held fire exit drills for the students and moved the small children past the front door of the firehouse. The Captain of the firehouse had a fire pre-plan in case they received an alarm to respond to a fire in the nearby school while children were being evacuated out of the school and passing in front of the firehouse simultaneously. The plan was to leave the long, slow-moving, tiller-operated, wooden aerial ladder in quarters so as not to interrupt the children’s exiting movement with the responding aerial ladder, but instead, notify the dispatcher to send another ladder truck for replacement, leave their ladder truck and run next door to the fire, carrying tools. A study of Our Lady of Angels fire in Chicago, December 1, 1958, where 92 children and three nuns were killed in a fire, revealed the importance of not interrupting the flow of children evacuating a burning school.

Wood porch fire escapes

A wood porch with connecting stairs is required to have a fire-rated wall and self-closing exit doors, separating it from the occupancy to the porch, to be considered a fire escape exit. This separation allows people on upper floors to use the rear porch stair when there is a fire in a lower-floor apartment.

Wood porch fire escapes were accepted by building codes as a second exit in the last century on Type III and Type V buildings. The wood porch fire escape, usually found on “double- or triple-decker” apartments in New England and the Midwest, have two concerns for an Incident Commander: One, they burn and spread fire to all floors and two, they collapse. Wood porch fire escapes are flammable and used to store combustible materials, rubbish and cooking stoves that sometimes start fires that spread up the entire rear of the building and into the apartments on all floors.

Some may be constructed of fire-retarding wood. However, when exposed to the weather, the wood porch fire escape quickly loses its fire resistance and also becomes a collapse danger due to dry rot if not maintained. Rusting is the problem with metal fire escapes; dry rot is the collapse concern with wood fire escapes, in addition to fire spread.

Firefighters quickly can overload a wood fire escape with heavy hose-lines and create dangerous impact vibrations when overhauling in the wood stairs or balconies. An IC’s strategy for people exiting by way of a burning wood fire escape must include stretching a hose-line to extinguish fire. Any time Firefighters climb a wood porch fire escape, they must consider collapse danger, even if the fire escape is freshly painted. Dried-out wood exposed to the elements is considered aged “firewood” and can spread fire rapidly.


Sliding drop ladder

chapter image Fig. 9.3  The sudden impact of a counterbalance stairway striking the ground can cause the entire metal stairway to collapse off the building or the heavy counterbalance weights fall off the ladder.

The most common first-level access to a standard metal fire escape is a vertical sliding drop ladder. Firefighters must be trained regarding how this mechanical device works in order to gain access and climb a fire escape to assist people. A sliding drop ladder is a vertical metal ladder held in place on the lowest balcony of a standard fire escape by a pendulum hook.

To release a sliding drop ladder, a Firefighter uses a pike pole to push up a rung on the ladder several inches. By raising the vertical drop ladder rung, it frees the pendulum hook and it swings away. The weight of the ladder now is transferred to the tip of the Firefighter’s pike pole. The Firefighter moves the pike pole quickly out from under the drop ladder rung, allowing the ladder to drop straight down.

A vertical drop ladder is encased on each side by metal tracks or guides to ensure when released, it drops straight down and not outward at a 90-degree angle on top of a Firefighter. Before a Firefighter releases a drop ladder, it should be sized up to ensure the drop ladder is properly encased between the guides and in the track before lowering it. At night, when visibility is poor or smoke condtions obscure visibility, a Firefighter should stand beneath the fire escape balcony for protection before using the pike pole to release the drop ladder in case it falls uncontrollably out of its track.

Pendulum hook

A pendulum hook holds a sliding drop ladder in place above a sidewalk or rear yard, out of the reach of adults and children. The hook is a three-footlong bar with a hook at the end, attached to the fire escape balcony, which is placed under a rung of the sliding drop ladder. After a fire escape is used by Firefighters, the drop ladder must be pulled up and a rung of the ladder reattached to the pendulum hook. The sliding drop ladder must be ready for another fire that might require use of the fire escape.


To reset a drop ladder, a Firefighter on the second-floor fire escape balony pulls up the drop ladder, hand under hand, rung by rung, then holding the ladder with one hand, uses the other hand to swing the pendulum hook over and place it under a rung.

The Firefighter must use a fire department ladder to descend the fire escape or go through a window of an apartment to the interior stair to get to the street. Firefighters should not use the drop ladder to climb down and drop several feet to the street. There have been disabling foot injuries to Firefighters doing this unsafe act when their weight causes the attachment holding the pendulum hook to the fire escape to break.

If a drop ladder is not replaced properly after Firefighters leave the scene, a thief may use it to gain access into the apartments or children could be injured playing on the fire escape. It is the responsibility of the IC to order a Firefighter to reset a sliding drop ladder. In some fire departments, the standard operating procedure specifically designated the last ladder company leaving the scene this responsibility. If the drop ladder is not repositioned, it reflects badly on the entire operation.

In some instances, the drop ladder comes out of its tracks and guides and cannot be reset properly. A written notification to fix this life safety exit should be given to the building manager. If this is not done, a Firefighter could be injured at the next fire when the ladder falls away from the guides.

Counterbalance stairs

Instead of a sliding drop ladder, some standard fire escapes have access to a street from a counterbalance stairway. A counterbalance stair provides street access from a fire escape on a commercial occupancy; a sliding drop ladder provides street access from a fire escape serving a residence occupancy; a permanent stationary stair provides street access from an exterior screened stairway serving a place of assembly or school.

A counterbalance stairway is large, horizontal, movable metal stairway suspended at the lowest level of a standard fire escape on a factory, loft or storage building. This horizontal stair is supported on a pivot, balanced in a horizontal position by heavy, castiron, counterbalancing weights at one end of the stairway. Several hundred pounds of metal either is attached to one end of the horizontal stairway or to the side of the building, held by a steel cable and pulleys. When a person walks from the fire escape to the counterbalance stair, the weights are raised.

There may be a manual bar atttached to the stair and fire escape that holds the stair up. This bar can be moved from the street by a Firefighter with a pike pole. Then, the counterbalance ladder can be pulled down to street level with a pike pole or if there are no Firefighters available, by the weight of a person walking out on the counterbalance stair.

Some of these heavy metal structures have not been tested or operated for long periods and rust and deterioration can cause them to collapse upon activation. The sudden impact of a counterbalance stairway striking the ground can cause the entire metal stairway to collapse off the fire escape, the heavy counterbalance weights fall off the ladder, the cable holding the weights can snap and become a deadly whip or pull the entire assembly of weights and pulleys off the building wall.


Fire experience has shown when encountering people awaiting rescue on the lowest balcony of a fire escape with a counterbalance stairway or a drop ladder, Firefighters should use a ground ladder instead of either of the fire escape ladders. There is no danger of ladder collapse and the angle of the fire department ladder is safer than a drop ladder.

Gooseneck ladders

chapter image Fig. 9.4  Some gooseneck fire escape ladders do not have enough clearance for boot space between the vertical ladder and the building exterior wall.
chapter image Fig. 9.5  One missing or broken step serves as a warning that there is another one.

Not all fire escapes go up to the roof of the building. Some fire escapes terminate at the top-floor level. For example, a fire escape at the front of a multiple dwelling that has a decorative cornice at roof level will not have a gooseneck ladder leading to the roof. However, most fire escapes at the rear or side alley of a flat-roof multiple dwelling will have access to the roof by a gooseneck ladder.

A gooseneck ladder is a vertical ladder on the top-floor fire escape balcony, leading to the roof, which has a curved top extending over a parapet wall; it is attached to the exterior wall of the building and to the roof deck. Sometimes, these connections are loose, missing or corroded and the ladder moves outward from the building during a climb. This sudden movement could cause a Firefighter to lose his/her grip and fall backward off the fire escape and into the backyard.

Before climbing a gooseneck ladder, you should test its fastening by pulling the ladder away from the wall. A design problem with a gooseneck ladder is not enough clearance between the vertical ladder and the building exterior wall. There may not be enough space between the ladder and wall to allow placing the ball of your foot on the rung. Only the toehold can be had on a rung. When this foot spacing problem exists, you cannot climb the ladder by gripping the rungs. You cannot carry a tool with one hand and climb this ladder. You must continuously grip the rail with both hands when climbing a gooseneck ladder.


Vertical fire escape ladders:

chapter image Fig. 9.6  The exterior screened stairway has no sliding “drop” ladder or movable counterbalance stairway from the lowest balcony to the street.

Gooseneck ladders and sliding drop ladders are vertical ladders that present an unusual climbing danger to Firefighters and occupants of a building. There is a “pullback effect” when climbing a vertical ladder that a typical ladder does not present. When you place a fire department ladder, you place it at an angle that keeps the body vertical and the center of gravity going through your body, which keeps you on the ladder rung. You are vertical and the ladder is at an angle.

It is different when you climb a vertical ladder; here, the center of gravity runs through your upper shoulders and the SCBA tank you carry, creating a pullback effect. The ladder is vertical and you are at the angle. The Firefighter is leaning backward when ascending or descending a vertical ladder with a continuous pullback effect. Gravity is pulling a person backward and if a Firefighter is wearing a breathing apparatus or carrying heavy tools in a backpack or with a back sling, there is a great danger of falling backward off the vertical ladder. Gooseneck and sliding drop ladders are vertical ladders with a pullback effect.

In 2010, during a grease duct fire, Chicago Firefighter Christopher Wheatley fell to his death from a gooseneck ladder extending from the top balcony to the roof. It was estimated he was carrying 75 pounds of tools and equipment. The increased amount of weight carried on the shoulders of a Firefighter magnifies the pullback effect when climbing a vertical ladder. The three-point contact method of climbing should be practiced by Firefighters--two hands and one foot or two feet and one hand.


The future of fire escapes

Today, fire escapes serving as a second exit no longer are allowed on new buildings (section 3406, International Building Code). However, existing buildings will continue to have fire escapes that have deteriorated during the past century and these structures become more dangerous. They will continue to rust, corrode and rot and Firefighters will continue to use them during fires. Firefighters will have to climb them in the darkness of night or when they are coated with snow and ice. The moving parts of fire escapes will become unworkable and more fragile.

Owners of buildings with fire escapes know their dangers and want cities to allow them to remove them. While no longer required by law, many fire escapes are still on commercial buildings that have been converted to expensive loft building residences.

It is expensive to properly maintain a fire escape. Firefighters and people using fire escapes during emergencies are killed and injured and now fire escapes are collapsing when used during parties and celebrations. Fire escapes are lawsuits waiting to happen. In the meantime, Firefighters must use them with extreme caution.

A fire escape climbing battle plan:

  1. When climbing a fire escape, place one foot on the step above and apply pressure to that step first, before putting full weight on it. Continuously grip the fire escape railing in case a step fails.
  2. Firefighters should know a missing or broken step serves as a warning there is likely to be another one.
  3. Do not lean against the enclosing rail before testing it.
  4. Test a vertical ladder (gooseneck) leading from a fire escape balcony to the roof before ascending or descending it.
  5. If a Firefighter has any uncertainty about a stair or a sliding drop ladder, use a fire department ground ladder.
  6. Never stand beneath a counterbalance stairway or its cable, pulley wheel or heavy metal balancing weights when it is being activated.
  7. Use the three-point contact method when climbing; two hands and one foot or two feet and one hand.

The game-changer

The game-changer is people descending a fire escape and Firefighters discovering a broken fire escape step. People cannot be allowed to descend a fire escape unassisted. Firefighters must be sent to assist people on a fire escape. A broken fire escape step is a warning sign there must be other broken steps and the fire escape is unsafe to use. Take people in from a fire escape to any floor below the fire and walk down the stairs. Conduct fire escape rescues by aerial platforms, a safer method.

Fire Escape Battlespace Casualty

Chicago, Illinois, Firefighter falls from fire escape vertical ladder. NIOSH 2010-25



  • Counterbalance stair: A counterbalance stairway is a large, horizontal, movable metal stairway, suspended at the lowest level of a standard fire escape, supported on a pivot, balanced in a horizontal position by heavy, cast-iron, counterbalancing weights at one end of the stairway.

  • Exterior screened stair: An exterior screened stairway is enclosed by a high metal screen or railing and extends from the top floor of the building to the street by way of a permanent, stationary metal stair. Unlike other fire escapes, the exterior screened stairway has no sliding "drop" ladder or movable counterbalance stairway from the lowest balcony to the street and it does not go to the roof.

  • Gooseneck ladder: A gooseneck ladder is a vertical ladder, which has a curved top extending over a parapet wall, on the top-floor fire escape balcony leading to the roof. It is attached to the exterior wall of the building and the roof deck.

  • Party wall balcony: A party wall balcony is strictly a horizontal emergency exit, with an exit pathway afforded through the adjoining occupancy. It has no stair ladder between platforms.

  • Pendulum hook: The hook is a three-foot-long bar with a hook at the end attached to the fire escape balcony above, which is placed under a rung of the sliding drop ladder.

  • Sliding drop ladder: A sliding drop ladder is a vertical metal ladder held in place on the lowest balcony of a standard fire escape by a pendulum hook.

  • Standard fire escape: A standard fire escape has a metal stair connecting balconies. These stairs are at a steep angle with narrow steps and, in some instances, one railing for a guide, making them very dangerous to use.

  • Vertical ladders: A sliding drop ladder and gooseneck ladder.

  • Wood porch fire escape: A wood porch with connecting stairs is required to have a fire-rated separating wall and self-closing exit doors leading to the porch to be considered a fire escape exit

Chapter 10: Glass and Steel Building Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


The hazard of a glass and steel building battlespace is not its structure or content, but deadly toxic smoke emitted from miles of electric wires covered with combustible insulation. The new glass and steel high- and low-rise office building has electric wire with combustible insulation extending throughout every ceiling space, behind walls, below floors and rising in utility closets of the building. In these hidden spaces, you can find a fire and smoke hazard consisting of electric wires covered with combustible material, such as polyvinyl chloride (PVC), rubber or paper, to protect the heated wire. When burning, this insulation gives off large quantities of blinding, deadly, toxic smoke very rapidly.

If there is polychlorinated biphenyl (PCB) left as part of generator or cable insulation, installed before 1979 and not removed as required by law, the smoke generated by a fire may be declared a hazardous material, requiring occupants of a building, Firefighters and equipment exposed to PCB smoke to undergo decontamination procedures. Smoke from burning combustible insulation is the deadly enemy in the glass and steel building battlespace.

You may be an expert in brick and wood building construction after years of firefighting, but if you are transferred into a district of new modern glass and steel buildings, a Type I or Type II glass and steel construction battlespace, you will have to expand your vocabulary and knowledge of building construction. In addition to familiar terms, such as parapets, coping stones, headers, trimmer, cockloft, studs, lath, furring strips and knowledge of how they are affected by fire spread, you must include new information about glass, steel, plenums, curtain walls, fluted metal floors, wind-driven fire flow paths, interstitial spaces, utility closets, polyvinyl chloride, polychlorinated biphenyls and, most importantly, how to fight electric cable fires. Let’s start with glass and steel building construction terms and end with firefighting.

chapter image Fig. 10.1  The battlespace danger is not the structure or its contents, but the tons of electric wiring covered with combustible, toxic insulation.


Structural window glass of a curtain wall is heavy. It differs from thin, windowpane glass used in residential buildings. Window glass in a residence building can be 1/8 or even 1/16 of an inch thick. Structural curtain wall glass can be ¼- to ½-inchthick and weigh three to six pounds per square foot. For example, a four- by eight-foot, ¼-inch-thick glass window in a commercial building can weigh 96 pounds and ½-inch glass can weigh 192 pounds. If you break a large glass window curtain wall for the purpose of venting a smoke-filled fire area, you may be sending 30 pounds of broken glass into the street on top of people you just evacuated from the burning building or on Firefighters outside, stretching hose or raising ladders. Before an Officer in command orders venting, he or she must ensure the street below is controlled and clear.


Venting is a very important part of firefighting and must be carried out to remove deadly smoke and gases from a building. The windows in a glass and steel building are not designed to be opened by occupants. This type building is sealed and depends on a heating, venting and air-conditioning system to provide air circulation. Curtain wall glass windows are locked or sealed permanently. Firefighters should obtain window keys from building management at a fire to open locked windows to vent smoke. These buildings must be vented during fires, but before thick, heavy windows can be broken, the sidewalk and street below must be cleared of people. When venting is not possible, firefighting in a glass and steel building must be accomplished similarly to a cellar fire without venting.

There are instances where window glass can be broken without danger of injuring people. For example, vent if the glass falls on the roof of an adjoining building; vent an upper floor if there is a setback portion, preventing glass shards from falling to the street. At night or early morning at a fire, the Incident Commander (IC) has control of the area below before window venting, causing glass falling to the street, can be ordered. Falling glass can kill and injure people in the street. The IC must be notified before windows are to be vented.


Steel is an alloy (mixture) of iron and carbon, used because of its high tensile strength. Tensile strength is its ability to resist loads trying to “stretch” it; compressive strength is the ability to resist loads trying to reduce its size by “pressing” it together. Steel is noncombustible in that it does not add fuel to a fire. However, steel does not have fire resistance; it fails during a fire. Fire resistance means it resists fire. Fire can cause steel to fail, bend, buckle, warp or twist and lose its load-bearing capability.

When heated by fire at temperatures to 1,000 degrees Fahrenheit or 538 degrees Centigrade, steel loses 50 percent of its load-bearing capacity. For the steel to lose this load-bearing capability, the piece of steel itself must be heated to that 1,000 degrees Fahrenheit or 538 degrees Centigrade temperature. If you want to make steel fire-resistive for one to four hours, you cover and insulate it with concrete, terracotta, plasterboard or a spray-on, fire-resistive material.

The spray-on, fire-resistive method is the most economical insulation, but the least effective. Spray-on, fire resistive insulation is ineffective for several reasons. The steel may not be prepared properly before application. It must be cleaned also. Sometimes, the fire-resistive slurry is not mixed properly, the material is not applied over the entire steel member or the proper thickness of the fire-resistance spray-on is not determined. When NIST investigated the 9/11 World Trade Center collapse, it found there was no documentation or recorded tests performed to determine the exact thickness of spray-on required to give steel a two-hour rating. Beware of the stated steel fire-resistance rating and load-bearing capability during a fire.


chapter image Fig. 10.2  Before an Officer in command orders window venting, the street below must be controlled and clear.

A glass and steel building can have a corrugated steel roof underside, but above, it can be a combustible roof deck of asphalt, tar or plastic insulation with a paper moisture barrier. After a top-floor fire in a glass and steel building is extinguished, ceiling tiles must be opened and the underside of the roof examined for burn marks. A top-floor fire could conduct heat through the metal roof, ignite this combustible roofing and spread fire over the entire building.


The roof covering and the electric cable in a glass and steel building are the greatest structure fuel load in the building. The goal of any top-floor fire is to stop it from spreading to the roof covering. Conduction (the transmission of heat through a solid) is the method of heat transfer through a steel roof that can ignite a combustible roof covering above. An IC should use a thermal imaging camera to check for heat near any burn marks on the steel and, if necessary, send a Firefighter to the roof to examine the roof covering directly above for extension. Most glass and steel buildings are Type II construction and the NFPA changed the official name of Type II construction from noncombustible to “limited combustible” construction because of this combustible roof covering.

Ceiling plenum

chapter image Fig. 10.3  A plenum space can contain combustible cables coated with insulation that produces toxic smoke.

A plenum space is a concealed space above a suspended ceiling in a glass and steel building that facilitates air circulation for heating and air-conditioning systems (HVAC). A plenum provides a pathway for HVAC airflow to or from a ventilation shaft that leads to a mechanical machine room and air-conditioning system. Inside this plenum space can be miles of combustible cables coated with combustible insulation. This is a major fuel hazard inside the concealed space of a plenum area that can spread flames rapidly and generate smoke inside the building’s air system. Once a content fire is confined in a floor area, Firefighters should examine the plenum area with a thermal imaging camera or by lifting a ceiling panel with a pike pole and check for fire in this concealed space.


Interstitial space

An interstitial space is a concealed space between floors used to contain large mechanical and electrical equipment found in glass and steel buildings. The space can be up to eight feet high and contain a walkway for access for maintenance, repairs and renovations. Plenums sometimes are called interstitial spaces when they contain electric and HVAC utilities.

When searching a smoke-filled computer office in a glass and steel building, the IC must determine from management if the room has a concealed space below the floor containing electric supply cables. Some computer rooms have these raised floors containing spaces with combustible electric cable insulation. If a building manager states there is fire in the interstitial space or if you enter a room to search and you see smoke coming up from the floor, fire may be below the floor in this space.

An (interstitial) floor space also may serve as an air-handling space, similar to a ceiling plenum and, if so, the HVAC system must be ordered shut down or it will be an air force-fed fire. In many computer rooms, the interstitial space is protected by an automatic extinguishing system with controls outside the room.

Curtain wall

A curtain wall is used to enclose a glass and steel building. A curtain wall is an aluminum-framed exterior wall containing in-fills of glass panels. This glass and aluminum wall is similar to a curtain covering the exterior of the structure. It is attached to the floor slab only by bolts, which sometimes leave small spaces between the outer edge of the floor slab and inside of the curtain wall. This type of lightweight glass curtain wall does not carry any floor or roof loads of the building.

The fire protection problem with a curtain wall is the small space between the outer edge of the floor slab and the inside of the curtain wall. Fire and smoke can spread to a floor above through this small, several inches wide space if it is not filled with fire-stopping material. In some instances, the fire-stopping is not there. A new fire protection problem is combustible cladding affixed to the exterior of a curtain wall (EIFS).

This space created by a curtain wall was one of the avenues of fire spread in a high-rise building fire that extended nine floors; the 1990 Philadelphia, Meridian Plaza fire. When checking a floor above a fire for extension in a glass and steel building, Firefighters must check the space at the outer edge of the floor slab, near the inside of the glass curtain wall. This space is located in the outer offices of a floor area behind the peripheral air conditioning near the windows.

Fluted metal floor

There is some concrete in a glass and steel building. Several inches of concrete is poured on top of a fluted metal under-floor. Instead of an eight-inch-thick concrete floor, a lightweight glass and steel building has a combination three-inch concrete and ½-inch metal floor. The metal gives a concrete floor increased tensile strength and bending the metal into flutes or curves gives the steel greater strength.

chapter image Fig. 10.4  When heated by fire to temperatures of 1,000 degrees Fahrenheit or 538 degrees Centigrade, steel loses 40% of its load-bearing capacity.

During a serious, long-duration, multiple-alarm fire in a glass and steel building, the concrete floor above a fire cracks and spalls, causing it to heave upward and the fluted metal under flooring sags and could collapse. Several 10- by 20-foot sections of a fluted metal under-flooring sag downward and have to be replaced.

For example, a 1993 multiple-alarm fire in a glass and steel structure (Bankers Trust Company, New York City) caused severe failure of the floor system. The floor concrete above the fire cracked and allowed fire and smoke to extend to the floor above and the fluted metal under-flooring sagged downward so badly it had to be shored up before Firefighters were allowed to overhaul below it. One of the lessons learned at this fire building was floors fail during fire. When searching above a fire, Firefighters must notify the IC of any sign of an unstable floor, such as cracks, uneven or sloping floor or concrete heaved upward. A floor is declared unstable and Firefighters should not enter an area when the above conditions are discovered. A floor section does not need to collapse. It is a collapse danger if it is cracking and issuing smoke from a fire below or the floor surface is uneven or slanted. When any of these signs is discovered, Firefighters must discontinue a search on the floor.

Wind-driven fire

A glass and steel building is a sealed building and an HVAC system provides all air cooling and heating. Windows are locked or sealed. The structure is considered a windowless building from a fire protection point of view. In a sealed building, when one window is broken or falls out of the frame due to heat of a fire, it can create a wind-driven fire, sending flame across a floor or into a hallway in a deadly flow path. Flame can be driven by wind, similar to a blowtorch, from a vented window out into a hallway, up a stair, into a stair enclosure, which has an opening to a smoke shaft, or up an open elevator shaft. Anytime there is an outlet like a vented roof opening and a window is vented during a fire, a wind-driven fire can be created.


A fire company cannot advance a hose-line against the flow path of a wind-driven fire. Venting must be controlled by an IC in a glass and steel building and not done indiscriminately. To prevent a wind-driven fire, Firefighters may pressurize a stairway with power fans and control all closed doors. A pressurized stair may resist or sometimes reverse a wind-driven fire, but setting up fans takes time. A Firefighter caught in the flow path of a wind-driven fire will be burned severely or have the escape blocked.

A Firefighter who is in the floor area, but not in the flow path of flame and heat, may not be affected. It is the path in which the flame moves that is the danger area. This may be a hallway or stair opening. Firefighters must stay out of the flow path.

An example of a flow path occurred at a fire where a vented window blew heat and flame down a long hallway into a stair enclosure with a smoke vent inside. The flow path was from the window down the hall into a stair enclosure, up a smoke vent. For 30 minutes, Firefighters were unable to advance the hose out the stair enclosure to extinguish the fire because of this blowtorch, wind-driven fire. However, a searching Fire Officer who approached the fire room from another stairway and another hallway that intersected with the path of the wind-driven fire at a right angle was able to walk up to the fire and saw the flame flow path coming from the fire room, going down the hall into the stair. He requested the IC order a company to stretch a hose-line to that point and said they easily would extinguish this wind-driven fire from a flanking advance.

chapter image Fig. 10.5  The new glass and steel high- and low-rise office building has a large amount of electric cables in concealed spaces.

This hose-line was stretched and, indeed, it easily quenched the fire that the initial hose team could not do. So the lesson learned was when a wind-driven fire stops a hoseline advance and there is another access to the fire from a right angle, use it instead of sending a second line to back up the first attempting to advance against the wind-driven fire.

Another tactic is to shut the first line down, close the door and advance another line from the opposite direction with the wind. If the highrise, wind-driven fire cannot be extinguished by interior hose-lines and it is above the reach of the aerial or tower ladder, as a last resort, a New York High-Rise nozzle may be used to extinguish a fire from the floor below the fire or a fire curtain dropped down from the floor above to stop the wind. Fig. 10.5 The new glass and steel high- and low-rise office building has a large amount of electric cables in concealed spaces.

Polyvinyl chloride

Polyvinyl chloride (PVC) is the predominant fuel in a glass and steel building. PVC is used in furniture, computers, office equipment and insulation of electric wiring. When PVC burns, it can generate large quantities of toxic and irritating smoke, has a rapid heat release and gives off more British Thermal Units (BTUs) of heat than an equivalent amount of wood. Firefighters are told to “know the enemy” in a glass and steel building. The enemy is PVC.


According to a National Bureau of Standards report, Toxicity of the Pyrolysis and Combustible Products of Polyvinyl Chloride PVC, 1987, burning PVC gives off smoke with hydrogen chloride, benzene and carbon monoxide. Hydrogen chloride is a primary pulmonary irritant and carbon monoxide is an asphyxiate; both gases kill. The study confirms a PVC electric insulation fire as a common cause of lung injury to Firefighters. Most electric insulation fires occurring in modern glass and steel office buildings are minor incidents, but the smoke and fumes create serious lung injury. These minor fires are where Firefighters get most repeated exposure to PVC smoke products.

There was a major PVC fire involving electric insulation in 1975, in a New York Telephone company switching storage building and the PVC fire produced smoke that injured approximately 700 Firefighters. Firefighters’ pulmonary injuries were followed up for a decade and it was determined hydrogen chloride products in the smoke were responsible for pulmonary difficulties, permanent lung damage and deaths of New York City Firefighters.

The World Trade Center towers were considered glass and steel buildings and were loaded with PVC cable insulation and plastic furnishings. After the collapse and during the months of search and recovery operations, Firefighters and construction workers were exposed to many unknown toxic fumes, dusts and smoke, some of which was PVC. Now 16 years later, the FDNY health follow-up program is discovering Firefighters with lung problems, skin lesions, body cancers and other deadly health problems. Firefighters must consider minor electric insulation fires as toxic smoke producers and use breathing equipment to avoid even mild exposures to smoke.


There are three recurring fires in glass and steel buildings. They are all electric fires and involve combustible insulation:

  1. fluorescent light ballast fire
  2. utility electric closet fire and
  3. basement vault transformer fire.

Fluorescent light fixture fires are minor incidents involving the ballast of a fluorescent ceiling light fixture. The ballast of the light overheats and sometimes suffers a short circuit that ignites wire insulation. Firefighters can detect a smoldering ballast fire by a minor acrid electric cable smoke odor or by using a thermal imaging camera to identify a hot fluorescent light among the many in a suspended ceiling

chapter image Fig. 10.6  Burning polyvinyl chloride (PVC) gives off toxic smoke with hydrogen chloride, benzene and carbon monoxide.

Firefighters’ actions after locating the defective light is to turn the light switch off and at the circuit breaker, then remove the ceiling panels near the light fixture, dis-management the location of the light fixture disconnected and the need to have an electrician replace ballast. Some light ballasts before 1967 contain PCBs. PCBs now are banned and have been identified as a carcinogenic. However, this toxic substance still may be in service and used in electrical equipment, such as fluorescent light ballasts, capacitors and transformers. PCBs also were used in hydraulic fluids, heat transfer fluids, lubricants and plasticizers. Firefighters should use breathing equipment if PCBs are suspected during any electric cable fire and have fire gear cleaned back in quarters.

Utility closet fires

A more serious fire in a glass and steel building occurs in electric utility closets. These closed closets house electric cables extending from the basement to upper floors of the building. Cable fires in electric closets can be caused by arcing and overheating due to short circuits that ignite combustible cable insulation. The insulation covering the wires can be made of combustible material, such as polyvinyl chloride, rubber or paper.

The electric carried by the cables is high current and high voltage. Power must be shut off by building management before a fire can be extinguished in a closet. Until power is confirmed shut off, the strategy of Firefighters is to stand by with hose streams and protect exposures. Stop the fire from spreading out of the closet enclosure to the nearby combustibles. After the power is shut off, the burning combustible cable insulation fire is extinguished. Preferred extinguishment is with CO2 or dry chemical, but water may be used after power is confirmed off.

In a multi-story building, Firefighters must check the utility closets above and below on every floor for fire spread or possible fires ignited from the overheated cables that ignited the fire just extinguished. Wires can overheat on several floors simultaneously when there is a short circuit, giving the appearance fire has skipped floors. Before leaving the scene, check all utility closets on all floors and the cellar vault for smoke or fire.

Cellar utility room fires

chapter image Fig. 10.7  Do not use water on electric equipment.

The most serious fire in a glass and steel building occurs in a cellar electric transformer vault. This is a large room in a below-grade area where electric power for the entire building comes in from the street. A transformer is in this room and cables from the street enter the building at this point. Cellar electric transformer fires often start in the street and spread to this room.


Firefighters are called for a manhole or utility pole fire and find fire spread to the cellar electric transformer vault. The burning material in a cellar electric transformer is polyvinyl chloride rubber or paper and creates large quantities of black smoke and powerful, loud, arcing explosions that can shake a sidewalk outside. If size-up determines fire in a cellar electric transformer vault or room, Firefighters immediately must call the utility company to shut off power supply to the building; then contain the fire to the room of origin; prevent toxic smoke possibly containing PCBs and PVCs from spreading upward throughout the building.

Firefighters do not extinguish this fire; they shut the doors to the fire; wear masks; and do not vent. If there is a smoke-free stair, occupants of the building may be evacuated or they are ordered to stay in place. When possible, power fans should be used to direct smoke away from people and the building. If the building has a central air system, it must be shut down to prevent spreading toxic smoke of the transformer fire through the building.

Despite these efforts, toxic smoke and gas from the burning combustible cable will seep out of the cellar transformer so Firefighters must be protected with breathing equipment and occupants prevented from inhaling the smoke while waiting for the utility company to respond. Medical and haz-mat decontamination services should be called to the scene as a precaution. Upon completing this chapter, the news reported on August 30, 2015, an electric transformer fire in Khobar, Saudi Arabia, killed 10 and injured more than 200.

A glass and steel building battle plan:

  1. Stretch a hose-line to location of fire to protect exposures. Do not use water on electric equipment. If the fire is confined to content, extinguish it; if electric combustible insulation is burning, evacuate people from area of smoke.
  2. Call utility company to scene to have them shut power to burning electric power cable.
  3. Do not fight fire until utility company shuts power off. Direct and control smoke movement away from occupants and Firefighters with power fans, fog spray and controlled venting.
  4. All Firefighters must use self-contained breathing apparatus (SCBA) and should be monitored for contamination after the fire is under control.
chapter image Fig. 10.8  The World Trade Center glass and steel buildings collapsed on September 11, 2001.

The game-changer

The game-changer is an uncontrolled fire for more than two hours or a fire involving PVCs or PCBs. For prolonged fire, the IC must consider global collapse possibility and if PVCs or PCBs are present, the fire operation may require medical supervision of smoke injuries from PVC fumes or become a haz-mat operation with Firefighters and occupants being isolated and decontaminated.

Glass and Steel Building Battlespace Casualties:

  1. New York City, 343 FDNY members died when the WTC steel and glass buildings collapsed. National Institute of Standards and Technology (NIST) Final Report on the Collapse of the World Trade Center.
  2. FDNY WTC Health Program states 863 Firefighters with cancer certified for 9/11 treatment as result of working on the collapse site after the fire.

Chapter 11: Buildings Under Construction Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A building under construction, demolition or renovation is a half-finished or half-demolished structure and is a death trap environment. A construction/demolition battlespace is filled with many life-threatening hazards, such as explosive gases, dynamite, open elevator shafts, piles of wood lumber, flammable liquids, high winds, blocked exits, asbestos-filled areas, unprotected steel structure, unprotected floor edges, darkness, etc. This half-finished, dangerous environment does not exist in any other construction.

Besides the construction/demolition hazards, the unfinished building has none of the fire protection features of the typical building. This so-called passive fire protection--such as doors, fire partitions, enclosed stairs and exterior walls and windows--are absent. If a fire does start in an unfinished building under construction, it will spread wildly. Additionally, building construction restraints do not offer any fire-resistance stopping.

chapter image Fig. 11.1  This building under demolition had the exits blocked and caused the death of two FDNY Firefighters--Joseph Graffagnino (promoted posthumously to Lieutenant) and Robert Beddia.

A building under construction, demolition or alteration is defined as a “special occupancy” structure because of these unusual or special hazards it presents. The rates of Firefighter death per fire in this “special occupancy” battlespace is greater than the rate of Firefighter death in a completed building. (The National Fire Protection Association or NFPA reports four to eight Firefighters die per 100,000 residence and commercial building fires, whereas eight to 10 Firefighters die per 100,000 fires in special occupancy burning buildings.)

A construction/demolition site fire will spread in a way that Firefighters have never seen in burning occupied buildings. Firefighters operating at a construction site in smoke or at night have fallen down shafts, walked off a roof edge or dropped through an unprotected floor opening. The open structure can allow wind-blown fire to spread at lightning speed. Exits can be blocked, barricaded, removed or unfinished. Firefighters may not recognize the protection afforded by the normal compartmentation of a completed building until seeing a construction site fire. The following is an examination of construction/demolition site hazards.


Life hazards of construction site

During work hours, the major life hazard in a burning building under construction will be workers, a watchman making rounds or an operating engineer trapped in the cab of a hoisting crane. After working hours, Firefighters are the major life hazard. Fire during construction can involve explosion or collapse. Temporary sheds and shanties used by workers to store equipment can contain propane, gasoline and explosives. Any large fire in construction material will be hot and quickly can weaken steel columns, girders and floors that have not been protected with fire-retarding coverings. Wooden formwork supporting a freshly poured concrete floor will create uncontrolled wildfire flames and collapse tons of concrete being supported above.

Hazards of “salamanders” or space heaters

To cure concrete, you must heat it to dry out the moisture. To fully harden concrete can take 27 days. Only when the concrete is dry is it at full tensile and compressive strength, so every floor poured within the past 27 days is not fully hardened. To dry concrete during the construction process, heaters called “salamanders” are used. Heaters may be containers of red-hot coke or coal and/or propane-fired heaters.

Concrete-curing heaters are a major cause of fires in buildings under construction. They must be kept at least three feet away from combustible material. They are placed on the floor below the most recently poured concrete floor and here you find wood forms supporting the unstable, freshly poured concrete floor above. If the heater ignites the dried-out wood formwork supporting the new floor above, a major fire will occur and the wet poured concrete floor above can collapse.

On the upper floors, a wind will sweep the flames quickly across the forest-like wood forms. This wind-swept fire cannot be extinguished by Firefighters’ hose streams. Aerial master streams will be required. The flaming wind and convection currents created by burning formwork on the upper, open floors will not be stopped, so do not try to do so.

During and after a fire involving formwork, there is a serious collapse danger of the concrete floor above. This freshly poured, unstable, concrete floor that is not dried and now unsupported can collapse instantly and trigger a pancake collapse of lower floors. If there is no workman trapped in a building under construction that has a raging fire involving wooden formwork, the strategy should be controlled burning, while master streams outside the construction site protect exposures. Withdraw Firefighters from the floors beneath the fire of a building under construction, let the fire burn and protect exposures from radiated heat and wind-blown burning embers. During the fire, call a structural engineer to the scene to inspect the structure’s stabiliy before overhauling or conducting secondary search.

Hazards of tarpaulins

During the concrete-curing process when heaters are used, the outer edges of the floor are enclosed with canvas or plastic sheets to confine and conserve the heat on the floor drying out the concrete. If a fire occurs in the mass of wood formwork on the floor below, the recently poured concrete floor covered by these canvas or plastic sheets will ignite. Pieces of this flaming canvas or plastic will drop down onto the roofs of nearby buildings and ignite spot fires.

The roofs around a fire in a building under construction must be examined for fire spread before leaving the scene. In addition to the falling canvas/plastic, there will be wind-blown burning wood embers from the formwork scattered for some distance around the fire. The distance depends on the height of the building under constructon and the wind speed.


In a building under demolition where there is asbestos removal, the entire building may be encapsulated by wood plywood and plastic sheathing. The fire and smoke will be confined inside the half-demolished structure. This fire will be similar to a windowless building blaze. There will be no venting possible. Smoke and flames will be trapped inside the sealed structure. If the top of the building is sealed, the buildup of smoke will descend downward and engulf any Firefighters on the lower floors.

The strategy in a building under demolition or alteration to remove asbestos should be declared a haz-mat incident, with haz-mat units called. The structure should be the hot zone and no Firefighter should be allowed inside the contaminated hot zone. Again, the fire strategy should be a controlled burn. Firefighters should be withdrawn and decontaminated and the exposures protected.

In a building under construction, demolition, alteration or one that is vacant, the first size-up information should be to determine if there are any workers or occupants. If the building is unoccupied, the strategy should be as follows. If the fire is contained to the contents, use a hose stream fire attack. If the fire involves the structure or formwork, use a defensive fire attack with aerial streams. Withdraw Firefighters and protect exposures.

chapter image Fig. 11.2  The scaffolding, tools and bricks on a construction scaffold present a serious collapse danger.

Hazards of demolition

Partially constructed buildings present many firefighting dangers. On August 18, 2007, two New York City Firefighters died in a building under demolition. The building’s standpipe was not in working order; the stairways were sealed off, blocking the Firefighters’ exit; and large amounts of combustible material were stored in the building. The fire spread downward five floors. Because the building was undergoing asbestos removal during the demolition process, the structure was sealed. Firefighters were blinded and disoriented by toxic smoke as it was confined in this half-demolished structure. Fire and smoke normally spread upward, but in this case, it banked down on the lower floors where the Firefighters were getting ready to attack the fire. The top floors were sealed off to limit asbestos spread during demolition. Both fire and smoke spread downward. The blaze originated on the 17th floor; however, the Firefighters were killed on the 14th floor. Cause of death was asphyxiation due to smoke inhalation.

Hazards of floor collapse

The construction industry today uses two different kinds of framework for high-rise structures: structural steel and reinforced concrete. Buildings with a reinforced concrete framework most often are one monolithic structure of reinforced concrete called “cast-in-place.” By this method, tons of concrete are poured into wooden forms, creating a solid, reinforced concrete skeleton structure of floors and supporting columns. The building described at the beginning of this chapter is a cast-in-place, reinforced, concrete high-rise building.

Nationwide, cast-in-place concrete structures experience the most serious and greatest number of major fires of all buildings under construction. A fire in a structure of this type involves the wooden formwork timbers used to support the freshly poured, cast-in-place concrete. The fire spreads like lightning, requires a major fire department response to control, is extremely dangerous to Firefighters and extends to surrounding exposures.

A cast-in-place concrete building is built on the site, floor by floor. Steel reinforcing rods and wires are strategically placed inside wood forms, which act as molds to shape the poured concrete into floors and columns. When completed, the cast-in-place structure is one solid, concrete structure reinforced by steel. The hardened concrete provides the compressive strength to the structure and the steel reinforcement supplies the tensile strength to the concrete. After each floor is poured and hardened, the combustible formwork and supporting shoring are disassembled and rebuilt to receive the concrete for the next higher floor. After 10 or 20 floors of concrete are poured and dried by heaters during the cold weather, the wood used for the formwork becomes extremely dry and burns very easily and very rapidly. In some instances, workers apply an oil coating to the formwork to prevent it from sticking to the concrete.

chapter image Fig. 11.3  If the fire involves the concrete supporting formwork, use a defensive fire attack with aerial streams.

In some so-called “fast-track” construction projects, one concrete floor is poured every 48 hours. Although it takes approximately 27 days for concrete to reach its maximum strength, the high-rise building construction process cannot wait that long for each floor to harden. After 48 hours, a concrete floor, depending upon the type of concrete and the temperature, can have sufficient strength to enable the wood formwork below to be removed and reconstructed above. Even though the formwork is removed, bracing remains below the freshly poured concrete floors for support and portable steel jacks or timber columns will continue to support several floors below.

Construction engineers state that within 24 hours of pouring, the entire concrete floor can collapse on Firefighters if the wood formwork below has been destroyed by fire. In my opinion, this is an exaggeration. During construction, a floor collapse can trigger a multi-level floor collapse of the entire building under construction. The most serious floor collapse danger occurs during a fire in the formwork.

Hazards of concrete spalling

Concrete can collapse in small sections if heated by a scrap lumber fire or a temporary shed (construction shanty). During a fire when Firefighters are operating hose streams or overhauling in the fire area, chunks of concrete can collapse on top of them and cause serious head injuries. This is called concete “spalling” collapse. Concrete “spalling” describes the collapse of the outer layers of concrete, caused by the rapid heating of moisture trapped inside the concrete. The relative moisture content of concrete is greatest during the first 27 days after pouring. This outer layer of concrete, which collapses because of the rapid expansion of entrapped moisture, can be three or four inches thick, five or six square feet in area and weigh more than a hundred pounds.

Two types of concrete spalling are experienced during fires: an “explosive” spalling, which propels concrete downward with an explosive force and is accompanied by a loud noise and a “dropping” spalling, which is similar to a plaster ceiling collapse. Whether the collapse is explosive or not, a Firefighter can be killed or seriously injured if he/she is struck by the spalling concrete.


Crane collapse

Cranes collapse when they are overloaded, being moved from one location to another or when being assembled or disassembled at the construction site. When cranes are used to construct or demolish a structure, they can fail and collapse on nearby buildings. When a crane collapses, it can crush a nearby building and cause broken gas pipes and electric sparks, which quickly can ignite the crushed building, creating a fire. Firefighters then will have to fight fire and start a collapse search and rescue operation to search for survivors in the crushed exposure building. It will require collapse search and rescue and firefighting operations simultaneously.

If a fire in a building under construction is exposing a crane, the Incident Commander (IC) must consider a possible collapse. A collapse zone equal to the height of the crane must be set up. Police should be requested to close off blocks around the fire and evacuate all the nearby buildings when there is a possible crane collapse. During a fire in a building under construction or demolition where a crane is used, a worker often is trapped in the cab of the crane above the fire. Master streams should be used to protect a trapped crane operator and a secondary search of the crane may have to be conducted if the crane operator is unaccounted for after the fire is declared under control.

Hazards of formwork

Many types of fires occur at construction sites. One serious fire involves the combustible formwork used to support a cast-in-place concrete floor. In a building with this type of construction, the closely spaced four- by four-inch timbers and four- by eight-foot sheets of plywood create a heavy fire load.

The typical formwork system used to support and cast a reinforced concrete floor is as follows

The four- by four-inch timbers are used as columns, girders and beams (called “legs, stringers and ribs” by construction workers). The timbers support a platform of plywood sheets, which are prepared with steel reinforcing rods and wire. All edges around the perimeter of the building and floor openings are built up to keep the concrete from dripping off the sides. The concrete is poured into this wooden form or mold to create the floor and supporting columns.

When Firefighters respond to a fire involving wood formwork after the formwork is in place, but before the concrete has been poured, there is still a danger of formwork collapse without the concrete above. Because the four- by four-inch columns, girders and beams must be disassembled and reassembled 30 or 40 times (when each concrete floor is about to be poured), the construction workers use very few nails or connectors when assembling the formwork structure. These timbers, placed on top of each other and fitted together, will collapse progressively if one or two strategically placed columns or “legs” are destroyed by fire or removed during overhauling.

During a serious fire involving formwork, the timbers and plywood loaded with steel reinforcing rods are in danger of collapsing. Firefighters trapped beneath a burning mass of wood and wire would be difficult to rescue. For this reason, Firefighters should not remove the supporting timbers of formwork during overhaul operations. If necessary, they should consult with the construction shoring foreman to determine the structural stability of the formwork.


Any fire that occurs in wooden formwork will spread rapidly throughout the entire floor, making useless a single hose-line attack from a wooden access ladder through the elevator shaft. The only type of fire that can be extinguished successfully on such a floor is a small one, confined to the outer perimeter of the building, where the hose-line attack can be made from the windward side. If the wind suddenly changes direction, however, the flames will spread quickly along the underside of the plywood formwork ceiling, driving Firefighters off the floor.

Hazards of construction workers’ shanties/sheds

The most common fire in a building under constuction involves rubbish, the accumulation of trash, boxes and wrapping framework. This paper, cardboard and wood can build up quickly on a construction site. Rubbish must be removed daily from the construction site.

Rubbish accumulation sometimes occurs inside construction shanties or workers’ sheds. These temporary structures serve as offices, clothes-changing areas and equipment storage enclosures. Fires occur in shanties due to overloaded wiring, unprotected portable heaters and smoking materials. The fire burns undetected and spreads from one shanty to a nearby shed.

chapter image Fig. 11.4  A construction worker’s shanty is a source of fire ignition.

Firefighters should inspect these shanties for fire hazards and require the shanties to be constructed of noncombustible material. Propane, acetylene and other explosive gases may be stored in shanties. Extreme caution must be taken during a fire in a shanty. As soon as possible on arrival, inquire about the contents of the shanty. Use the reach of a hose stream to stay away from the fire, take cover behind a substantial object and use large-diameter master streams wherever possible.


Hazards of scaffolding

After all the floors and columns of a cast-in-place, reinforced concrete building are in place, the enclosure walls are built. Enclosure walls of masonry are often of panel wall design, one story in height and supported at each level by the outer edge of the concrete floor. The enclosing walls--usually brick or concrete block, masonry or stone slab–are constructed by erecting a timber scaffold around the perimeter of the structure. Workers stand on this platform to attach the enclosure wall from the outside.

The scaffolding, tools and wall materials on the scaffolding present a serious collapse danger during construction and during a fire involving the scaffolding. Scaffolding may extend beyond the outer edge of the structure and usually is constructed of heavy wood timbers. It may support large bundles of brick, wheelbarrows full of sand and mortar and heavy tools and equipment. The scaffolding is combustible. Sometimes, it is supported by wire cables suspended from aluminum beams, extending out beyond the structure several floors above.

If a fire occurs near one of the aluminum beams supporting the scaffolding or the fire involves the timber scaffolding itself, a collapse will result. Hundreds of pounds of timbers, bricks, wheelbarrows and mortar will rain down around the sides of the building, striking apparatus and Firefighters and crashing through the roofs and floors of smaller structures nearby.

Hazards of elevators and hoists

When erecting a cast-in-concrete high-rise building, construction workers build “hoists” on the outside of the structure to carry personnel and building materials to the upper stories. Those hoists built to lift equipment are designed differently from those built to lift personnel and, for this reason, construction workers are permitted to use only those hoists made for transporting personnel.

Over the years, workers have been killed and seriously injured when improperly riding material hoists. When responding to a fire 10 or 20 stories above the street, Firefighters must use the hoist designed for the workers, not the material and equipment hoist, even if a watchman or construction person in charge suggests to do so. Firefighting equipment may be sent to the upper floors by the material hoist car, but Firefighters never should ride up with it.

If two elevators are present at a construction site, the material and equipment car will be the one supported by only one or two steel cables and operated by controls at ground level. A bell system at each upper story signals the ground operator to move the car. The car has no safety brakes and if flames weaken the supporting cable during a fire, it will drop to the ground and crash into pieces.

The bell signal of the material hoist creates another hazard. Because it sounds like the low-air warning on some breathing apparatus units, the operator at street level, hearing the SCBA alarm, might mistake it for the hoist bell and move the car. A Firefighter entering or leaving the car at that moment can lose his or her balance and fall down the side of the building. For these reasons, Firefighters should ride the hoist car designed for use by construction workers; never the equipment hoist. The hoist for tranporting workers and Firefighters has operating controls inside the car and the car operator rides inside the car. Built-in safety brakes stop this personnel elevator car from falling free.


Hazards of wind-blown burning embers or “flying brands”

Fire companies arriving first at a fully developed construction or demolition fire must run an obstacle course through red-hot pieces of burning wood timbers. Burning timbers will present the Fire Chief with a major problem--a cause of fire extension to surrounding exposures. Swept along by powerful wind currents of flames and smoke, these airborne, red-hot pieces of timber will drop onto rooftops, into narrow shafts between buildings, blow into open windows and ignite grass, brush and trees. They settle on piles of rubbish, fire escape landings, window ledges and cornices, igniting window frames and sometimes spreading fire into the building. If the roofs and landing spots are noncombustible surfaces, there will be no problem, but if the roof covering is combustible, the fire can spread.

When a high-rise building under construction starts to extend above the rooftops of smaller adjoining structures, the construction company sometimes protects the skylights and lightweight roof decking from the impact of falling construction material and equipment by covering them with wooden planks. Often, the roof of a smaller building adjacent to the construction project will be completely covered with two- by eight-inch, heavy wood timbers. Though this precaution protects the roof from impact damage, it also changes the roof covering of the smaller building from noncombustible to combustible material. The combustible roof surface will be more susceptible to ignition from wind-blown burning timbers falling from the upper floors of the building under construction.

Chiefs in charge of fires where wind-blown burning embers are a problem must direct Firefighters to examine adjacent roofs. Sparks that have fallen on the rooftops or between the cracks of the protective wooden planks can result in exposure fires. In many states, the law requires a vertical standpipe system to be installed in any building under construction that rises above the seventh floor.

A construction/demolition site battle plan--small fires:

  1. A Liaison Officer should be assigned by the IC to work with the construction site safety officer to determine if any workers are in the construction area or fire location, presence of demolition explosives storage magazine, propane gas tanks, stability of raised cranes and any freshly poured concrete. Have this person escort Firefighters to the fire.
  2. Hook up pumper supply standpipe and sprinkler siamese. During the demolition process, sprinkler systems and standpipes must be kept operable as the building is taken down floor by floor. During construction, only the standpipe must be kept operable as the building rises. During an inspection visit, Firefighters should ensure this is complied with and the location of hydrants and fire department connections determined.
  3. If hose-line is required, bring four lengths of folded hose up to the floor below the fire and connect them to the vertical standpipe riser outlet.  
  4. During a fire, any variance between the top of the standpipe and the last floor constructed should be reported to the Officer in Command as soon as it is discovered. Additional hose will have to be hand-stretched to make up the difference.
  5. If the cap of the standpipe riser is left off and the top of the standpipe is open, water will flow out the top of the riser and there will never be enough pressure for an effective firefighting hose team. In some instances, the cap will be on the ground near the riser and could be screwed on before water supply arrives.
  6. During a fire, water supplied into the standpipe from a pumper may flow out of 10 or 20 open valves and into the stairway. Firefighters must be assigned to close valves on all floors before the standpipe is usable. The entire first-alarm assignment may have to be diverted from firefighting just to shut off the open valves on every floor.
  7. During such construction of a building, the one open standpipe valve overlooked is the lowest one in the basement. This valve often is open and used as a drain.
  8. Remember, the hose outlets must be closed and the outside stem and yoke (OS&Y) valve open.
  9. A fire department standpipe connection—siamese--should be clearly visible on the front or side of a construction site.

A construction/demolition site battle plan--large fires:

  1. A small, manageable fire is extinguished by portable extinguisher or hose-line. But for a large fire in formwork or workers’ shanty, set up master streams outside the construction site and extinguish the fire using high-pressure streams. Firefighters should remain out of the construction site hazard area when master streams are used in this special occupancy battlespace.
  2. No overhauling is carried out if the incompleted structure is a collapse danger. Establish a watch line until the owners arrive.
  3. Before leaving the scene, account for workers and turn over security to the site safety officer or watchman in charge.
  4. Firefighters should inspect all buildings under construction to familiarize themselves and pre-plan for a fire.

The game-changer

The game-changer is a broken or uncapped standpipe system. When a standpipe system is not maintaining water pressure, send Firefighters to the basement to check; this outlet valve often is left open for drainage. Also, send Firefighters to ensure that all outlet valves on all floors are closed. If the building is more than 150 feet high, it requires an outside stem and yoke shutoff valve to sector the standpipe. It may have been accidentally closed. Remember, the outlet valves must be closed and the OS& Y open. While this valve checking is proceeding, set up aerial equipment around the construction site as a game-changer action and if valve shutoff fails to make pipe water tight, withdraw Firefighters and workers and extinguish fire and protect exposures with master streams. Asbestos removal at a demolition site is a game-changer requiring outside operations and possible hazardous material decontamination.

Construction/Demolition Site Battlespace Casualties

New York City, Two Firefighters die, trapped in deconstruction site with exits sealed. NIOSH 2007-37

Chapter 12: Floor Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Floors are the platform on which Firefighters launch an interior hose-line attack. Without a stable floor, Firefighters cannot search or advance hose-lines. An important study conducted by the National Fire Protection Association (NFPA) examining parts of a structure that killed Firefighters during the years 1990 to 1999 discovered the following:

  1. There were 56 Firefighter fatalities from collapse.
  2. Twenty-one from floor collapse
  3. Nineteen from roof collapse
  4. Fourteen from wall collapse
  5. Two from ceiling collapse

More recently, another study conducted by the National Institute of Standards and Technology (NIST) on structure collapse and Firefighter fatalities from 1979 to 2002 discovered the following:

  1. Percentage of structure collapse occurring in residence buildings is increasing, even though incidents are decreasing overall.
  2. Instead of being killed when struck by a blunt force or object, Firefighters are being caught and trapped by fire after structure failure.
  3. The majority of collapse deaths occurred during fire attack.

So thinking about these two studies by NFPA and NIST, a Firefighter might assume the following

A collapse may occur in a residence building fire, during an interior fire attack. It may be a floor collapse and you may be caught and trapped by fire, smoke or parts of the fallen structure. Tragically, this was the case when Lieutenant Christopher Leach and Firefighter Jerry Fickes of Wilmington, Delaware, died in a first-floor collapse during a cellar fire in a townhouse on September 24, 2016. One of the Firefighters attempting to rescue Leach and Fickes after the floor collapse, senior Firefighter Ardythe Hope, was trapped and burned over 70 percent of her body. She died on December 2 from her injuries.

Firefighters must know as much as possible about the floor construction, the battlespace that is critical for successful interior fire attack. A dependable floor is required for Firefighters to launch an interior attack. They should understand the structural hierarchy necessary to support a floor and the importance of the connections of this hierarchy.


Floor beams

chapter image Fig. 12.1  Unrestrained beam end resting on a steel I-girder rotates off the support and fails more quickly than a floor beam restrained rigidly in a wall.

A floor beam can be a simple or continuous beam. A simple floor beam is a beam with its supports at both ends only. This floor will have one span--from masonry wall to masonry wall. A continuous beam is a beam that is supported at three or more points. A common continuous floor beam in a Type III ordinary or Type IV heavy timber building will have two spans--one span from a masonry support wall to girder and the other span from that girder support to the opposite masonry wall. Floors that are simple beams are buildings with 25 feet or less frontage or width because the maximum length of a wood beam is 25 or 30 feet. Floors that are continuous beams are more than 25 feet wide. So a 50-foot-wide building can have wood floors supported at the center by a girder, which is supported by a column.

A floor system of a large building such as this with bearing walls, columns, girders and floor beams has a hierarchy. Some parts of the floor support system are more important than others. For example, the most important parts of a floor hierarchy are the bearing walls and columns. Next come the girder, then the floor beams. The floor deck is the lowest part of the floor hierarchy. A floor beam and floor deck may be classified low in the hierarchy of a floor support system by an engineer. However, from a Firefighter’s point of view, the floor beams and deck are the most important parts; without them, there can be no interior firefighting.

If there is any weakness discovered in a floor deck or floor beam, Firefighters must take precautionary actions--withdraw and notify the Incident Commander (IC). For example, if the deck is crumbling, uneven, spongy or unusually springy, Firefighters must withdraw to safety or retreat to a stable part of the floor. If necessary, Firefighters can use the reach of a hose stream to extinguish a fire from a distance. A hose stream reach can be 30 or 40 feet. A fire can be extinguished in a room from a doorway using the reach of the hose stream or Firefighters withdraw and switch strategy from offensive to defensive from outside the structure.

Hierarchy floor system collapse

The term hierarchy and its importance to floor collapse first were identified during the post-fire investigation of the 1972 Boston Vendome Hotel tragedy. This burning building was six stories of ordinary construction, measuring 100 by 50 feet, with wood floor beams supported in one section of the building by a girder that was supported by a column. The foundation of the column was a bearing wall and during renovation, an opening was cut in the brick bearing wall directly below the column. After a major fire in the building burned for several hours, the bearing wall above the opening collapsed, triggering failure of a column above, causing collapse of a girder and all the floors above. The collapsing floor pushed out the walls on the exposure B side of the building. Factors involved in this collapse were the renovation mistake, the age of the 100-year-old structure, fire destruction of several floors, impact of master streams and floor vibrations from Firefighters working during overhauling. This floor collapse killed nine Boston Firefighters.

Floor beam end connections

In an ordinary constructed building, floor beams can be supported by a masonry bearing wall or a girder. A floor beam can rest on top of a masonry wall or steel girder and be unrestrained or it can be built into a pocket of a masonry wall and be restrained. If the wood floor beam ends are built into masonry and are rigidly encased/restrained beams, this is good for Firefighters conducting interior firefighting because if fire burns away the center of the floor, the beam ends restrained in the masonry wall pockets may stay in place and provide floor stability near the wall. This is the basis for instructing Firefighters to stay near a wall if the center of a floor seems unstable.

This safety precaution does not work if the floor beam ends are resting unrestrained on a masonry wall or a steel girder. This unrestrained floor beam end may rotate off the ledge or girder if the center of the floor fails.

chapter image Fig. 12.2  A floor beam encased in a brick wall makes the wall more stable.

There is another method of connecting the ends of wood floor beams to masonry walls called a “self-releasing” beam or “Fireman’s cut.” This wood floor beam end is cut on an angle so that it is designed to allow the floor beam to rotate off the support without causing collapse of supporting masonry walls. The self-releasing beam with a so-called Fireman’s cut can burn through at the center and the beam end can rotate off the support without damaging the masonry wall. This 30- or 45-degree angle Fireman’s cut should be called a building owner’s cut because this floor beam end connection may have saved lives when Firefighters fought fire from outside by allowing the floors to collapse, but not toppling walls on Firefighters outside with hose streams. However, today, Firefighters use interior attack most often and a self-releasing floor beam facilitates floor collapse more easily than a rigidly encased restrained beam without the cut.

Floor alterations

There are two dangerous floor alterations--one above and one below--that weaken floors. Several inches of masonry and terrazzo floor poured on top of a century-old, rotted floor adds tons of weight, while it enhances an old floor area. This decorative floor covering of several inches of cement, topped off with a layer of polished marble chip finish, usually is installed on the first floor to impress visitors. However, when there is a cellar fire below a terrazzo floor, this thick floor covering can conceal a floor weakness and also insulate heat from a cellar fire below, preventing Firefighters above from sensing the true seriousness of the fire. A terrazzo floor was one of the factors that led to the death of 12 FDNY Firefighters in the 23rd Street Wonder Drugstore fire, on October 17, 1966. It concealed the seriousness of a fire-weakened wood floor below it and the terrazzo insulated the heat of the fire raging below.


The other floor renovation that increases wood floor danger is the open-joist floor construction method. Open-joist construction features a wood floor with no plaster ceiling installed below it, but instead leaves the underside of a floor exposed. This type of wood floor often is found in the cellars of commercial and residence buildings. The public normally does not enter this area, so the floor underside is left unfinished without a plaster ceiling.

Open-joist construction also is used increasingly in modern residence and commercial construction on all floors as a design feature. Open-joist floor construction may look good, but Firefighters know it reduces time needed for fire to destroy a floor. A floor with a plaster or panel ceiling can resist fire for up to one hour, depending on the workmanship. Open-joist floor construction, along with the removal of a bearing wall partition, were factors in the floor collapse, June 5, 1998, which killed two FDNY Fire Officers on Atlantic Avenue, Brooklyn, New York. Firefighters must identify alterations, such as terrazzo floor tile and open-joist construction, and notify the IC.

Types of floor failure

There are three ways floors collapse during fire and kill Firefighters:

  1. A floor deck can collapse.
  2. Floor beams can collapse.
  3. Multiple floor levels can collapse.
chapter image Fig. 12.3  A Firefighter's leg can plunge through a floor deck collapse caused by an arson fire.
chapter image Fig. 12.4  Floor beam collapse due to age and abandonment.

Floor deck collapse most often occurs during an arson fire. When a person pours a flammable liquid on a floor and ignites it, the flames spread across a large part of the floor and weaken it before spreading upward to engulf the room. A normal fire starts in one isolated location, extends upward to the ceiling and spreads outward across the underside of the ceiling--not across a floor area.

In a flammable liquid arson fire, by the time Firefighters arrive, the room is in flame and the floor is badly weakened. As Firefighters advance a hose-line into the room, the fire-weakened floor deck collapses and Firefighters’ legs plunge through portions of the floor deck. Firefighters can have their lower body wedged between the floor beams and be unable to extricate themselves. This seemingly minor floor collapse can be deadly or result in major burns if the fire also is burning on the floor below the collapse.


The only safety action a Firefighter can take to prevent this floor deck collapse is to use a tool to forcefully probe the floor deck path ahead while searching. Also, if advancing a hose-line, keep one leg outstretched, testing the floor for holes and signs of crumbling deck, while keeping the body weight supported by a back leg. It must be cautioned that these actions are not foolproof; they may detect a hole, missing section of floor or a crumbling deck, but will not detect a floor beam weakness.

Floor beam collapse is the second way floors fail during fire. If the floor beams are weakened and in danger of collapse, a tool or outstretched leg cannot detect weakness. If there is any reason to suspect floor collapse, such as a slanted floor or another part of the floor missing beams, Firefighters should not advance. Instead, use the reach of the stream to avoid the floor beam section that is weakened or withdraw from the building. If there is no stable floor, Firefighters cannot conduct interior firefighting.

chapter image Fig. 12.5  Multi-level floor collapse due to fire.

The most deadly type of floor collapse is when one floor fails and causes the failure of the floors below. When there is danger of a multi-level floor collapse–such as uncontrolled fire burning on several floors, a burning vacant building, use of master streams for long periods, floor loads such as plumbing supplies, paper or textile storage or machine shops, buildings with unprotected, cast-iron columns or historic buildings–an IC should consider withdrawing forces if the fire is not extinguished quickly.

Defensive firefighting should not be conducted inside these multi-level, collapse-prone buildings. The fire must be extinguished or reduced to minor burning with the first two hose-lines or withdraw Firefighters from the burning building and set up defensive hose streams outside of a collapse danger zone.


A multi-level floor collapse often triggers an exterior wall collapse. As several floors collapse, they pile up against the inside of enclosure walls, creating lateral, outward pressure, pushing them outward.

Location Firefighters are caught and trapped

The NIST study states that after a floor collapse, Firefighters increasingly are caught and trapped in the building, instead of killed by the blunt force of the falling building. So after a collapse occurs, a rapid intervention team must determine where inside the burning building surviving Firefighters are trapped and rescue them before the fire spreads.

In a partial floor collapse, Firefighters may be on the floor that collapsed or in the collapse cavity. For example, on December 20, 1991, in Brackenridge, Pennsylvania, a first floor collapsed into the cellar, killing four Firefighters in a two-story, 75- by 75foot, Type II commercial building. Firefighters were caught and trapped on the first floor. The Firefighters did not fall into the collapse area; instead, they were caught and trapped on the first floor by a ball of fire erupting from the cellar, enveloping them after the collapse. The ball of fire, fueled from the drums of varnish paint and lacquers in the cellar, was crushed by the first-floor collapse.

In the 1966 New York City 23rd Street floor collapse, Firefighters’ bodies were found in both the cellar collapse area and on the first floor. Ten of the 12 Firefighters’ bodies were removed from the cellar where they fell when the first floor collapsed. Two Firefighters’ bodies were found on the first floor, enveloped by a ball of fire that came up from the collapse area. In this fire, there also were drums of varnish, lacquer and paint in the cellar.

So a rapid intervention rescue team must search for trapped Firefighters, both on the floor that collapses and the floor collapse area below. A victim tracking Officer must analyze the collapse area as soon as possible because the collapse may or may not shift Firefighters’ bodies. This information is given to the rapid intervention team.

For example, if the floor section falls in a “lean-to” pattern, Firefighters’ bodies shift to the bottom of the lean-to. If the floor falls in a “V”-shape, bodies will slide into the bottom of the V. In a multi-level floor, pancake collapse, Firefighters’ bodies may not shift, but drop straight down. If floors collapse in a tent shape or “A”-frame, Firefighters’ bodies may go down either side of the “A”- or tent-shape.

After a floor collapse, there may be an increase in fire spread. One of the first rescue actions must be to order a hose-line to the area where Firefighters could be trapped and extinguish fire there.

Floor collapse rescue techniques

chapter image Fig. 12.6  Terrazzo floor over wood beams may conceal a weakened supporting wood floor and insulate heat of a fire below.

The importance of fire extinguishment and simultaneous rescue were demonstrated at the 1998 Atlantic Avenue, Brooklyn, collapse. (NIOSH Firefighter Fatality Investigation #98-17) At this floor collapse, in a three-story, wood-frame, residence building, Firefighters were advancing a hose-line on the second floor when the floor suddenly collapsed, sending two Officers and three Firefighters sliding down a lean-to-shaped collapse to the first floor, along with furniture and building parts into a first-floor fire area. A mayday was transmitted and, according to the NIOSH investigation report, within three minutes, Engine 231 advanced a hose-line into the collapse area, knocked down the fire and found two of the five Firefighters in the rubble. Working under severe threat of fire, smoke and secondary collapse, other rescuers removed all Firefighters after 30 minutes. Two died; three survived.


This was a rare, successful, collapse rescue conducted, while uncontrolled fire spread. After a floor collapse when a fire is still burning, trapped Firefighters often are not saved. Here, three of five were pulled out alive. Some rescuers received burns. The strategy at this rescue was sending a hose-line quickly to knock down the fire while simultaneously conducting search and extrication operations. The success was due to the mayday signal, quick fire knockdown, a rapid intervention team and prior collapse search and rescue training. beams may conceal a weakened supporting wood floor and insulate heat of a fire below.

Wood floor stability is necessary for interior attack firefighting. A floor deck depends on the support of beams, girders, columns and bearing walls. From a firefighting point of view, terrazzo tile and open-joist floor construction are dangerous floor alterations. Rescue techniques after a floor collapse should include:

  1. Discharge hose stream down into the collapse area to wet down trapped Firefighters and quench fire. (This hose stream cools off Firefighters and lets them know others are aware of their location.)
  2. Pass a hose-line down into the floor hole to the Firefighter trapped in the collapse area.
  3. Place portable ladders into the collapse opening from above. (If Firefighters are able to move, they can escape up the ladder and out of the collapse.)
  4. Rescuers working around a partial floor collapse area must beware of a sliding floor deck effect into the opening from weakened floor sections around the perimeter of the floor.
  5. Maintain radio contact with trapped Firefighters.
  6. Dispatch a rapid intervention team to the collapse area to remove caught and trapped Firefighters. Entry from adjoining spaces is a priority.

A flooring battle plan:

chapter image Fig. 12.7  The other floor renovation that increases wood floor danger is the openjoist floor construction method. Open-joist construction features a wood floor with no plaster ceiling installed below it, but instead leaves the underside of a floor exposed.
  1. When searching in smoke, use a tool to probe the floor. Warning: This tactic will indicate holes in floors and floor deck instability, but not floor beam weakness.
  2. Use the outstretched leg and boot when advancing a hose-line to feel for holes in the floor or weakened floor boards. Again, this will detect holes or floor deck weakness, but not floor beam failure.
  3. When an unstable floor is suspected, use the reach of a hose stream and stay away from the unstable area.
  4. At first sign of a weakened floor deck or beams, withdraw from the area. Notify the IC and switch from an offensive interior attack to a defensive outside attack.
  5. Firefighters must report all floor weakness to the IC. Remember, an IC at the Command Post cannot know the structure condition of floor stability, so when Firefighters discover floor weakness, they must report it to Command. Command is depending on Firefighters inside to report dangerous floor conditions.

The game-changer

The floor game-changers are reports of a springy, spongy or terrazzo floor. An unstable or terrazzo floor report should result in a size-up of the floor below and, if necessary, result in a change of strategy. Floors are the platforms upon which we advance a hose-line. The first floor often has no ceiling and is called open-floor construction. A first floor can fail during fire more quickly when there is fire below than upper floors that have ceiling protection. If the wood beams below a terrazzo floor burn away, the terrazzo or any masonry tile floor can collapse suddenly in one large section. Terrazzo, tile or concrete floor deck insulates heat from below and conceals a fire-weakened, wood beam supporting floor.

Battlespace Floor Casualties

Ohio Captain and Firefighter killed in residence floor collapse. NIOSH 2008-09

Chapter 13: Roof Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


In New York, a Firefighter described a peaked roof collapse that killed Lieutenant Harry was "like a hangman’s trapdoor suddenly opening."Peaked roofs in outer boroughs, suburbs and rural areas are the new roof battlespace. As fire incidents in the city where flat rooftops are prevalent shift to the suburban and rural communities, where there are mostly peaked rooftops, roof operations have become more deadly. Peaked rooftops are more dangerous and difficult to operate on than flat roofs.

For example, just to get on top of a peaked roof, you need two ladders, one to climb to roof level, another to hook onto the ridge and climb up the slope. Also, a slanted roof surface can make it difficult to maintain balance while performing a firefighting function. There is no parapet around the edge of a peaked roof, so if you slip or lose your balance, you slide off the roof. Finally, sloping roofs are designed to shed water and snow, so the load-bearing capacity can be less than a flat roof. Even Firefighters who are experienced operating on flat roofs during fire must learn of the construction and hazards of peaked roofs.


Peaked roof design

chapter image Fig. 13.1  Firefighters must use a roof ladder hooked onto a ridge rafter for protection against roof deck collapse. Firefighters operate on the rungs.

There are five common, sloping peaked roofs found in suburbs and rural areas: a shed roof, a gable roof, a hip roof, a gambrel roof and a mansard roof. A shed roof has sides sloping up from two bearing walls of different heights. A gable roof has sides sloping up from two bearing walls. A hip roof has sides sloping up from four bearing walls. (A bearing wall is a wall supporting a load in addition to its own weight.) A gambrel roof has two slopes on each of two sides; the lower slope steeper than the upper. A mansard roof has two slopes; one on each of four sides; the lower slope steeper than the upper.

Each of these roofs has construction features Firefighters must know to operate effectively and safely. For example, a shed roof can have skylights flush with the roof deck and Firefighters can crash through them. A gable roof has windows on one or both gable ends that can be used to vent an attic. A hip roof has the lowest roof slope and this low angle increases risk of rafter collapse. Collar beams must tie hip roof rafters together. The lower slope of a gambrel roof is too steep to walk on and a hook ladder cannot be used to climb this steep slope. Finally, if a mansard roof collapses, it can push out the parapet supporting the lower slopes around the perimeter.

Below the roof

A difference between peaked and flat roofs is an attic space. An attic is similar to a cockloft, except that it has storage and sometimes people live there. It is a ceilng space intended to insulate the house from the hot and cold roof temperatures. An important objective of dwelling firefighting strategy is to keep the fire from extending to an attic space because if flames extend there, it usually means the entire building will be destroyed and your firefighting efforts failed.


Attic fires are difficult to extinguish for several reasons, the most important one of which is access. The opening to an attic is limited; access could be a pull-down ladder in a closet ceiling or a narrow stair. Another challenge in an attic fire is smoke removal; venting is difficult because there may be only one small attic window or it may be completely sealed. Also, an attic space may contain the largest amout of combustibles inside the building. Even if an attic is empty, there is lots of exposed wood, such as the underside of the roof deck, roof rafters, the ridge beam and unfinished wood beams and flooring.

A lower-floor fire must be kept from spreading to the attic. To do this, Firefighters must know concealed space avenues that lead to an attic from lower floors and they must check these spaces as soon as a downstair fire is extinguished. For example, any fire in a top-floor bedroom that extends to the ceiling will spread to an attic directly above. Also, if the house is balloon construction, there can be direct openings, spaces between exterior wall studs, extending from the cellar to the attic space, so any fire in a cellar can spread quickly up to the attic space. Also, it is not only the exterior walls; if there is a room or section of housing added to the building, an exterior wall can become an interior wall. Another avenue of fire spread leading up to a finished attic can be the absence of attic flooring behind an attic “knee wall.”

During any dwelling fire, an Incident Commander (IC) constantly must ask himself or herself, “Has this fire spread to the attic”? And as soon as the main fire is “knocked down,” the IC must give the order, “Have someone check the attic.”

Knee wall

An unfinished floor of an attic does not extend to the outer edges of an attic space. If the occupant decides to finish the attic and puts Sheetrock on the roof and walls to make a livable space, a so-called “knee wall” is constructed, which creates a large, concealed attic space. A knee wall is a short, knee-high partition wall built where sloping roof rafters meet the attic floor. Knee walls help create a rectangular room. A three- to six-foot-high knee wall under sloping rafters creates a concealed space that must be opened during a fire and checked for fire spread. If fire spreads to an attic, it most likely is behind the knee walls. When an IC says check the attic, these knee wall concealed spaces must be opened and checked.

Caution must be taken when Firefighters open and check a knee wall space. This space can contain built-up, super-heated smoke and fire that suddenly can erupt and quickly fill up an attic space. Firefighters opening up knee walls in attics suddenly become engulfed in smoke, disoriented and trapped while searching attics. Before a knee wall is opened, Firefighters first must size up the attic and determine an escape path.

Purlins and collar beams

Two seldom seen kinds of building construction members--purlins and collar beams—are found in attics. These wood members are used in peaked-roof construction. Purlins are horizontal beams that run perpendicular to the sloping rafters and support the roof deck. Purlins usually are found in commercial peaked roofs, supported by trusses, because here a timber truss can be spaced 15 or 20 feet apart, so purlins are needed to support the roof deck.

The other rare construction feature is a collar beam. Collar beams are designed to tie opposing roof rafters of a low slope together. Collar beams strengthen roofs by helping the sloping rafters resist the outward thrust of the rafters at the eaves. Purlins and collar beams are important for Firefighters who operate above and below peaked roofs. When above the roof, stay close to the purlin; they provide additional support for the roof deck. When below the peaked roof, do not cut or remove the collar beams because they keep the roof rafters from collapsing on top of you.


Primary structure roof members

Purlins and collar beams can be considered primary structure roof beams. Purlins support the roof deck and collar beams support roof rafters. A primary structure is a beam that supports another structure. Firefighters must be able to identify primary structure members in a peaked roof. Primary structure members should not be cut with a power saw during roof venting and they should not be pried loose during overhauling to extinguish smoldering fire. If they are destroyed by fire, precautions should be taken to shore them up before overhauling begins.

chapter image Fig. 13.2  Do not cut a primary structure member, such as a ridge rafter (beam), collar beam or plate at the eaves.

In a gable roof, primary structure members are the ridge rafter, collar beams and wood plates resting on top of bearing walls to which roof rafters are connected. The plate is an important intermediate primary structure between rafters and bearing walls. A ridge rafter connects rafters together at the peak and provides stability to the roof. When operating on a sloping peaked roof, it is advisable to stay close to the primary structures, such as the ridge rafter, because it provides additional support beneath a roof deck and can offer a high point to grab onto if you suddenly lose balance and slip down a sloping roof. Fig. 13.2 Do not cut a primary structure member, such as a ridge rafter (beam), collar beam or plate at the eaves.

Firefighters should be able to identify the location of primary structure members on other kinds of roofs besides gable roofs. For example, there are three primary structure members on a gable roof--the ridge rafter and the two plates supported by bearing walls. There can be nine primary structure members on a hip peaked roof: a ridge rafter, four plates connecting the rafters to four bearing walls and four hip rafters connecting ends of the ridge rafter to the plates at the four corners.

Roof deck construction

The fire-weakened roof deck that Lieutenant Korwatch plunged through was 80 percent unsupported of tongue and groove wood deck. The more unsupported roof deck there is, the more dangerous the peaked roof.

There are four common peaked roofs and some have more unsupported roof deck than others. For example, there are timber trusses, plank and beam, solid rafters and lightweight wood trusses. The weakest part of a roof is the roof deck, which usually is one-inch plywood or tongue and groove board between these four roof support systems. A deck is the first part of a peaked roof to be destroyed by fire and it collapses during the early stages of a fire. The more unsupported the roof deck, the more danger. For example, timber truss beams of a commercial storage peaked roof building, where Lieutenant Korwatch was killed, had 15 to 20 feet of unsupported deck area between timber truss supports.


Another roof support, such as a plank and beam, log cabin, roof system, can have five or 10 feet square feet of unsupported roof deck between the planks and beams. A typical solid rafter roof has wood deck 16 or 20 inches between roof rafters, so this roof has less unsupported roof deck area than timber truss or plank and beam.

Most flat roofs in the inner city have rafter support systems and provide the best roof deck support; not so on peaked roofs. So the best peaked roof for Firefighters is the rafter roof, which also gives a Firefighter a chance to grab onto a nearby beam if the deck fails. The worst peaked roof is one supported by lightweight wood trusses. This roof support system provides no support during a fire. In fact, a lightweight wood truss support system can be destroyed before the one-inch wood deck is destroyed.

An investigation of a fire in New York City has revealed that before the deck is destroyed, the sheet metal surface fasteners fall away and truss sections come apart. Throughout the nation, Firefighter fatalities and collapse investigations reveal lightweight truss construction peaked roofs are too dangerous to operate on when the truss structure is involved. The best strategy is: If it is just a “content fire,” use your standard procedures, but if the trusses are burning, use defensive procedures. Do not vent the roof and fight the fire from the exterior until after all occupants are removed.

Roof coverings

The construction on top of a roof deck is just as important to Firefighters as the construction below, because the roof surface can increase the chances of falling off a peaked roof. During a pre-fire plan inspection, Firefighters must check out the topside of a peaked roof. A raised aerial platform can be used to closely observe the type of sloping peaked roof covering.

Roof coverings are divided into two broad categories by the industry: built-up roof coverings and prepared roof coverings. Built-up roof coverings consist of several layers of materials applied to a roof. For example, a tar and gravel roof covering is a built-up roof. This roof covering is used on flat roofs. Prepared roof coverings, the other category, are used on peaked roofs and these materials usually are nailed to a wood roof deck.

The most common prepared roof coverings are slate, tile, wood shingle and sheet metal, which present the greatest slip and fall hazard to Firefighters operating on peaked roofs. Slate is a rock naturally found in smooth-surfaced layers. Tile shingles are pieces of unglazed fired clay. Wood shingles, used mainly on the West coast, and sheet metal roofs, used mainly on the East coast, are slippery when wet. When dried and old, roof coverings of slate, tile and wood crack under a Firefighter’s weight. An example of the hazard of slate tile cracking occurred when a Firefighter walking on slate shingles lost his balance when one tile suddenly cracked and slid out from under him. He slid down the sloping roof until the toe of one of his boots fortunately got caught in the roof gutter at the edge. Luckily, he did not fall off the roof, called for help and another Firefighter, holding onto the ridge rafter with one hand, pulled the Firefighter to safety with the other.

chapter image Fig. 13.3  Slate and tile shingle can collapse if wood under the deck is destroyed by fire. Hose streams strike the shingles or flames, heat and crack the stone.

There are several causes of slate and tile shingle becoming cracked or loose. One the connections can be destroyed by fire; hose streams striking a sloping roof can push up or break a tile section; and the roof deck to which tiles are fastened can be charred and destroyed. In some instances, a roof deck underneath can be completely destroyed by fire and, yet, slate or clay shingles remain in place and look stable and undamaged.

Unlike the above roof coverings, an asphalt roof shingle covering gives a Firefighter the best traction for walking. However, even an asphalt shingle roof is too dangerous when covered with ice, snow, moss or leaves.

Peaked roof walkability

There are some peaked roofs steeped too high to walk on, regardless of the type of shingle covering. During a pre-fire plan, the walkability of a roof should be determined and recommendations included in the fire plan.

The walkability of a sloping roof can be estimated by its pitch. A pitch of “4 in 12” indicates there are four units of roof rise to 12 units of rafter span. A “2 in 12” is a low pitch, while a “15 in 12” is an extremely high-pitched roof. A low-pitched roof, such as that on a ranch-type house, may be walked on, depending upon the type of shingle and the weather conditions. A medium-pitched roof (5 or 6 in 12) should have a roof ladder secured at the ridge or Firefighters fastened by safey harnesses. A high-pitched (slope) roof, such as that of an “A”-frame or English Tudor roof, cannot be walked on safely, even with the assistance of a roof ladder. At a high-pitched roof, a Firefighter must operate from an extended aerial ladder or while standing in the bucket of a tower ladder.

Pre-planning rooftop operations

When preparing a pre-fire plan for a building, Firefighters should identify the type of roof design, the support system and roof coverings and walkability, also showing all skylight openings. Knowledge of building construction from a pre-fire plan can greatly improve a Firefighter’s risk analysis when operating on a peaked roof.

There are limits to a pre-fire plan if the peaked roof structure is located outside the city limits or is very old. For example, in rural areas, outside city limits or zoned areas, roof construction may not conform to the local building codes and roof construction can be substandard.

chapter image Fig. 13.4  To be protected from a roof beam or ridge rafter collapse such as this, Firefighters should be supported independently by an aerial ladder or platform.

Older structures with peaked roofs built before a local building code is promulgated need not conform to code requirements. These structures, “grandfathered” into the code, also may have substandard roof construction.

Despite the danger presented by peaked roofs, there are instances where Firefighters must operate on them. For example, when there is a chimney fire and a hose-line is required or during a spreading wildfire, a Firefighter must wet down wood shingle roofs to prevent fire spread from burning embers. Finally, Firefighters may have to gain access to a roof for overhauling a smoldering shingle fire.

A rooftop battle plan:

  1. Vent top-floor windows to prevent fire from spreading through a ceiling to an attic and you may not have to operate on the roof.
  2. If necessary to cut a peaked roof, use a roof ladder hooked onto a ridge rafter for protection against sliding off the roof and in case the deck burns and collapses during an attic fire. For protection, Firefighters must walk on the ladder rungs.
  3. Use an aerial or tower ladder because they are superior to a roof ladder. Firefighters are independently supported and protected from both a roof deck and roof beam collapse during an attic fire.  
  4. During overhauling of an attic fire when you have a tongue and groove roof deck, instead of climbing on top of a high, dangerous, sloping peaked roof to
  5. You may walk on a low sloping roof and balance yourself only if the roof level is less than a 30-degree-angle rise from the ground. However, you must have a ladder regardless of the slope angle if the roof is covered with snow, ice, mildew or leaves.

The game-changer

The game-changer is truss roof construction. A truss roof, wood I-beam roof or an attic fire is a game-changer. Unless you wish to be the next IC to have Firefighters die in a truss roof collapse, change the strategy from interior attack and roof venting when the truss structure is burning, to a defensive exterior attack. Many of the residence roofs today are built with lightweight truss or wood I-beams.

Any risk manager will tell you there is too much fatal fire documentation associated with truss construction to continue interior firefighting when the structure is involved with fire. Whether lightweight truss, timber truss, open bar steel joist truss or wooden I-beam, it makes no difference. All of them have been documented to fail within five to 10 minutes.

Rooftop Battlespace Casualty

Texas Fire Officer dies after falling through collapsing gable peaked roof and becoming trapped in the attic. NIOSH 2011-26

Chapter 14: Timber Truss Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A building with a timber truss roof is a deadly battlespace for Firefighters because it comes apart quickly, gives no warning signs, causes a large-area roof collapse and, sometimes, pushes out a bearing wall. There are certain construction elements that raise a red flag in a burning building’s battlespace. A timber truss is one. It is a game-changer. Red flags must go up in an Incident Commander’s (IC’s) head at a report of a timber truss. When the flag is raised, Firefighters must be ordered to take precautions.

There is a story about the “Tragic Trilogy of Timber Truss Roof Collapse,” that Firefighters tell to describe three timber truss roof collapses that occurred in the 1960s, ‘70s and ‘80s, killing 16 New York and New Jersey Firefighters. This timber truss tragedy has three different lessons learned about how timber truss construction fails during fire. A timber truss roof, also called a long-span roof system, is a deadly battlespace that has defeated Firefighters many times.

The first part of the deadly trilogy is the account of the Cliffside Park, Cardinal Bowling Alley timber truss fire and collapse that occurred on October 16, 1967. Five Firefighters in the Ridgefield, New Jersey, Fire Department, operating on a mutual-aid call to a fire in Cliffside Park, were killed. At this fire, the bowstring timber truss roof of the bowling alley collapsed and pushed out a concrete wall, burying and killing five Ridgefield, New Jersey, Firefighters beneath concrete cinder blocks. When the roof collapsed, the Firefighters killed were operating outside the burning building.

chapter image Fig. 14.1  On August 2, 1978, six Firefighters died when a timber truss roof collapsed at Waldbaum’s Supermarket, Brooklyn, New York.

The second part of the “Tragic Trilogy of Timber Truss Roof Collapse” occurred in Brooklyn, New York. At this fire on August 2, 1978, a supermarket bowstring timber truss roof collapsed and killed six New York City Firefighters. When the bowstring truss roof collapsed, the Firefighters were working on the roof and fell through the crumbling roof into a raging fire. These Firefighters were operating on the roof of the burning building, above the fire, attempting to cut the roof and extinguish the fire with hose-lines.

The third part of this “Tragic Trilogy of Timber Truss Roof Collapse” took place in Hackensack, New Jersey. On July 1, 1988, five Firefighters operating inside a Ford auto dealership were caught and trapped by falling bowstring timber truss beams crashing through a concrete ceiling. Six Firefighters were operating a hose-line below the truss. One Firefighter, Joe Everett, escaped. Five other Firefighters were not so lucky and died inside the burning building.

The tragic trilogy shows us Firefighters are killed three different ways: operating outside when a truss pushes out a wall, operating on top of a truss roof and operating below a truss roof.

Bowstring timber truss roof collapse, number one

The Cliffside, New Jersey, Cardinal Bowling Alley building was one-story, measuring 106 by 120 feet, Type III ordinary construction, with a bowstring timber truss roof and cinder block walls. The fire, on arrival, involved a large area of the bowling alley. Soon after arrival, there was an explosion and the interior attack strategy was changed to an exterior operation and roof venting ordered. When the roof collapsed, it pushed out an enclosing wall. The falling wall killed five Firefighters from Ridgefield, New Jersey, operating a hose-line outside the building.


There could have been more deaths. When the roof collapsed, eight Firefighters were on the roof and one Firefighter fell down the slanted, collapsed roof, which opened into the fire and smoke. He was hanging onto a hose-line. Another Firefighter lowered himself, while hanging onto a broken edge of the roof and extended his leg to the trapped Firefighter, who then scrambled up his leg and body to safety. This bowstring truss roof collapsed 30 minutes after Firefighters’ arrival.

Bowstring timber truss roof collapse, number two

The Brooklyn supermarket timber truss collapse occurred in a one-story, ordinary constructed timber truss roof and brick walled building, measuring 120 by 120 feet. This timber truss was not identified during the fire. The truss attic space was enclosed by an ornamental tin ceiling; 18 inches below this ceiling was a suspended panel ceiling. The tin ceiling was attached to the bottom chords of the trusses.

On arrival, the fire was in a mezzanine--a small, intermediate landing between the first floor and ceiling. An interior firefighting strategy was launched and the visible fire in the mezzanine quickly was extinguished. No fire was visible on the first floor and mezzanine; it had spread into the truss roof space above. Reports from inside the building stated no fire spread. Reports from the roof stated heavy fire spread. This was because concealed fire traveled up into the bowstring truss attic space and spread to timber truss number five.

There were seven bowstring timber trusses supporting the roof. This truss was number five, counting from the front of the building. As the concealed fire destroyed truss number five, it collapsed and a 4,000-foot trench of roof caved in and fire roared up the roof opening. Twelve Firefighters fell into the burning crevice. Six fell into the store and survived and six other Firefighters were killed by the fire after the collapse. The truss roof collapsed 32 minutes after Firefighters’ arrival.

Bowstring timber truss collapse, number three

A Hackensack, New Jersey, building was the third part of the “Tragic Trilogy of Timber Truss Roof Collapse.” It was a one-story, with brick and timber truss roof, 224- by 175-foot, auto dealership, Type III ordinary construction. One section contained five bowstring timber trusses supporting the roof. The bowstring timber truss attic space was enclosed with a wire lath and ½-inch cement ceiling. The attic space was approximately 10 feet high and used to store auto parts. The fire occurred inside the truss attic space.

Firefighters were attempting to extinguish the fire from a ladder, operating a hoseline through a trapdoor into the attic space. Suddenly, one of the 80-foot bowstring timber trusses crashed through the ceiling above the Firefighters. Then came the others. The initial collapse trapped six Firefighters in the building. One Firefighter was able to escape; three other Firefighters were pinned beneath the falling truss roof and ceiling. Two other Firefighters retreated to a dead-end storage room, where they later were killed by the spreading fire and smoke. Five Firefighters died when the bowstring timber truss roof collapsed 36 minutes after arrival.

One lesson of the “Tragic Trilogy of Timber Truss Roof Collapse” shows three ways Firefighters can die when operating at a bowstring timber truss building fire:

  1. Firefighters can be killed operating outside a burning timber truss roof building. When a bowstring truss with sloping hip rafters collapses, it sometimes can push out a masonry wall. The falling hip rafters at each end of the bowstring roof can cause a secondary wall collapse.
  2. Firefighters operating on the roof above a burning timber truss can fall through the collapsing roof into a fire.
  3. Firefighters operating inside a burning building can be crushed and burned to death when the collapsing, long-span, timber truss falls.

The bowstring timber truss roof has more history of death and destruction in the Northeast and Midwest than on the West coast and down South. The East coast and Midwest buildings with timber truss roofs usually are old and, in some instances, suffer from neglect and improper alterations. When compared with the East coast and Midwest, the timber truss buildings in the South and West are relatively new.

The “Tragic Trilogy of Timber Truss Roof Collapse” may be the miner’s canary of the newer timber truss buildings built on the West coast and South. New timber truss buildings become old buildings and when bowstring timber trusses age and rot from lack of maintenance, they become a deadly battlespace danger. On March 8, 1998, Los Angeles Fire Captain Joseph Dupee was killed when caught and trapped by a timber truss roof collapse.


Timber truss construction

chapter image Fig. 14.2  The failure of one truss spaced 20 feet apart in a 100- by 100-foot area building collapses a roof area of 4,000 square feet.

What is a timber truss? “Timber” is wooden construction larger than two by four inches, but not large enough to be classified as heavy timber or mill construction. The “truss” is a structural composition of large wood members joined together in a group of triangles and arranged in a single plane so that loads applied at points of intersecting members will cause only direct stress (tension or compression in the members). The timbers in a truss are joined together by bolts that pass through the center of metal connectors. The most common connector is the split-ring metal connector, which is embedded in prepared depressions on the face of the timber. Its purpose is to relieve the bolts of shearing stress.

A timber truss roof can be built in a variety of shapes. There is an inclined plane truss (gable-shaped roof), a parallel chord truss (flat roof) and a bowstring truss (arch roof). The bowstring timber truss is the most common design. Its curved top chord creates an arched roof; its bottom chord is horizontal timber. Both chords outline a bow with a string attached to each end. The wooden web members connecting the top and bottom chords are of smaller dimensions; however, they are critical to the overall strength of the truss section during a fire.

When attacked by flames, the entire truss section may fail as soon as the smallest web member weakens. In other words, under fire conditions, the truss is only as strong as its weakest member. Truss construction is the most dangerous roof system that a Firefighter will encounter. It is known to collapse during the early stages of a fire and it often will cause the subsequent collapse of the front masonry enclosure wall of the structure.

In the Bronx, New York, two bowstring truss roofs collapsed. At each fire, when the truss roof fell, it caused the collapse of the front masonry wall. A close examination of both collapsed structures revealed that the front wall that failed had received--rigidly cemented in a recessed pocket--the ends of roof joists, which had sloped down from the top chord of the front truss section. These (hip rafters) joist ends did not have self-releasing fire cuts. As the ends of the roof joists resting on the upper chord of the front truss went down with the collapsing roof, the ends of the joists rigidly held in the front wall were forced up and outward. These joists acted as levers, toppling the upper portion of the front wall out into the street.

A bowstring truss roof has four bearing walls. The ends of the truss sections are supported by the side walls. The front and rear walls support the sloping hip rafter or roof joists extending from the front and rear truss sections. The question arises: Why don’t the rear walls collapse as the front walls do? One reason the rear walls did not collapse at the Bronx fires is that they were more stable and resisted the lever action of the falling roof joists. The rear walls had only a few small openings in them, while the front walls had many openings, making them less able to resist any movement of the rigidly encased, fixed, sloping roof joists. There were large openings used for trucks, double-sized windows and a normal entrance door for employees. Openings in a wall weaken its load-bearing capabilities and permit fire spread.


Size-up errors with timber truss roofs

One of the reasons Firefighters are killed by a bowstring timber truss roof collapse is that this type of roof construction gives Firefighters misleading size-up readings. Firefighters take in information they see, hear, touch and smell, consciously and subconsciously, during a fire operation. They rely on this size-up information for safety and firefighting effectiveness. A building with a bowstring truss roof differs from most other structures, however, and can send a Firefighter dangerous, misleading size-up information, which can have a disastrous effect.

Parapet walls

Most textbooks and post-fire analyses of bowstring truss roof collapses state that Firefighters and Chiefs easily and quickly can identify the bowstring truss by its curved roof. This belief is not always true. A high, decorative front parapet wall can conceal the roof shape from all operating members, except those positioned on the roof. Only a Firefighter operating on a bowstring timber truss will detect the truss by the arch shape of the roof.

During a fire, early identification of a truss is the key to a safe operation. When the truss is identified early, serious injury can be avoided by a defensive strategy. A Firefighter who discovers any type of truss in a building immediately should relay this information to the Officer in command of the fire. The Firefighter should not assume that others are aware of it, no matter how obvious it may appear.

Concave underside of the arch roof

When entering a burning room or area and able to walk in an upright position (not forced to crouch because of heat banked down below the ceiling), one subconsciously may assume the fire is small. This assumption can be a deadly error in judgment in a building with a bowstring truss roof or in any room with a high ceiling. The large space created by the concave, arched underside of the bowstring truss roof acts as a “heat sink”; that is, it allows the flow of large amounts of heat and smoke upward from the fire floor below. (On February 11, 1998, two Chicago Firefighters, Pat King and Tony Lockhart, were trapped by fire spread in a large, concave, bowstring roof space inside a burning garage.)

This upward flow delays the buildup of heat and smoke at the floor, which Firefighters normally use to sense a fire's severity. If a fire occurs in an enclosed building with a flat ceiling and burns for a period of time, the smoke and heat will accumulate inside and bank down to the floor. These combustion products can prevent a Firefighter from moving more than several feet beyond the building’s front door. The same serious fire in a building with a bowstring truss roof might allow Firefighters to enter the structure, walk upright to the rear of the occupancy and become trapped under a collapsing truss roof.

Conflicting fire reports

Chief Officers who have directed fire operations in buildings with bowstring timber truss roofs tell of receiving conflicting reports from those Firefighters operating above and below a fire. The Firefighters on the roof state that the fire is severe and beyond control of the hose team operating below. The Firefighters within the building state that the fire is small and quick extinguishment will be forthcoming. The Chiefs who have operated at such fires successfully are guided by the report from above and they withdraw those working both above and below the fire.


Fuel load in the roof beams

When Firefighters first enter a bowstring truss-roofed building with a very low fire load (such as a machine shop), they may be misled into thinking there is little to burn. Smoke or a ceiling may conceal a tremendous structural fire load in the roof system. Timber trusses, roof beams, purlins and the underside of a wooden roof deck will exist high above any content at floor level. In addition, over the years, an accumulation of paint or flammable vapors from a spray process at floor level may coat the timber trusses, encouraging flame spread and smoke generation. In a timber truss building, the main fire will be in the roof structure, not in the content below.

chapter image Fig. 14.3  There is a lumberyard of fuel in a bowstring timber truss roof.

One of the criticisms at the Brooklyn supermarket post-fire investigation was there are three size-up indicators that can warn Firefighters of the presence of a truss roof in a building and they were not detected. One is a large, open space without columns. A large space without columns indicates a long-span roof support, such as a truss. Another size-up indicator of the presence of a truss roof (bowstring truss only) is a mounded or arch roof shape. If a Firefighter goes to a roof and finds a mounded arch or barrel-shaped roof surface, this could indicate a bowstring truss roof. Warning: A parrallel chord truss (flat roof) or inclined, planed (gable roof) will not be detected by the shape of the roof. And, finally, there are certain occupancies that frequently use truss construction in the roof. They are supermarkets, bowling alleys, garages, theaters, places of worship, auto dealerships, piers and armories. Fig. 14.3 There is a lumberyard of fuel in a bowstring timber truss roof.

Fire strategy for timber truss roofs

Bowstring timber truss roofs most often are found in pre-war industrial buildings, garages, lumberyards, piers, bowling alleys and supermarkets. The property is used for manufacturing and storage. Generally, the public does not enter the truss portion and employees are the only occupants. Since interior decoration is not a factor, there may not be a ceiling concealing the bowstring timber truss roof supports. When there is no ceiling, this is good for Firefighters. It assists firefighting strategy. Without a ceiling, the trusses will be visible from the floor level below. It allows early identification of the trusses from inside the structure if smoke is not excessive and the amount of truss burning and the fire spread can be evaluated. The absence of a ceiling also gives the interior hose stream an open path to extinguish any fire in a timber truss quickly.


Timber truss concealed by ceiling

A truss roof concealed by a ceiling is much more dangerous to Firefighters than a truss roof without a ceiling. All of the three bowstring timber truss roof buildings of the tragic trilogy that killed 16 Firefighters had ceilings concealing the trusses. When a a timber truss roof is concealed by a ceiling, access to the truss attic space may be from a single ladder and a ceiling trapdoor. This ladder access may be in the rear of the building or inside a small closet. This ladder will be difficult to find during a fire. During an inspection, Firefighters should locate and become familiar with the location of the access ladder to the attic space.

The chance of extinguishing a serious fire that has spread to a timber truss attic space concealed by a ceiling is slim to none. For example, the ceiling enclosing the timber trusses in the Brooklyn supermarket was ornmenetal tin attached to purlins. The purlins were solid beams that spanned the area between the bottom chords of each timber truss roof. Below the tin ceiling, there was another suspended panel ceiling.

To gain access to the fire in the attic space, Firefighters first opened the suspended ceiling with pike poles. Next, they had to pull down the ornamental tin ceiling above the suspended ceiling. When a section of the ornamental ceiling finally was opened, a look from below showed three- by eight-inch wood (purlins) beams, 16 inches on center, that extended from the bottom chord of one truss to the bottom chord of the adjoining truss. The truss was not visible from below. Even if extinguishment from below was attempted, a hose stream directed back and forth from below into the truss attic would be broken up by the purlins, rendering extinguishment minimal.

At this fire, the strategy was to place hose streams on the roof and cut the roof open, to gain access to the fire and extinguish with hose-lines. This strategy was ineffective. When the 100-foot, number five truss collapsed (20 feet on center), it opened up 4,000 square feet of roof and Firefighters fell into the burning trench. Another lesson learned at the Brooklyn supermarket fire was early identification of the truss is critical. The final FDNY report stated, “The location and extent of the fire in the truss space was not accurately defined.” Also, there can be no extinguishment of a fire in a truss attic space from above the roof.

At the Hackensack fire, the strategy was different, but just as deadly. The strategy was to extinguish the fire in the truss attic space from below. Firefighters with hose streams operated from a vertical ladder through a ceiling trapdoor. When the 80-foot timber truss, 15 feet on center, collapsed, 2,400 square feet of ceiling caved in on top of the Firefighters. They were trapped inside the burning building by the truss. Another lesson learned at this fire was there can be no extinguishment from below the burning truss through a trapdoor in the ceiling. When you consider these two timber truss roof collapses, the only strategy that can be effective when a large fire extends to a timber truss attic (concealed) space with a ceiling is to order everyone out of the building and prepare for a defensive, outside attack, using master streams and protecting the exposures. After the roof collapse, there will be a major fire column, 20 to 50 feet high, radiating a tremendous amount of heat that can spread fires to adjoining buildings.


Timber truss not concealed by a ceiling

A content fire on the floor of a garage, inside a structure with a bowstring timber truss roof, which does not have a ceiling, may spread something like this: As a content fire grows in size, flames will extend upward, igniting a timber truss and/or the underside of the roof decking. Heat and smoke then will travel along the curved underside of the roof to the highest point. Then, flames may pass through the open webbing of several trusses, involving the underside of the roof deck at the highest point of the concave roof. Fire may spread from the point of origin to some distance away, along the underside of the roof.

A secondary fire at this high point, hidden by smoke, may feed on the trusses. It may burn undetected by Firefighters extinguishing the original fire at floor level below. The fire strategy of a first-arriving engine company at a content fire in a timber truss roof building without a ceiling should be to attack the content fire directly with a large-diameter hose-line. A powerful water stream, capable of reaching a distance of 50 feet, will be needed to extinguish any content fire, such as a car or truck, that has spread into the upper portions of the trusses. This first hose-line should attack the main body of fire.

chapter image Fig. 14.4  When a truss roof has sloping hip rafters, the collapsing roof will push out a wall simultaneously.

If this first stream does not control the flames within the first few seconds of water discharge and it appears that the fire will increase and spread to the trusses, interior firefighting should be discontinued and Firefighters withdrawn. It is difficult to justify a long-duration, defensive firefighting operation inside a structure with a timber truss roof where there is no life hazard. The fire must show immediate signs of extinguishment by the first hose stream or an outside attack should be ordered for the safety of the Firefighters. After all units are withdrawn, Firefighters should anticipate collapse of the roof and a subsequent failure of one of the enclosing masonry walls. Aerial master streams should be positioned around the four sides of the building and Firefighters should be withdrawn outside the wall collapse zones.

Fire curtains

In some timber truss roof systems, the top and bottom chords and the web members are enclosed on one side by fire-retarding materials, such as wire lath and plaster or drywall plasterboard. This material will cause the truss sections to appear like curtain boards, so fire and smoke will be confined to the bay between those two truss sections directly above the fire. This fire curtain limits the fire spread between trusses.

In some buildings, fire curtains are on every other truss. If the fire is confined between fire curtains and a collapse occurs, one timber truss will fail first. This was the case at the Brooklyn supermarket fire in Brooklyn. The number 5 truss, directly above the fire and between the number 4 and 6 trusses, with fire curtains, failed. If the chords and web members are not covered with fire-retardant curtains, then fire, heat and smoke will pass through the open spaces between all of the web members and the entire truss roof will weaken and fail at once.


If the first hose-line is successful and controls the content fire at floor level or in a single timber truss and it appears that the fire will not spread, a backup, large-diameter hose-line still should be stretched into the building. This second hose-line should sweep the underside of the roof and be available to protect Firefighters if necessary. This technique will extinguish any possible secondary fire hidden behind the smoke and heat at the underside of the roof. All Firefighters operating hose-lines should stay one truss away from the fire being extinguished. Even after extinguishment, one truss could collapse during overhauling.

Roof venting

Since smoke is the main killer at fires, roof ventilation is a lifesaving tactic in an occupied building. Roof ventilation also is necessary to improve a fire environment so Firefighters can approach a fire with a hose-line for extinguishment. At an unoccupied bowstring truss roof building, however, roof ventilation may be too dangerous to risk the lives of Firefighters.

chapter image Fig. 14.5  This collapsing truss roof pushed out the wall.

At the 1967 Cardinal Bowling Alley, Cliffside Park, New Jersey, timber truss fire, when the roof collapsed, eight Firefighters were operating on the roof. Most of the Firefighters on the roof during the sudden collapse scrambled over to the parapet wall and climbed back down the ladder. One Firefighter did not and had been thrown partially down the slanting, collapsed roof into the burning, smoky interior and could not climb back up. He was calling for help and hanging onto the hose-line to keep from falling into the fire. Another Firefighter lowered himself down the slanting, collapsed roof, while clinging onto a broken edge of the roof, and extended his leg to the trapped Firefighter. The Firefighter in the collapse void grabbed the leg and body of the Firefighter and scrambled up and out of the void, with both exiting the roof safely.


Evacuating a truss roof

In a bowstring truss-roofed building where the web areas of each truss are enclosed with fire-stopping (fire curtain) and a serious fire burns in one bay between trusses, one truss is likely to fail first. In a building such as the Brooklyn supermarket, 100- by 100-foot truss sections 20 feet on center, one truss failure will open up a 4,000-square-foot section of roof (a 40- by 100-foot area).

The direction in which a Firefighter proceeds from the roof center above the failing truss is critical. If an escaping Firefighter goes 20 feet in a direction perpendicular to the failing truss and reaches the adjoining truss, he or she may be temporarily safe. However, if the movement is toward the nearest parapet wall, the Firefighter still may go down with the collapsing roof.

The same principle would apply to Firefighters inside the building, trying to get out of the path of the falling truss. Firefighters attempting the initial hose-line attack on a fire should be positioned behind a truss section next to the one involved in fire. The reach of a powerful hose stream will allow them to be out of the collapse zone of a single truss.

Attic space quick access

If there is a small fire–such as an overheated motor or electric wiring–in the truss attic space hidden by a ceiling and the access ladder to the truss attic space can be found quickly, there is a walkway in the truss attic space that a team of Firefighters with a portable extinguisher can use. The walkway in a typical, 10-foot-high, bowstring truss attic space extends through the center or highest point of each bowstring truss, from the front to the rear of the building. This walkway provides access to the truss space for maintenance.

If the ladder and access trapdoor cannot be found and the fire is small, quick access into the concealed roof space can be achieved with a triangular roof cut at the sloping ends of the roof at the front or rear of the building. A triangular cut at the center of the sloping rafters leads directly to the walkway inside the truss space. A hose stream can be directed into a truss roof area through this roof cut opening. However, if the fire is not in the content and instead involves the truss structure, the firefighting strategy should be defensive. Remove all occupants from the buildng, position aerial master streams around the four sides of the building, establish collapse zones and protect exposures.

A timber truss battle plan:

  1. If the fire in the truss building involves only autos, trucks or furnishings, the first hose-line extinguishes the fire. However, if fire involves the truss structure and cannot be extinguished by the first hose-line, the occupants should be evacuated and an exterior defensive attack should be the strategy of the first responders.
  2. During any interior operation, continuous ceiling openings should be made to ensure the fire is not spreading throughout the truss web members.  
  3. Primary venting should be windows and doors of the building. The roof should not be vented.
  4. Aerial platforms should be positioned for possible use by a master stream with ladders and apparatus placed outside a collapse zone. An IC should prepare for a large roof fire, flying brands and truss roof and wall collapse.

The game-changer

The game-changer is a report of a timber truss roof to command. The game is changed by withdrawing Firefighters from the roof and inside the burning building. If the IC receives a size-up report of a curved or mounded roof, the fire area inside is a large, open space without any supporting columns or the occupancy is a supermarket, bowling alley, garage, theater, place of worship, lumberyard, auto dealership, pier or armory, the IC must suspect a truss roof and change the game. Early identification of the truss is the key to Firefighter safety. If you see something that looks like a truss, say something.

Timber Truss Battlespace Casualties

Wisconsin Fire Officer and two Firefighters killed in bowstring roof collapse. NIOSH 2012-08

Chapter 15: Wall Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A veteran Firefighter once told me, "Kid, when you are standing outside a burning building with a hose-line, don’t be looking at the flames, look at the wall."

The flames are not coming out to get you, the wall is!” Back in the firehouse, I wondered what part of a wall I should be looking at. The following are parts of a wall you should observe.

Wall height

A Firefighter operating a hose-line in front of a burning building should look at how high the wall is because this will determine how far the wall can fall out. There are several ways a wall collapses. If the wall falls out similar to a tree in a 90-degree-angle-type collapse, it comes out its full height. And chunks of brick, lintel beams and cornice pieces can roll out farther. It also can crumble straight down in a so-called “curtain wall” collapse, similar to a curtain cut with a scissor at the top or it could break in two pieces and fall half inward and half outward in an “inward/outward”-type collapse. Firefighters cannot tell how a wall will fall, so consider the worst; a 90-degree-angle collapse where the wall falls outward the full distance.

Load-bearing wall

A Firefighter also should determine if the wall is load-bearing or non-load-bearing. A load-bearing wall supports other parts of the structure, such as floors and the roof. This fact is important because if any one of the interconnected parts fails, it could trigger progressive collapse. For example, if the floors or roof cave in, the wall in front of you could collapse. Firefighter Ken Steel, Altoona, Pennsylvania, was killed when the roof of a one-story building collapsed and pushed out the front parapet wall on top of him.


There are several ways a Firefighter can determine if the wall is load-bearing and supporting floors or the roof. One is to check the other walls and compare it to the one in front of you. In a downtown main street, land frontage is expensive, so front walls are not load-bearing. Here, side walls are often of greater dimensions than the front wall and are the load-bearing walls, which can collapse if the floors or roof fail. In a suburban or rural area, it is different. Here, land is plentiful and large lots allow a structure to be placed with the larger dimension in the front. If the front wall is of a longer dimension than the side wall, it probably is load-bearing and if floors or the roof collapse during the fire, watch out, because the front or rear walls could come down.

Another method of determining which walls are load-bearing and interconnected is to look at the peak. If the wall in front of you is parallel with the ridge rafter or peak of the roof, it is load-bearing. Look out for the bearing walls; they can come out when the floors and roof fail. When inspecting a building during construction, it is a good time to determine which walls are load-bearing and which are non-load-bearing.

A parapet

A Firefighter should look at the parapet section of the wall. A parapet wall is the top part that extends above the roofline and is the most unstable portion. A parapet section of a wall is unstable because it is freestanding and exposed to the elements on three sides: top, front and back. A freestanding wall has fewer connections to the structure. The more connections to the structure, the more stable the wall. If a wall starts to decay, the parapet section goes first. Look here for weakness. If there are hose streams operating from the other side of the building, a water blast striking the back of the parapet could collapse this freestanding parapet wall. Even if the stream is not powerful enough to collapse the wall, it could knock off a couple of coping stones in your direction.

chapter image Fig. 15.1  A Firefighter operating a hose-line in front of a burning building should look at how high the wall is because this will determine how far the wall can fall out and hit you.

Fire experience shows parapet walls are unstable and prone to collapse. They weaken from age and exposure to elements--rain, wind, snow and ice. Unlike other enclosure walls exposed from one side only, with a parapet section, the elements permeate the wall from the top, back and front. This exposure erodes mortar binding the bricks and coping stones. Firefighters operating a hose-line in the street are in danger of a parapet collapse anytime the parapet is struck by a master stream, shaken by the shock of an explosion or pushed out by an expanding steel beam heated by a fire. Keep an eye on the parapet.


Sloping hip rafters

A Firefighter should learn about the roof behind the wall if possible. If the wall is attached to a roof that has sloping hip rafters, such as a bowstring truss, a mansard roof or hip roof, this is a danger to the wall. Here, sloping roof rafters connect the roof to the wall and could push the wall out when the roof fails. As these complex roof systems--truss, mansard and hip--start to fail during a fire, the weight of the entire roof shifts to the supporting wall. The weight of the entire roof, shingles, deck and beams is transferred through the sloping rafters, creating a lateral pressure against the wall. The moving hip rafters can act as a lever and crack the masonry enclosing wall and push it into the street. Masonry walls are designed to resist compressive loads and not lateral loads transferred through sloping roof rafters.

Wall tie plates

A Firefighter should look for cast-iron or steel tie plates on a wall. Many walls are attached to the building floor by cast-iron, star-shaped plates or rectangular, one-foot-square steel plates and there is no problem with stability. This is the case when the cast-iron stars or steel plates are evenly distributed along the wall, at the same height and in equal intervals. These evenly spaced wall ties are designed to tie a non-bearing wall to the floor beams behind it. These plate connections give the wall stability because non-bearing walls need additional bracing to the structure.

However, if the plates are not evenly positioned on the wall and seem to be in a random pattern, this can indicate there is a problem; a weak and unstable wall. There is a good chance this wall with one or two plates in different locations is defective. Random, irregular plates could indicate reinforcing “turnbuckle and tie-rod assemblies,” designed to hold a damaged or unstable wall into the building structure. These random, irregular spaced plates could be securing the wall by a cable attached to a stable part of the building. Turnbuckle and tie-rod assemblies are a collapse danger sign.


Spandrel walls

chapter image Fig. 15.2  Battlespace post-traumatic stress.

A Firefighter should check the spandrel sections of a wall for signs of weakness. A spandrel section of a wall is the exterior portion of a masonry wall between the top of one window and the bottom of the windowsill above. A spandrel section of a wall is surrounded on top and bottom by window openings and these nearby openings make this part vulnerable to cracking and failure. The more openings in a wall, the weaker the wall.

During a seismic disturbance, a masonry building often will crack and break; the same goes for a fire disturbance. Firefighters must watch out for weak portions of a wall–spandrel wall sections and the parapets. An earthquake, ground-shaking and explosion or fire can affect these two vulnerable areas of a masonry wall. Spandrel sections of a wall can serve as the “miner’s canaries” and provide an early warning of collapse. A new fire hazard of spandrel walls is attachment of combustible insulation cladding on the spandrel section that can spread fire rapidly up the entire building exterior.

Lintel beam

A Firefighter should look at the support beams over windows and doorways in a wall. Beams supporting the openings of a wall are called lintel beams and can be made of wood timber, a brick arch, reinforced masonry or steel beams. If a lintel beam appears burned away, slanted, cracked or missing bricks, it could be a warning sign of wall failure. The lintel beams spanning the tops of openings carry the wall load above a window or door and transfer it across the opening and down to the foundation.

If a lintel collapses, the wall above it can collapse. When lintels crumble, they could bring down the entire wall or a smaller spandrel section of wall above it. However, you cannot be sure which one will occur. A lintel is a load-bearing wall structure, sometimes called a “primary structural member.” A primary structure member supports another structural member. Failure of a primary structure member can trigger a progressive collapse. Failure of the lintel can cause failure of the wall.

Coping stones

A Firefighter should check the top of the wall for coping or capstones. If they are loose or missing, it could indicate danger. A coping stone is placed on top of a wall to protect it from the elements. This capstone keeps rainwater and ice melting moisture from seeping downward and eroding the mortar holding bricks together. Without a coping or capstone, the top section of a wall quickly would deteriorate. This capstone can be slate, masonry, terracotta, wood or metal. The most common coping stone is in the shape of a saddle, designed to shed water on both sides. A coping stone protects the top of the wall from elements but, unfortunately, it is the first part of a wall that loses its adhesive mortar and becomes a collapse danger.

Coping stones can weigh from 10 to 50 pounds and when knocked loose, have killed and injured Firefighters. A coping stone can be knocked off a wall by improperly retracting an aerial ladder or tower ladder bucket. Any time an aerial or tower ladder is placed at a roof, before it is returned to its bedded position, it must be raised sufficiently to clear the parapet coping before retracting the upper sliding sections. If this is not done, retracting could pull a coping stone down onto the sidewalk.


A Fire Officer stopping near the entrance of a building to adjust a SCBA facepiece was killed by a falling coping stone knocked loose by a retracting ladder. At another fire incident, the Incident Commander (IC) standing at a Command Post in front of a burning building, was struck by a flying piece of coping stone knocked loose by an aerial master stream operating in the rear of a fire building. Firefighters directing ladder streams and snorkels at large fires should avoid striking the coping stones and parapets when shifting stream targets, especially when Firefighters are working in the street below. And Firefighters in the street operating around the perimeter of a building should avoid operating below aerial ladders and in the line of fire, opposite the direction of an aerial stream.

A cornice

chapter image Fig. 15.3  Big buildings collapsing on small buildings collapse small buildings.

A Firefighter should check a cornice on the front wall of a burning building for signs of fire. A cornice is a projecting decoration that crowns the top or middle of a front wall. This wood, metal or stone architectural projection is a collapse danger during a fire. Cornice decorations can run the entire length of several buildings and sometimes are called “eyebrows.” They can collapse off a wall when the connections fastening it to the building are destroyed by flame. If fire burns the wood framework connecting the cornice to the wall, the entire cornice may collapse off the building, similar to a wave.

Cornice attachments to a wall are known to collapse even when there is no fire. When the connections fail due to age, rotting or water damage, the cornice falls off the building. A falling cornice can injure people walking in the street and during a fire, injure Firefighters. A fire-retarding decorative metal or tile cornice will have a wood interior framework that provides large amounts of fuel for a concealed fire. Flame inside or behind a cornice quickly can spread fire horizontally and extend it farther into a common roof space or into another adjoining building.


A veteran Los Angeles County Firefighter, James Howe, was killed by a 60-footlong cornice that suddenly collapsed while he was operating a hose-line in front of a burning building. An investigation revealed several contributing collapse causes: fire destruction of the connections, impact of a heavy ladder placed against the building, the cornice supporting wall became unstable after a roof collapsed and a powerful master stream striking the cornice.


A Firefighter should check a wall for the presence of a canopy. A canopy is a metal or wood protective covering, extending over a loading platform or the entrance of a residence building. Wall canopies are attached for support and sometimes collapse and crush Firefighters operating below. Canopies that are designed to protect loading platforms from elements are the most dangerous because they can have a system of pulleys and railings attached to its underside, used to move heavy merchandise from the loading platform to inside the storage building.

In Chicago, 21 Firefighters were killed in a stockyard building fire when a wall collapsed on a canopy. It caused the canopy to crush the Firefighters operating below on the loading platform. And, again, in New York City, six Firefighters died at a vacant factory building fire when a wall collapsed on top of a canopy. The canopy crushed the Firefighters operating a hose-line into a window from the loading platform. At these tragedies, Firefighters killed were outside the building, beneath the canopy.

At the New York City canopy collapse where six Firefighters died, before the collapse, when the IC left the scene, he instructed the Chief Officer left in charge not to send any Firefighters back into the vacant burning building. After returning to the collapse scene, an argument ensued, with the IC stating, “I told you not to send Firefighters back into the building.” The Chief replied, “I did not send them inside; they were outside the building when the wall collapsed.” One of the tragic lessons learned at this fire is that Firefighters operating beneath a canopy must be considered operating inside a burning building. An order to withdraw from inside a burning building and fight a fire from outside must result in Firefighters being withdrawn from beneath any canopy. If the wall above collapses, so will the canopy.


A Firefighter should identify a marquee attached to the wall of a burning building and avoid operating beneath it and in front of the wall on either side of the marquee. A marquee is a heavy metal or wood advertising sign, projecting out from the wall over a sidewalk. It usually is attached to the front wall of movie and other theaters, dance halls or department stores.

A marquee can collapse and pull a wall down with it. These heavy, hollow, advertising structures, usually found on older buildings, must be maintained to prevent deterioration and collapse. Rain, snow and/or ice can accumulate in a hollow portion of a marquee. If drains are clogged, Firefighters’ hose streams can fill up the hollow of a marquee, which is why they sometimes are called “swimming pools hanging off the side of a building.”


A marquee is a cantilever beam; that is, a beam supported at one end. A cantilever structure is less stable than a simple beam--a beam supported at both ends. Firefighters operating a hose-line in front of a burning building should avoid the area under a marquee and on the sidewalk on both sides of a canopy. Firefighters must realize if the marquee collapses, it can bring the wall on both sides down with it.

Firefighters must consider the horizontal collapse zone of a wall that has a marquee attached. How much of the adjacent wall area on both sides can collapse with the marquee? Firefighters also must consider the outward collapse zone distance. How far out will the wall fall? In New York City, a marquee collapsed and killed six Firefighters. However, they were not killed by the falling marquee; they were killed by the wall adjacent to the marquee that was pulled down with the marquee. This marquee pulled 50 feet of wall on each side down with it.

A Firefighter operating a hose-line in front of a burning building should size up the wall, as the veteran Firefighter told me to do, and if discovering any hazard listed above, take one of the following safety precautions:

Increase the reach of the hose stream. The reach of a hose stream is a safety tool. It allows Firefighters to back away from a dangerous wall. The reach of a hose stream can be increased. A handheld stream has a 50-foot reach and it can be shut down and re-connected to supply a portable deluge nozzle or ladder master stream, which has a 100-foot hose stream reach. A typical ground or aerial master stream has a 100-foot hose stream reach. This action can allow a Firefighter to move farther away from a dangerous wall.

If this cannot be done, another safety tactic is to move the hose-line to the side, away from the unstable wall, in front of an adjoining building wall. This is known as flanking the fire and can be used to avoid a dangerous wall. When you flank a fire, you stand to one side, an open area or, sometimes, in front of an adjoining building and direct a hose stream from an angle. If the wall collapses, you are safe to one side.

chapter image Fig. 15.4  After floors collapse, the walls come out.

If increasing the reach of the stream or flanking the fire wall is not possible and the wall appears dangerous, Firefighters must withdraw from the collapse danger area. Establish a collapse danger zone in front of the wall. A collapse danger zone is a distance equal to the height of the wall or a distance one and one half times or twice the height of the wall. This distance is determined by the IC. If you think a force could drive the wall out, similar to an explosion, or sloping roof rafters could push a wall out farther than its height, you must be at a distance at least twice the height of the wall away or flank the fire.


Another option the Firefighter may consider when a wall collapse is possible is to direct a hose stream from above the wall. An aerial master stream can be used to raise Firefighters above a dangerous wall to direct a stream into the burning building from above. An IC may move a tower ladder into a safe position and have Firefighters direct a stream from a raised bucket above the wall. When this safety precaution is used, a Fire Officer must ensure the truck parked in the street is out of the collapse danger zone. If the wall falls on the truck and Firefighters are in a bucket or ladder near the top, they could be catapulted into the fire.

chapter image Fig. 15.5  When there is a wall collapse danger, position hose streams out of the collapse danger zone, flank the fire or use aerial streams above the dangerous wall.

Whenever there is wall collapse danger, a recommended location to park a fire apparatus around a burning building is in one of the “corner safe areas.” There are four corner safe areas around a burning building. They are at the corners of a burning building. When you look down at a burning building from a “bird’s-eye view” and imagine all four walls collapsing, there will be four corner areas with less collapse rubble in the street. These are the corner safe areas where you should position fire apparatus and from which you should operate. As one Safety Chief stated, “Your truck might be struck by some parts of a falling wall here, but you have the best chance of survival at these corner locations.”

So, in conclusion, an IC must check the walls of a burning building and if danger is seen, there are three safety actions to consider:

  1. Use the reach of the hose stream and stay out of the collapse danger zone.
  2. Flank the position hose streams to the front of adjoining buildings and stay away from the front of the dangerous wall.
  3. Direct the stream from above the dangerous wall and park the apparatus in a corner safe area.

A wall battle plan:

  1. Firefighters are the eyes and ears of the IC. If you see something about a wall you don’t like, report it to the IC. Notify your supervisor.
  2. Use the 40- to 50-foot reach of your hose stream to stay outside the collapse zone.  
  3. A collapse zone is a distance equal to one or two times the height of the wall, determined by the IC.
  4. If the wall is higher than the reach of the hose stream, flank the fire building. Take a position in front of the adjoining building away from the unstable wall.
  5. Another safety action is to switch to an aerial master stream and direct the stream from above the dangerous wall.

The game-changer

The game-changer is a report of a dangerous enclosure wall or parapet wall. When the floor starts to collapse, they can push out a wall. Walls support floors and roofs, so when they start to collapse, the walls could be next. Floor collapse is a warning sign of wall collapse because when floors collapse, broken floor beams pile up at the inside of the walls and push them out. When this happens, the game should be changed by withdrawing Firefighters away from the walls and establishing a collapse zone, using master streams positioned outside the collapse zone, in a flanking location away from the wall or use an aerial stream from above the wall with the truck parked outside the collapse zone.

Wall Collapse Battlespace Casualties

Philadelphia, Pennsylvania, Fire Officer and Firefighter killed when brick wall collapses on adjoining building they were searching. NIOSH 2012-13

Chapter 16: Ceiling Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


The first order an Incident Commander (IC) gives after extinguishing a fire is, “Check the ceiling for fire!” Firefighters must open up the ceiling above the smoldering fire with pike poles. Most ceiling fires originate as content fires and spread up to the ceiling. A fire is more likely to spread vertically up into the ceiling space than horizontally behind a wall or down below to a floor. Before the fire was extinguished, super-heated convection currents rise up and transfer heat through cracks and poke-through holes around light fixtures, radiator pipes and ceiling fans into the ceiling space. And, heat is conducted through a solid plaster ceiling. The following is battlespace information an IC must know about ceiling construction dangers and how to prevent fire from spreading to a ceiling space.

Spaces above a ceiling

When Firefighters pull ceilings, the objective is to see if fire has spread to the space above. When opening up a ceiling, Firefighters must know what’s above because the area can vary greatly and if fire spreads here, fire extinguishment can vary greatly, too.

For example, a small space above a ceiling on the lower floors of a private dwelling, called a “ceiling space,” has just the underside of the floor beam spaces above. More serious is fire spread above a top-floor ceiling into a larger space, such as an attic. Fire extinguishment in this ceiling space is more difficult.

Another large space found above a top-floor ceiling of a flat-roof building is a “cockloft space,” and, similar to an attic, fire spreading to this space—above a top floor ceiling and below the roof—can grow and destroy an entire structure.


However, a worst-case scenario is fire spreading to a “common roof space.” This space above a top-floor ceiling in a row of dwellings or stores may extend across several buildings and if fire spreads to this area, it can be catastrophic.

In modern, glass and steel commercial buildings, there is a new type of ceiling space. It can be a “plenum area,” used as an air holding space for the building HVAC system. If fire spreads to this ceiling space, it can ignite combustible cable insulation. Once again, Firefighters pulling ceilings must know the space above the ceiling can vary greatly and if fire spreads here, the fire spread also varies greatly.

Ceiling construction

Ceilings can be divided into two categories--a directly affixed ceiling and a suspended ceiling. A wood lath and plaster ceiling attached to the underside of floor or roof beams is called a direct affixed ceiling and a ceiling suspended by hangers several inches or feet below the beams is a suspended ceiling. There are many concealed spaces in ordinary and wood-constructed buildings, but the suspended ceiling is one of the largest concealed spaces and very often, the location of fire extension. A suspended ceiling on the top floor or in a strip store--sometimes called a cockloft or common roof space--creates the largest concealed space in a structure. One of the most important fire spread concerns of an IC is to prevent fire spreading to this large concealed space.

Ceiling fire spread

If fire extends to the ceiling space, it spreads differently and at different speeds, depending on the type of ceiling construction--directly affixed or suspended. A direct affixed ceiling, a plaster and wood lath ceiling, attached to roof or floor beams, allows flame to spread in the spaces between the beams. In this case, Firefighters pull the ceiling down, then a hose stream wets down the spaces between the beams. Flame and smoke only travel in the spaces parallel to the beams and channeled in one direction. This fire spread is easily extinguished with a hose stream.

chapter image Fig. 16.1  Most ceiling fires originate as content fires and spread up to the ceiling space.

A question Firefighters ask when opening up a ceiling to check for fire is, “How much of the ceiling should be pulled down”? The answer is, “Open up the ceiling until there is no charring or smoldering visible on the wood. When undamaged, clean wood is seen, stop pulling down the ceiling.”

Stopping fire spread in a suspended ceiling is more difficult because there is a large space above this ceiling and flame can spread parallel and perpendicular to the beams. If the hangers are destroyed, the ceiling can collapse. You could say flame can travel twice as fast in a suspended ceiling space than in the space above a direct, affixed ceiling.

A deadly example of rapidly spreading, suspended ceiling fire occurred at a commercial kitchen stove fire in a Boston restaurant in 2011. On arrival, fire was spreading out of a burning grease duct hood over the restaurant stove. Hidden by smoke, flame spread into the suspended ceiling, destroying the ceiling support hanger strips and causing the suspended ceiling and heavy framework to collapse, trapping Firefighters Paul Cahill and Warren Payne. Unlike a direct affixed ceiling, a fire spreading in a suspended ceiling space can spread quickly, be unseen, extend behind advancing Firefighters and, in some instances, cause a collapse.

Combustibles burning in a ceiling space

Three occupancies in which suspended ceilings most often are found are stores, renovated buildings and top floors of multiple dwellings. In addition to the large concealed space allowing fire to spread rapidly, there can be plenty of fuel in a suspended ceiling space.

Tenements can have old gas lighting fixture piping that has been plugged, but still pressurized with gas in the pipes. Even in a directly affixed ceiling of every apartment, there can be electric ceiling light fixtures next to an old gas light fixture that now is leaking gas. Gas companies plugged up the gas light pipes, but did not disconnect them.

Also, in some buildings, there can be several suspended ceilings installed, one below the other with remaining wood framing and combustible tile, creating a small lumberyard of wood in a ceiling. If fire ignites this ceiling space with multiple ceiling frameworks left in place, it will be almost impossible to open up carefully and extinguish a spreading fire.

A new fuel found in ceiling spaces of modern buildings is electric wire and cable covered with combustible insulation. Miles of wires covered with rubber, paper and plastics, such as polyvinyl chloride, create a hot, smoky fire. To make it worse, as new cable is added, workers cut the old combustible wire and leave it in place.

In addition to the large concealed space and fuel buildup in a suspended ceiling, there is always danger of a backdraft explosion. When filled with super-heated, unburned, heated smoke and gases and Firefighters start pulling down ceiling panels, fresh air enters and could cause an explosion.

Finally, fuel can get into a suspended ceiling space if an arsonist cuts a hole in the roof and pours flammable liquid into the ceiling space. When pulling top-floor or store ceilings and it appears that black smoke and fire in a form of liquid is pouring down out of a ceiling, back out. You may become engulfed in an arsonist’s flammable liquid vapors flowing downward.


Strip store suspended ceilings

Strip stores are one of the three occupancies that often have suspended ceilings. When stores change, new owners often renovate and install a new ceiling to change the look of the interior. Instead of removing the old ceiling, they frequently suspend a new ceiling below the old one, creating what is called a double-suspended ceiling.

To install a second suspended ceiling, you must make holes in the existing ceiling to run new hanger strips through it to attach the new ceiling to the beams above. Now you have two suspended ceilings and the one above has holes in it. Any fire that enters the ceiling space of the lower ceiling quickly will spread into the ceiling space above the original ceiling.

chapter image Fig. 16.2  Strip stores are one of the three occupancies that often have suspended ceilings. Renovated buildings and top floors of multiple dwellings are the other two.

To check a ceiling space for fire extension after a content fire has been extinguished in a store, Firefighters quickly must open the ceiling and if there is another ceiling above this one, it, too, must be opened to check for fire. Experience shows it is almost impossible to open up two suspended ceilings fast enough to find and cut off fire spread. Whenever Firefighters discover a double suspended ceiling space, the IC must be notified. This information will influence firefighting strategy regarding how long and how successful an interior attack will be.


Multiple dwelling suspended ceilings

chapter image Fig. 16.3  This top-floor battlespace killed FDNY Firefighter Kevin Kane when a suspended ceiling collapsed and trapped him in a burning room.

Top floors of multiple dwellings are another occupancy that has suspended ceilings. Top-floor suspended ceilings of multiple dwellings create an insulation space between the heat and cold of the rooftop and the top-floor apartments. This insulation space, unfortunately, creates a large, concealed, common roof space over all top-floor apartments in which fire can spread. Sometimes, this space is called a “cockloft.” One of the objectives of firefighting in a multiple dwelling is to keep fire from extending to this common roof space over all apartments. If fire enters the common roof space, it can destroy the entire building with fire and water damage. A top-floor fire in a multiple dwelling is more serious than a fire on a lower floor because there is a greater chance of fire spreading into this common roof space, over the entire building and possibly adjoining buildings.

Renovated building ceilings

Renovated buildings are the third occupancy where suspended ceilings are common. Older multiple dwellings have high ceilings and when renovated, these ceilings are lowered to conserve energy. Less heat and cool air are required in a space with an eight-foot-high ceiling than a 10- or 12-foot-high ceiling space.

This ceiling height change has a detrimental effect on firefighting. Where ceilings have been lowered, they change from directly affixed ceilings to suspended ceilings. Fire in a ceiling of a renovated multiple dwelling spreads faster, becomes larger and creates a ceiling framework collapse danger that a direct affixed ceiling did not have. This ceiling renovation saves energy, but it creates a cockloft-like ceiling space on every floor. To size up in a renovated apartment, pull a section of ceiling at the door to check if it’s a direct affixed or suspended ceiling.

Membrane suspended ceilings

The most common ceiling construction in the past century was a wet plaster ceiling applied on wood lath. This ceiling was a directly affixed ceiling. Today, the most common ceiling installed is a suspended “panel” ceiling, held up by thin wire hangers and a framework of plastic or metal. This ceiling is called a “membrane ceiling” and is supposed to create a fire-retarding membrane between the occupied space and the suspended ceiling space.

This panel ceiling is tested in fire laboratories and given a one-hour, fire-retarding rating. However, after installation, it often fails to stop fire for several reasons. If the suspended ceiling space above is used as an HVAC plenum air flow space and has vents in the panels that are not firestopped, fire can enter these louvered openings and spread. If a panel ceiling has recessed lighting fixtures in the panels and they do not have fire-rated, underwriter-approved assemblies, fire can spread through the light fixture. Another common fire spread avenue is a missing or improperly placed panel. Individual panels removed by workers making repairs are not replaced or are replaced improperly. When searching a fire area that has a panel ceiling and you suspect fire has spread to the concealed space, use a pike pole to push up a panel and check the space above.

One of the advantages of a panel ceiling is its lightweight framework. So, if hanger supports are destroyed by fire and the frame collapses, it will not crush Firefighters. However, the wire and bent and broken sheet metal frame pieces can entangle and prevent a Firefighter from escaping to safety.


Ceilings and party walls

There is another fire where ceilings must be opened up and the space above checked for fire spread; that is, when fire is spreading in a common roof space of a building that has a brick party wall. During a major fire, Firefighters sometimes take positions with defending hose-lines on a roof along a parapet wall, pouring water onto flames from one side to the other of the party wall. When this action is taken, an IC should order Firefighters to go below and pull the ceilings on the floor below the roof where Firefighters are standing to check the wall from below the roofline. An IC must ensure fire is not spreading beneath the roof where Firefighters are standing.

chapter image Fig. 16.4  This ceiling renovation saves energy, but it creates a cockloft-like suspended ceiling space on every floor.

When a store or dwelling has a dividing brick wall extending through a roof, the parapet section may look good: be eight inches thick, have new coping stones on top and the mortar between bricks freshly pointed. However, the condition of the wall under the roof may be very different. If you pull the ceiling below, you may find missing bricks, holes in the mortar and/or openings to run wire, air ducts and plumbing through which fire can spread.

Also, a party wall may have roof beams from both buildings embedded in the brick, back to back or side to side, with small spaces around the beams where flame can spread through the wall. Firefighters must understand “party wall” construction is not the same as “fire wall” construction. A party wall supports floor or roof beams from two adjoining buildings and is designed to save money, not to stop fire. Sometimes, it does stop fire spread, but this is not its purpose; it is an accident. Only a fire division wall is designed to stop fire.

For example, a fire division is independently supported and there are no floor or roof beams embedded in it. The National Fire Protection Association has a strict standard (NFPA 221) regarding how to build a fire division wall and it is very different from a party wall. However, even if it is a certified fire division wall, go below and pull the ceiling to check for fire spread.

Ceiling tools and techniques

A rookie Firefighter often is assigned to carry the heaviest and most cumbersome tools to a fire; that is, a 2½-gallon extinguisher and a pike pole used for pulling ceilings. A fire hook is the most common tool used for opening ceilings. A pike pole is one kind of fire hook that has a metal point tip and hook inches below. The point breaks through the ceiling and the hook pulls down the ceiling pieces.

There are several kinds of ceilings and so there are different kinds of fire hooks. In addition to a pike pole fire hook that is designed for lath and plaster ceilings, there is an “all purpose hook,” designed for pulling tin ceilings and there is a “dry wall hook,” designed for pulling plasterboard ceilings down. However, the pike pole hook is the most common ceiling fire hook used across the nation.


A rookie assigned to carry the pike pole with the extinguisher must be trained how to use a fire hook to open the different kinds of ceilings. For example, for a lath and plaster ceiling, a Firefighter standing behind the ceiling location to be opened pulls down eye shields and with hook turned parallel with the way the lath sections run, drives the point of the pike pole up through the ceiling. Then, with hook turned slightly, ¼ turn or 90 degrees, and with short, sharp, up and downward motions, moving forward, pulls sections of the lath and plaster ceiling down in front of him or her.

chapter image Fig. 16.5  This membrane ceiling will allow fire to spread to the concealed ceiling space above it through air vents, light fixtures, and improperly fastened ceiling tile.

A tin ceiling is different. It requires a different fire hook and different technique. An ornamental tin ceiling is the most difficult ceiling to open. It comes in tin sections (two by four feet) that are soldered together. When this ceiling must be opened, a Firefighter using an “all purpose hook” first must find a solder seam where the sections are connected, pulls down eye shields and, at this seam location, bangs up the tin and creates a purchase opening to grab with the hook end. Care must be taken so Firefighters do not grab the framework; just the plaster or tin ceiling beneath the framework. If not done correctly, the entire ceiling framework and ceiling could collapse.

chapter image Fig. 16.6  Fire spreading in multiple suspended ceilings is a game-changer. Notifiy the Incident Commander.

A new tool is being used to reduce damage by opening ceilings to check for fire. Fire location in a ceiling space can be detected by a thermal imaging camera. Before any ceiling is opened, a thermal imaging camera should be used to identify hot spots. If a thermal imaging camera does not detect any heat above a ceiling, the ceiling may not have to be pulled down and damage is reduced.


Preventing ceiling fire

A veteran Firefighter once told me if we extinguish the fire quickly, it will not spread up into the ceilng space. So extinguish the fire in the room and you will not have a ceiling fire. Today, you can check the ceiling space above any fire after it is extinguished and you may not have to open it. A word of caution; it is true the ceiling space directly above the hottest part of the content fire is where fire and heat likely will spread, but there are other avenues of fire spread.

For example, check the ceiling area near where radiator pipe risers penetrate a ceiling. Also, check around any electirc light fixtures or ceiling fans. These ceiling areas will have small cracks and openings where fire and heat may spread to a ceiling space. A ceiling battle plan:

  1. To prevent fire spreading to a ceiling space, extinguish the fire before it gets there.
  2. As soon as a content fire is extinguished, use pike poles to open the ceiling and check for fire extension.
  3. Open the plaster ceiling with pike poles until you do not see any charred wood.
  4. If fire is burning in the ceiling space, continue opening up until you find the perimeter and have someone go to the floor above to cut it off as you extinguish all exposed ceiling fire.
  5. When about to enter a battlespace and you suspect fire could be spreading in the ceiling spaces already and the ceiling could collapse, first make an observation hole with a pike pole at the doorway and check for fire before entering.

The game-changer

The game-changer is fire spreading in multiple suspended ceilings. When there are multiple ceilings and fire spreading in the spaces between them, notify the IC. Experience shows Firefighters cannot open up multiple suspended ceilings with pike poles and extinguish fire with hose streams from below. Fire spreading in multiple suspended ceilings must be considered a ceiling collapse danger and is a reason to switch to a defensive exterior attack.

Battlespace Ceiling Collapse Casualty

California Firefighter killed in ceiling collapse. NIOSH 2011-5

Chapter 17: Door and Window Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Opening or closing doors in a burning building can be a life or death decision. Case study #1

A Bronx, New York, Firefighter searching apartments in a smoke-filled vacant apartment house opened a hallway door and fell down an elevator shaft. Investigation reveals elevator doors open outward and apartment doors open inward. Case study #2: Queens, New York, Firefighters forced a door to an apartment, fire exploded out into the hallway, trapping a Firefighter in a dead-end hallway. Investigation reveals the door forced open could not be closed to stop fire spread. Case study #3: Manhattan, New York, fire company went above fire to search as Firefighters forced open the fire apartment door. When the door opened, flame and heat exploded out and swept up the stairs, trapping the Officer and two Firefighters. Investigation reveals fire apartment door could not be closed after forcible entry due to fire.

Doors are lifesaving barriers found attached to every room. There is no tool carried by Firefighters that can stop fire spread, but a door can do it. When searching a complex of rooms, Firefighters should identify doors that can be used to stop sudden fire if flashover occurs.


Some tactics using closed doors to stop fire spread

When coming in a window from a ladder to search an outer room, Firefighters first should close the room door to stop fire coming in, then conduct a thorough search. When forcing a door and it appears there is heavy fire, the door must be controlled by a tool, rope or gloved hand to ensure it can be quickly shut again until the hose team is ready. When a hose-line is operated at a doorway and people appear on the stairs coming down trying to pass the fire, the door must be shut to allow them to pass.

chapter image Fig. 17.1  After this door is forced open, it should be temporarily closed until the hose team is ready to advance.

However, if there is a blast of heat and smoke from the doorway driving Firefighters to the floor, instead, the decision may be to check behind the door and sweep below heat and smoke in the hall and close the door. You close the door so fresh air does not feed the fire. When the hose team has the line charged, hose flaked out and members are masked up, the door is opened again and all move in to extinguish the fire and search for victims. This is a typical, open-door/close-door decision made at every structure fire throughout America.

There are many more complex decisions Firefighters make about doors. Doors are a survival mechanism for Firefighters and occupants in a burning building. The following are important features about doors that Firefighters must understand to make good decisions.

Fire apartment door position after initial entry

Recent, full-scale fire testing has discovered that when we initially force open a door to a fire, we actually are venting the fire. The open door allows air to enter the fire area and is venting, causing the fire to grow. It now is recommended after forcing a door to a fire area, if no victim is seen, heard or reported by a credible witness and size-up of the fire indicates fire cannot be quickly extinguished with a portable fire extinguisher, the door should be closed temporarily until the hose team is ready. Once the hose team has the charged line, the door is reopened, the hose team advances in, extinguishes fire and searches for victims.


Roof bulkhead door position

Some multi-story apartment buildings have stairs to the roof going through a roof bulkhead structure. When long duration firefighting is underway on lower floors, a large amount of smoke will rise up the stair to the upper floors and accumulate on the top floor. When this happens, an Incident Commander (IC) may have to order Firefighters to open the roof bulkhead door to prevent smoke buildup in the stairway and on the top floor.

Door position when people are descending stairs

After an apartment door is opened, the hose team is ready to advance on a fire and heavy smoke flows out of the doorway, if people suddenly appear coming down the stairs, the door to the fire area should be closed until the people pass and the stair is clear of people.

The strategy for occupant survival in a Type I, fire-resistive, high-rise apartment is to stay in the apartment and let the fire department “defend in place.” Unfortunately, the American fire service has done a poor job of educating the public regarding how to survive in high-rise habitats and occupants sometimes panic and try to escape in smoke-filled halls and stairs where they die. The best chance of survival in a high-rise fire is to remain in the apartment, behind a closed door and not go out into a hallway or stair.

Door position and wind-driven fires

chapter image Fig. 17.2  At a wind-driven fire, Firefighters withdraw, the door to the hallway is closed and a hose-line advanced from a window.

When a window is vented or breaks from heat of a fire, it sometimes creates a “wind-driven or wind-impacted fire.” Wind rushes into the broken window and creates a strong, wind-driven flow of flame and heat into the building through several rooms to the interior hallway if the apartment door is open. This incoming heat and smoke blowing into the path of Firefighters advancing a hose-line will stop their progress and force a retreat. Firefighters won't be able to make forward progress against a wind-driven fire and they will be forced out of the rooms on fire and back out into the hallway.

Any visible flame coming out a door driven by wind actually is super-heated gases igniting when mixing with air in the hallway, but the flame origin is located in the back rooms. A hose stream directed at this doorway flame will have no effect. The strategy at a wind-driven fire is to close the door, notify the IC of the wind-driven fire conditions in the hallway and recommend a second hose-line be advanced or operated through the window. Before the hose stream is directed through the window, the interior Officer must ensure the hallway door is closed and the crew is out of the apartment and in a safe location.


Door position in an evacuation stair

When there are two stairs in a multi-story commercial building, sometimes the IC divides the stairs--one stair for hose-line fire attack and the other for occupant evacuation. An attack stair used by Firefighters should not be used for occupant evacuation because it may fill with smoke. A stair designated for evacuation must remain clear of smoke and so the door leading to the fire area in this stair should not be opened by Firefighters. Occupants fleeing the fire will have to open this door, but after they leave, during the firefighting operation, this door must remain closed so people on floors above may come down past the fire floor. Other doors in the evacuation stair above and below the fire may be opened, but not the door on the fire floor.

If this door is opened, it could fill up the evacuation stair with smoke and inhibit occupants on the upper floor from using it. When occupants are ordered to leave a burning commercial building where stairs have been divided for use by the IC, they should be directed to use the stair designated for evacuation.

Stair door identification

When there are two or more stairs in a building, stair doors should be identified by an alphabet letter, such as A, B, C or D, to identify the stairway enclosure and a number to identify the floor number. It is impossible to command and control a high-rise fire and order selective evacuation if the stairs are not identified with letters and floor numbers. Stair identification on the inside and outside of a door allows Firefighters to pinpoint fire locations and it helps occupants to inform the Firefighter when and where they are trapped in a stair or hallway.

For example, a Fire Officer who locates a fire on the upper floor of a high-rise building reports to the IC, “Ladder 1 to Command, fire is located on the ninth floor and recommend stretching a line from stair A and using stair B for evacuation.”

Legal locked exit doors

In some cities, it is legal to have locked exit doors in commercial building stairways. Doors can be locked from the stairway side, but must be openable from the occupancy side. This prevents illegal entry and theft by persons coming into an occupancy from a stairway. In these commercial buildings, occupants can leave the floors to escape fire, but once inside the stair enclosure, the door locks behind them and they cannot re-enter on another floor. They are locked in the stair enclosure. The only open door in this stair from the inside is at ground level, the first floor leading to the street. Because people have been trapped in these stairs, fire codes require openable re-entry doors on designated floors and other cities require electronic remote controls that open stairway doors from the lobby desk or when a smoke detector activates.

Self-closing door position

A self-closing door is designed to be in a closed position. Self-closing doors are required in multiple dwellings. Self-closing doors have spring hinges that automatically close the doors after they are opened. This so-called self-closing door is designed to limit smoke and heat entering a hallway from a fire in an apartment after the occupants flee during a fire. It also is designed to limit smoke and heat from entering an apartment when the door is opened and occupants discover a smoke-filled hallway. In both instances, the door closes by itself.


Unfortunately, some apartment dwellers disable the hinges on self-closing doors so the door does not self-close. When a door does not close after people escape a fire because they disabled the self-closing door hinges, smoke flows out to the hallway. Some hallways in high-rise multiple dwellings have a central air system that can spread smoke to hallways on several floors above and below. When you disable a smoke detector, you risk the lives of only your family. However, when you disable a self-closing door mechanism, you risk the lives of your neighbors, too.

Doors and flashover

The “elephant in the room” or unmentioned reasons why Firefighters temporarily must close doors before the hose-line is ready is the danger of flashover. Flashover is a sudden explosion of a smoke-filled room into a fully developed, roaring fire. Flashover can happen without warning and is the most deadly event during a fire. Flashover temperatures reach 1,000 to 1,200 degrees Fahrenheit and signal the end of any effective search or rescue operation and the death of any trapped victim or Firefighter searching inside the blazing room.

Important new research conducted by Underwriters Laboratories (UL) about flashover and closing doors shows a different fire growth and flashover time/temperature curve occurs at real-world fires. Firefighters must know and understand this information for survival. This research has developed a different real-world time/temperature curve from the time/temperature curve used in a controlled laboratory test. This new real-world time/temperature fire growth curve highlights the importance of an open and closed door to a fire area and shows how an open door and uncoordinated venting increase risks.

chapter image Fig. 17.3  Public hallway scorched after fire apartment self-closing device was disabled and the door left open as occupant fled fire.

In this new time/temperature curve, there are five identifiable stages to fire growth. Stage one is the growth stage. But if the fire is not discovered, the door is closed and combustion continues to burn in an enclosed structure, it uses up oxygen. When oxygen is depleted, the temperature declines and fire decays. However, when Firefighters arrive, force open a door and this open door vents the area, there is a second, more rapid and higher temperature rise and flashover may occur. Flashover can occur during this second, rapid, super-heated temperature growth stage much more quickly as it is speeded up by prior heating before the door was opened. This research warns us of a serious fire; not one handled by a portable extinguisher. After forcing a door, it should be closed temporarily and wait for the hose team. Also, window venting must be coordinated with advance of the third hose-line. (First decay, fully developed and second decay are the other stages of fire growth.)

chapter image Fig. 17.4  Shown above is a five-stage fire growth graphic for a structure fire that factors in a closed door before Firefighters arrive and an open door as Firefighters enter to search and vent. This more realistic fire growth model shows the rapid growth of a fire after Firefighters make entry into a confined fire area and vent. It also reveals the need for Firefighter entry to be accompanied by a hose stream to quench the rapid second temperature rise and flashover.


Opening a window to a fire- and smoke-filled room is another life and death decision Firefighters must make. If windows are vented too soon, fire suddenly may flash over and trap Firefighters inside searching. At some fires, window venting must be coordinated with hose-line advance or fire spreads uncontrollably. At other fires, after venting windows and discovering trapped victims, Firefighters must enter the burning room.

Windows, like doors, are another valuable firefighting tool and Firefighters must know how to use them correctly or bad things can happen. Windows can be used for venting heat and smoke, used as avenues for hose streams when the interior attack fails and for search and rescue access. The following are important guidelines for using windows at a burning building battlespace.


Window construction

The most common type of window is the double-hung window, which has a movable top and bottom sash containing glass. Sometimes, each sash has a single, large pane of glass or small sections separated by wood muntins. There is a sill at the bottom and an interior frame covering hollow voids on the top and each side of the window must be examined for hidden fire when overhauling. When Firefighters vent a window from inside, they pull down the top sash all the way to release smoke, heat and steam at the upper levels of a room. Firefighters assigned outside vent must use a pike pole to break the top and bottom glass sections to release smoke and heat.

Windows for venting

The objective of window venting is to remove smoke and heat from a structure so Firefighters can enter from the interior hallway with hose-lines and extinguish flame and search for victims. So-called “outside vent” Firefighters with tools must break windows when the hose team advances on the fire. Inside venting is carried out after a fire has been knocked down and searching is underway; outside venting must be timed with a hose-line advance.

Windows for hose streams

Windows allow hose streams to extinguish a fire when the interior hose team is unable to advance. At some fires, heat, smoke or structure barriers prevent the advancement of an interior hose and as a secondary strategy, a hose stream is directed through a window as long as it is not being directed against Firefighters inside.

Windows assist by providing extra openings for extinguishing a structure fire. Fire insurance cost can be favorably affected by the number of windows in a building that Firefighters can use to extinguish a fire, along with the building street frontage that facilitates ladder positioning, plus road access around the structure for fire apparatus mobility. Fire insurance recognizes the importance of windows for firefighting as does the fire service.

Windows for search

Windows provide Firefighters with alternate entrances for search and rescue operations when the interior access is blocked by fire, smoke or interior collapse. After a Firefighter assigned to outside venting completes the assignment and a victim is discovered inside the vented window calling for help, the window can be used for entry and rescue. Even if there is no victim, just to be sure, a Firefighter can perform a defensive search from a window by sweeping the area directly beneath the vented window with a hand or tool.

Sometimes, unconscious victims are found crumpled up on the floor directly below a window that has just been vented. When a victim is calling for help and a Firefighter assigned outside vent must enter through a window for rescue, the IC must be notified by radio. When a Firefighter enters a smoke- and heat-filled room from a window and smoke and heat are coming in a door to the room, the Firefighter should close this door first to stop the smoke and heat and then remove the victim.


Window venting

The outside window vent assignment (OV) requires Firefighters to size up the fire building and determine the approximate location of fire in building, then determine the side of the building that must be vented and get in position to vent windows with a tool. The OV Firefighter’s objective is to assist the hose-line advancement by creating portals for the release of heat, smoke and expanding steam pushed ahead by the hose stream.

chapter image Fig. 17.5  The objective of window venting is to remove smoke and heat from a structure so Firefighters can enter from the interior hallway with hose-lines.

Window venting must be coordinated with the hose team advance. Once the OV Firefighter determines the fire area and windows to be vented, there must be communications to the interior Command Officer. For example, over the radio, “Ladder OV Firefighter #1 to Engine #1, let me know when you are ready and I will take out the windows.” Not until receiving a response from the Officer should the windows be vented. “Engine #1 to OV Firefighter, start venting; we are moving in.” When this message is received, the OV Firefighter starts breaking windows to release heat, flame and smoke. Coordination of window venting is critical, because if windows are vented and the hose team is delayed due to burst hose, poor water pressure, defective hydrant, clogged strainer or broken centrifugal pump, the fire will spread uncontrollably.

Window hose stream precautions

Window hose stream operation is not a recommended procedure. It is carried out only when the normal advance through the front side or rear door cannot be accomplished. When a hose stream or master stream is directed through a window, it must be coordinated with Firefighters operating the interior hose stream. A hose stream never should be directed through a window when there are interior operations underway because it could injure Firefighters inside. Operating opposing hose streams without radio coordination can result in Firefighter burn injuries and fire spread.

Before you direct a hose stream through a window, the Officer of interior operations first must be contacted by radio and give the report that all Firefighters are in safe positions. This may take time because the Commander may have to withdraw Firefighters from the room or apartment and close the door to prevent heat and steam blowback.


Window venting sequence

Window venting from a porch roof or fire escape is difficult and dangerous. Firefighters can be trapped on porch roofs and fire escapes.

When an outside venting tactic must be carried out from a porch roof, the ladder must be placed on the upwind side of the porch roof. If the ladder is placed on the downwind side of the porch, flame and smoke from the vented windows can prevent the Firefighters’ ladder escape after venting is completed.

Also, when there are several windows that must be vented, the sequence of venting is critical. Windows must be vented in a proper sequence or fire and smoke can prevent venting of both windows. For example, if you are on the porch and vent the window upwind first, the fire and smoke coming from this vented window may prevent you from reaching the adjoining downwind window. The first window to be broken and vented by an OV Firefighter should be the downwind window, then the upwind window, working back to the porch escape ladder that has been positioned on the upwind side of the roof.

chapter image Fig. 17.6  The Firefighter has vented the window upwind first, so the fire and smoke coming from this vented window do not prevent him from reaching the downwind window and escape ladder.

When there are two windows that must be vented from a fire escape, the window farthest away from the escape ladder must be vented first. You may have to lean over the fire escape railing to do this. You must vent several windows, working back to the fire escape ladder leading to safety below.


Window venting and flashover

Flashover is defined as a sudden explosion of flame in a smoke-filled room. Flashover sometimes kills Firefighters searching for the location of a fire. Window venting sometimes causes flashover. Fire protection engineers tell us flashover occurs when heat builds up in a room. The heat is absorbed into the upper walls and ceilings, then re-radiated down into the super-heated gases and furnishings in a room, bringing them up to their auto-ignition temperatures and they suddenly burst into flame and heat.

Temperatures in a room after flashover can reach 1,000 degrees Fahrenheit. Firefighters assigned to vent windows must know if they vent windows and the hose-line is not ready to advance, air will enter the fire room, which can speed up combustion and possibly trigger flashover. Conversely, if windows are not vented until the hose team is ready to move in and extinguish the fire, the room windows and door remain closed and starved of oxygen, then combustion and heat generation required for flashover can be slowed down. Once the hose team advances on a fire, quenching the flame and cooling temperatures, and windows are being vented simultaneously, flashover is not a problem.

Wind-driven fire

Window venting that is not coordinated with the interior hose team advance also can set up conditions needed for a wind-driven fire. For example, window venting before the hose-line is operating can open up an unobstructed path for wind from the vented window to the interior hallway. Now if wind blows into the vented window and pushes heat and flame from the window to the interior hallway, it can set up a wind-driven fire in the wrong direction that even a hose stream cannot reverse.

If Firefighters in the hallway are not ready to advance with the charged hose-line and the door forced open cannot be closed, this wind-driven fire can blow back into the hallway and trigger a chaotic Firefighter bailout or, worse yet, Firefighters trapped in a dead-end hallway section. When a wind-driven fire prevents a hose-line from being advanced from the hallway, the hallway door leading to the fire must be closed to stop the heat and flame and then another hose advanced through the venting window with the wind direction.

Window overhauling

After a fire is extinguished and overhauling begins, window frames must be examined for concealed fire. There are concealed spaces around frames of a window where hidden fire can smolder and rekindle. When we vent the window, we draw heat and flame through its opening and fire can enter these voids around a window frame. If hidden fire is suspected in the window frame, it must be removed and the concealed spaces checked for fire and washed down with the hose stream.

Sash weight rope is a recurring smoldering object found inside a window frame after a fire. This rope, used to attach counterbalance metal weights to the upper and lower window sashes, is old, frayed, broken and often found smoldering inside window concealed spaces. After removing the frame around a window, a hose stream must be directed around the top and side of a window opening. This space must be examined carefully after a fire.


A door battle plan:

  • When you force open a door, you have started ventilation of the fire.
  • After you force open a door, temporarily close it until the hose team is ready to advance.
  • When serious fire is behind the door being forced open, control the door with a rope, tool or gloved hand, so it can be closed to stop fire spread to the hall.

A window battle plan:

  • Venting windows should be coordinated with the advancement of the hose-line.
  • The hose stream should not be directed into a window until it is confirmed all Firefighters have withdrawn to safety.
  • When an outside vent Firefighter enters a smoke-filled room through a window to search, notify the Officer in command and first close the door to the room to prevent flashover. Then, perform search and rescue.
  • A defensive search can be made by sweeping the area beneath a window to check for victims.

The game-changer

After forcing open a door or window and a victim is seen, heard or reported trapped inside by a credible witness, the door or window can be entered without a hose-line for protection.

Battlespace casualties

NIOSH Firefighter fatality investigation F 2004-02 and F 2007-12

Chapter 18: Topography Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Every battlespace has a topography and Firefighters must know it to operate successfully. The topography of a fire area includes a floor layout, halls, walls, windows and room configurations. Battlespace topography differs in different buildings. The term topography in this article is defined as the configuration of a fire area--interior halls, rooms and stairs.

Firefighters have been studying and using topography for years; they call it floor layouts and draw them when conducting pre-fire planning and documenting fatal fire reports. But the topography becomes most important during a fire. Firefighters start with smoke room training, then mask confidence and graduate to maze obstacle training. After this, if Firefighters not only want to survive operating blindly in smokefilled fire areas to prevent becoming lost or disoriented, but to become more efficient at search, rescue and hose-line advance, they will study topography–floor layouts of buildings in their district. Obtain or create drawings of floor layouts, practice drawing these layouts, discuss dead-end halls, window bars, gates and Firefighter traps and, most importantly, second escape routes–porches, fire escapes, secondary exits.

During the initial attack when the fire area is filled with blinding smoke, knowledge of interior layouts or topography is critical. If you do not know the layout of the smoke-filled battlespace, it increases chances of becoming disoriented due to loss of vision and you are in more danger of being caught in a flashover or falling out a window and failing to extinguish the fire. Conversely, if you know the topography, you do not need vision. You will search in smoke with more confidence, the hose-line will be advanced more quickly and you will save more lives.


I learned about the importance of battlespace topography as a new engine company Officer working with a veteran ladder company Officer. At fires, I often saw him enter a smoky apartment, locate the fire origin and relay information about topography to me as we got ready to advance the attack hose-line. As we were about to advance the line into a burning apartment, he would tap me on the shoulder, saying something like, “You have a long hallway with rooms on the right.” Or, “You got a railroad flat.” One day, I asked him, “What’s your secret? How do you always locate the fire, find the victim and know about the apartment’s layout”? He replied, “My secret is I know the inside of these buildings like the back of my hand. I study floor layouts of buildings in our district and train my Firefighters on them. We know the inside of most of the buildings in our district. When we enter a fire to search, we know the configuration of the rooms and have terminology to describe the layout to each other. Knowing how an apartment’s rooms are configured gives us great confidence and certainty when moving blindly in smoke and darkness.” This knowledge of the battlespace helps us search and, most importantly, keeps us from becoming trapped.

chapter image Fig. 18.1  If you know the inside room layout of a fire area, you will advance the hose-line more quickly and save more lives.

The following are important building features, room arrangements and some descriptive terms of interior room layouts, which can help Firefighters know and communicate about the inside of a smoke-filled fire area.



Close a door and save a life; it may be your own. We tend to overlook the value of doors. If you close a door, you can stop fire spread. A floor layout size-up should include doors to the rooms. When Firefighters enter to search a smoke-filled room from a ladder, fire escape or porch roof, they first may want to close the door to the room they are searching. It can stop fire from temporarily spreading into the room you are searching, making it safer. A closed door may prevent your search room from flashover. A closed door also can block smoke and fire spreading from another room into your search area.


A transom is a glass window above a door and is found in old tenement buildings, which can allow fire to spread room to room, even when the door is closed. A transom was designed to be open and allow air to circulate through rooms and sometimes it could provide light from one room to another. A glass transom can negate the fire cutoff protection of a closed door. During a size-up, check for a transom over a door and if it is open.

Ceiling height

High ceilings can be deadly during fire. A 12- or 15-foot-high ceiling can allow fire to spread over your head and get behind you while you do not sense it at floor level. Also, a high ceiling can allow a buildup of heated smoke, leading to a flashover. When the room flashes over at ceiling level, the sudden, radiated heat downward can prevent your escape back to an exit. High ceilings trap Firefighters, giving them a false sense of fire intensity. At floor level, it can be relatively cool; while at ceiling level, the heat is in flashover mode.

Large, open floor

chapter image Fig. 18.2  A railroad flat is a group of rooms laid out similarly to a railroad car. You go straight through an apartment, from one room into the next one.

A large, open floor area will allow a larger fire, one that is beyond control of hose-lines. In a large floor area, flames can spread more rapidly because there are no partitions to slow it down. There is a point of no return in a large open area that if passed, Firefighters cannot escape back to an exit. Fire spreads faster than Firefighters can retreat to safety of a stair enclosure.

Experts say a large floor area of more than five or 10 thousand square feet is too large to extinguish with Firefighters’ handheld hose-lines. This large floor area should be protected with automatic sprinklers. The general rule is one hand-line can extinguish 2,500 square feet and two hand-lines 5,000 square feet. Square footage greater than this area requires automatic fire protection.


Railroad flat

A railroad flat is a term used to describe a group of rooms laid out similarly to a railroad car; you go straight through an apartment, from one room into the next one. There are usually only four rooms in a typical tenement railroad flat. When searching or advancing a hoseline, you go straight ahead. However, there are usually no doors on the large openings of a railroad flat, so if windows are vented front to rear, you may set up a wind-driven fire, which traps searching Firefighters and prevents advance of a hose-line against the wind.

Long hallway rooms off to the side

Some apartment layouts are one long hallway extending from front to rear, with rooms of the apartment off to the left or right. In this kind of layout, Firefighters who enter to search or advance an attack hose-line must take care not to pass fire in one of the rooms on the left or right as they go down the hallway. In this layout, Firefighters can become trapped in the hallway if they accidentally pass a fire room and flames spread out to the hallway, blocking their escape back to the door.

Center core floor area

In some modern commercial buildings, the floor layout may be a center core floor area, with a center core wall enclosing stairs, elevators, lobbies, bathrooms, storage rooms and utility closets. Outside, the center core area is an open floor area extending 360 degrees around the core. This layout can allow a circular fire spreading around the center core, requiring Firefighters to have two hose-lines; one to attack the fire and the other to keep it from encircling them.

Dead-end spaces

chapter image Fig. 18.3  Some apartment layouts are one long hallway extending from front to rear, with rooms off to the left or right.

We usually associate dead-end spaces with hallways and corridors. A dead-end space can be the end of a hallway that extends beyond an exit doorway. Occupants and Firefighters--blinded by smoke-moving down a hallway, looking for the exit door, feeling walls, sometimes can pass the exit door and wind up in this dead-end space.

There are also rooms inside a floor layout that can be considered dead-ends. When inspecting occupancies, Firefighters must try to identify any area in which a person could become trapped when blinded by smoke.

When arriving at any fire and about to force tending from front to rear, open a door from a public hallway, size up with rooms off to the left or the public hallway and identify the exit doors right. and any dead-end spaces in which you could be trapped if the hallway suddenly fills up with smoke.

Dead-end rooms

chapter image Fig. 18.4  This center core of the floor layout contains stairs, elevators, bathrooms, HVAC shafts and electric closets.

Bathrooms and walk-in closets are considered dead-end rooms. These are where Firefighters and occupants have been found dead. During a fire when a person becomes blinded by smoke and loses his/her sense of direction, sometimes, he/she ends up in these dead-end rooms. Typically, bathrooms have only one small, high window, which may be inaccessible when heat banks down and large closets often are windowless. (Many newer homes now feature much larger windows.) These are deadly rooms for Firefighters and occupants during a smoky fire. One misstep or wrong turn and you can be trapped in one of these rooms. The official cause of death may be listed as smoke or flashover, but the unofficial cause is disorientation and entrapment in a dead-end room.



The design of a window can be deadly for Firefighters. Some windows are easy to fall out of when searching in smoke and other windows can prevent escape from a burning room to a ladder. When sizing up a room layout, window design should be examined. For example, a window with a low sill is a deadly opening, allowing Firefighters searching in blinding smoke to trip and fall out the opening.

Firefighters looking for a window after a fire is extinguished for venting with a tool or fog nozzle are in danger of falling out a window. Any window that has a sill lower than 24 inches is a fall hazard. A Firefighter advancing in smoke will slide one leg ahead, with a bent knee, feeling for a wall that is beneath the windowsill. If the windowsill is 18 inches or lower, the Firefighter’s knee will not feel any wall and can trip and fall out an open window that already has been removed for venting by an outside vent Firefighter or in a vacant building. Large, second-floor show windows with low windowsills can be deadly.

One night after extinguishing a fire in a vacant building, I went forward in the steam and smoke, looking for a window for the fog nozzle to mechanically vent the room. Moving blindly forward, knee extended, the wind direction suddenly changed and blew fresh air into the fourth-floor apartment. I found myself halfway out a large, double window with an 18-inch sill. I looked down into a dark alley.

Window guards

Children’s window guards on the lower half of a window are good for children, but bad for Firefighters. Window guards to keep children from falling out windows are common on upper floors of multiple dwellings. These metal half-window gates or bars provide safety for children, but they prevent Firefighters from a quick bailout to a ladder. Unless a Firefighter has tools and time to remove the gate, he/she can be trapped by spreading flame.


Floor level

chapter image Fig. 18.5  Standard floor plan for a center hall colonial house.

Terms such as sunken living room, duplex and split-level homes sound nice when talking of interior design, but to Firefighters, these features are bad news. A Firefighter searching or advancing a hose-line in smoke can stumble and fall and then become disoriented and trapped by fire in a layout with one of these floor design features. They are trip and stumbling hazards for Firefighters searching in smoke. When sizing up occupancies, check the floor levels.

Loss of direction caused by a stumble or fall in a room with a spreading fire can be deadly. Any change in floor level must be noted in a floor layout size-up.

Ceiling metal framework

In addition to the height of the ceiling, Firefighters must check out the type of ceiling itself and what is holding it up. With a panel ceiling, one panel can be lifted up and the support system evaluated. A suspended panel ceiling will have a metal framework for panels and thin wire hangers holding up the ceiling. If this metal and wire framework fails, it can trap Firefighters and prevent an escape from a burning room. When flames get above the ceiling, this thin wire weakens quickly, causing the ceiling’s entire framework to fall. It may not be the heavy weight of the ceiling that traps a Firefighter, but the wires and metal frame can snag and entangle him or her.

In 2000, Kimberly Smith and Lew Mayo were killed in a ceiling/roof collapse of a fast food store in Houston, Texas. Kimberly Smith had used wire cutters to try to escape.

At other ceilings, there is no suspended panel ceiling, just an exposed concrete ceiling, which is the underside of the floor above. The hazards here are different. For example, when heated by fire, heavy chunks of concrete can break away and fall. Called “concrete spalling,” it is caused by the moisture that is normally in concrete, expanding into steam when heated by fire.

The other danger of a concrete ceiling are large fluorescent light fixtures. These 10- or 20-pound ceiling light fixtures attached to a concrete ceiling are a collapse danger. They are attached to the concrete by wire screws held in place by lead anchors. The lead anchors melt easily during a fire, allowing light fixtures to fall from the ceiling. Firefighters have been injured by collapsing fluorescent light fixtures falling from concrete ceilings.


Floor openings

chapter image Fig. 18.6  If you discover a trapdoor during a topography/layout inspection, notify all first responders of this dangerous floor hazard.

Floors are the platforms Firefighters use to fight fire. Any opening in a floor must be considered deadly. Some floors have stairs leading to a cellar through a trapdoor that is flush with the floor. These so-called trapdoors are required to be closed at the end of the business day and when no one is in the cellar, but that is not always the case.

They are called trapdoors for a reason; if you fall through to the cellar, you will be trapped. Firefighters searching at night or in smoke have fallen into cellars through open trapdoors. If you discover a trapdoor during a topography/layout inspection, notify all first responders of this dangerous floor hazard.

A topography battle plan:

  1. Training sessions should include Firefighters drawing floor layouts of buildings in the response district and analyzing them. Identify key features, such as windows, halls, porch roofs, stairways to bedrooms, cellar stairs, dead-end hallway, second exits and room configuration.
  2. Obtain floor plans of tract housing being built in your response district and use them as topics in training sessions.
  3. Visit construction sites and before the building is completed, examine floor layout, open shaft ways, concealed spaces and fire protection equipment.  
  4. A pre-plan topography diagram should include: 1. Building structure--walls, rooms, windows, stairs 2. Auxiliary fire protection equipment—connections, hose outlets and area protected with sprinklers 3. Building content and exposure buildings.
  5. Topography plans should be programmed into computers and used at fires.
  6. At a fire, a quick check of the floor below gives an Officer about to advance a hose-line confidence.

The game-changer

The game-changer is a vacant building, a building under construction/demolition or renovation. There is no topography in these half-built buildings that can be depended upon. In these so-called, special occupancy buildings, the inside is changing, missing or removed. Nothing about the passive fire protection of floors, walls, ceilings or roof can be assumed in a building that is vacant, under construction/ demolition or renovation. The rate of Firefighter death is double in these so-called special occupancy buildings because there is no topography, such as floors, walls, partitions, windows and doors you can count on that will be where you expect them to be.

Topography Battlespace Casualty

Texas Fire Officer died exiting fire building after becoming disoriented and lost. NIOSH Firefighter fatality investigation F 2001-33

Chapter 19: Structure Framing Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


There is another way to study a building besides analyzing topography, combustible content, walls, floors and ceilings and that is to study the structure skeleton framework behind these surfaces. A human body has a skeleton and so does a building. The skeleton of a building consists of columns, girders, beams and load-bearing walls. This structure framing of a building is how it is all connected together.

There are different types of frames for different types of buildings and during a fire, this skeleton must be protected from fire and heat and not removed or damaged during salvage and overhauling. It would be great if Firefighters had x-ray eyes and could see the skeleton or framework of columns, girders and bearing walls holding up a structure, but we do not, so the best we can do is study building construction books, look at the exposed structure during overhauling operations or when inspecting a construction site.

Fire Officers who learn about structure skeletons of buildings from years of firefighting have an advantage when fighting fire inside a burning building battlespace. You could say they have x-ray eyes that help them evaluate stability of a structure, tell them what parts most likely will fail and where to look when attempting to evaluate a building’s stability.


This chapter examines the structure skeleton or framework of the five basic types of building construction. It also analyzes the primary structure members--walls, beams, girders and columns--and the materials they are made from--concrete, steel or wood. The more we know about a battlespace framework, the more safely and effectively we can fight fire.

Type I structure steel construction skeleton

This building is made of a skeleton framework of steel columns connected to steel girders that are supporting smaller, secondary steel beams that hold up fluted metal sheets onto which concrete is poured to make floors. The steel structure does not burn, but it can expand, warp, twist, sag and fail or cause other parts of the structure skeleton to fail.

This type structure also has a central air system of ducts and shafts as part of the structure. The ducts travel throughout the floors above suspended ceilings. In Type I steel structures, there are concealed spaces containing electric cable covered with rubber, plastic and paper insulation, which is combustible and gives off large amounts of toxic smoke. Toxic smoke from electric insulation and normal paper and plastic content of a Type I structure can be drawn into air conditioning ducts and travel several floors through an interconnected air duct system.

chapter image Fig. 19.1  Type I fire-resistive skeleton steel structure framing.

The steel structure does not add fuel to a fire, but when heated, it can fail. It can cause structure failure if the steel columns, girders or beams expand, warp, sag or buckle. Steel does not melt at a typical structure fire, but it distorts. In the New York City World Trade Center complex on 9/11, building number 7 had a steel skeleton grid structure described above. This 47-story structure suffered a global (total) collapse because of heated steel that expanded during the fire. According to the National Institute of Standards and Technology (NIST), flames from a fire heated floor beams in the northeast corner of the 13th floor, which pushed a supporting girder away from columns 79 and 44, causing failure of the entire structure skeleton.


Type I reinforced concrete structure skeleton

There are two kinds of Type I fire-resistive buildings. One is built with a steel skeleton grid and the other is built of reinforced concrete. Reinforced concrete has a concrete skeleton hardened by steel wire, cable bars and rods embedded in the concrete. This steel reinforcement gives concrete greater tensile strength.

There has been a big change in the skeleton framing of a reinforced concrete Type I fire-resistive structure. Because of this change, today’s reinforced concrete skeleton structures do not stop fire as well as the old ones. The older, pre-1960s reinforced concrete Type I structures had walls, floors and vertical stair enclosures made of concrete, brick or reinforced concrete. This is not true today.

Modern, Type I reinforced concrete buildings have less concrete and more plasterboard. Floors still may be concrete, but on each floor, apartments, stairs and compactor shafts are enclosed by thin plasterboard, not thick concrete block, which is much more difficult to penetrate.

chapter image Fig. 19.2  Type I reinforced concrete structure framing.

Also, in the older, reinforced concrete buildings, all apartments, stairs and compactor shafts enclosed in concrete block were subject to a hose stream impact test to demonstrate stability under fire conditions. At a hose stream test, the concrete wall was struck by a hose stream from a 2½-inch hose with 1⅛-inch-diameter nozzle under 50 pounds per square inch nozzle pressure. To pass the hose stream test, it could not crumble. As a result of the solid concrete skeleton frame fire in pre-1960, reinforced construction Type I concrete buildings never spread out of a compartment of origin. It was superior structure framework.


An example of modern concrete Type I construction fire resistance using thin plasterboard walls enclosing stairs, apartments and compacter chutes was demonstrated in New York City on March 22, 1987, when a fire in a cellar compactor chute of the Schomburg Plaza high-rise residence building on 110th Street and 5th Avenue spread up a compactor shaft in a 35-story reinforced concrete Type I building and broke out on the 33rd and 34th floors. Seven people on the upper floors of the building died. Three children jumped from the 33rd floor and four more were found dead in smokefilled apartments. After this fire, Firefighters lost faith in this kind of construction. The skeleton structure of a Type I reinforced concrete building has changed and no longer can be relied upon to provide the same “passive” fire protection as the older, pre-1960 structures.

Type II noncombustible/limited combustible construction structure skeleton

The framing for this type building can be masonry bearing walls supporting steel bar joist floor and roof beams, a steel grid system of columns and girders supporting steel bar joist floor and roof beams or a total steel building with steel bearing walls supporting steel bar joist floor and roof beams. The support skeleton of a Type II structure can be masonry or steel holding up steel bar joist trusses. The skeleton framework is not combustible and does not add fuel to a fire, but it fails quickly during fire. The steel in this structure is very thin and takes less heat to distort and weaken the floors and roof.

Firefighters must understand that the terms, noncombustible and fire-resistive, are not the same. A structure part may be noncombustible, yet have no ability to resist the heat of a fire. A steel structure part without fire resistance to cover it, when heated, warps, buckles, twists, bends and the building can collapse. If you want to give a piece of noncombustible steel the ability to resist fire for one or two hours of exposure, you must cover it with fire-resistive material.

chapter image Fig. 19.3  Type II noncombustible/limited combustible structure framing.

Another fact to know about noncombustible skeleton steel construction is it most often uses the steel bar joist truss for roof and floor construction. This building element is dangerous and fails quickly when heated during fire. Fire protection engineers have been telling us for years that unprotected steel bar joist trusses can fail in five to 10 minutes of fire exposure. This warning must be widely known by Firefighters because the fire service has not had any Firefighter killed by steel bar joist roof failure in the past 30 years.


The World Trade Center Towers, which collapsed on 9/11, had steel bar joist floors and this contributed to the rapid collapse of both towers, but this was a terror attack and not a normal fire. A noncombustible Type II building is designed to house a low- hazard content, one that will not develop high heat. However, if high-hazard content, such as furniture storage or woodworking manufacturing, is introduced in this kind of structure, owners must cover the steel with fire-resistive material or protect the high- hazard content with automatic sprinklers.

A recent Firefighter tragedy in a burning Type II noncombustible structure occurred in South Carolina in 2007 when fire spread rapidly in high-hazard content of a furniture showroom, overwhelming Firefighters using hand-lines to extinguish the blaze. Nine Firefighters were caught and trapped by fire in a Type II noncombustible/limited combustible building. The high-hazard content and not the bar joist truss was the cause of the Firefighter fatalities (NIOSH fatal Firefighter death investigation 2007-18).

Type III ordinary construction structure skeleton

chapter image Fig. 19.4  Type III ordinary construction structure framing.

This skeleton framework in Type III construction features brick bearing walls supporting wood floors and roof beams. Knowledge of this simple skeleton structure is important and can keep a Firefighter safe by helping him or her to identify a bearing wall and be able to distinguish it from non-bearing walls. If the ordinary Type III building has a peak roof, the bearing walls run parallel with the ridge rafter peak.

Bearing walls of buildings in inner cities where land is expensive are usually the side long walls; the short front walls are non-bearing. In suburbs and rural areas, Type III building bearing walls are often the longer front and rear walls because land is plentiful. Knowing which walls are load-bearing tells a Firefighter which walls are connected to the roof and floors and, more importantly, indicate which walls will be pushed outward if the wood roof or floors collapse.

Another important fact about the skeleton structure of a Type III ordinary constructed building is that except for the four enclosing walls, the entire interior is combustible; it is a lumberyard enclosed by four walls. Today, many structures have brick exterior veneer walls, but have wood interior frameworks. This is technically a Type IV wood-frame structure. A Type III building will have brick bearing walls, not brick veneer walls.


Type IV heavy timber skeleton structure

The skeleton structure of a Type IV heavy timber building consists of a framework of columns, girders and wood beams and this skeleton structure is exposed and not covered with plasterboard as in a Type III building. This exposed skeleton of columns, girders and beams is interconnected and when one part fails, the entire framework system can come apart.

chapter image Fig. 19.5  Type IV heavy timber structure framing.

This uncovered skeleton structure of a Type IV building adds tremendous fuel load to a fire if it burns. The large exposed timber skeleton and wood surfaces can burn hot for an extended period of time. A large fire from the exposed structure can radiate heat out windows, igniting buildings across the street and at long distances. A timber framework of columns, girders and floor beams is a fragile skeleton and connections can be unrestrained, resting on one another or connections can be tied together by simple plates and bolts that can fail during fire. When any part of the skeleton of a heavy timber building fails, there can be a global collapse of the structure, with walls and all floors pancaking down.

The greatest tragedy created by a timber building skeleton collapse of bearing walls, columns, girders

Boston, in 1972, when the burning Vendome Hotel collapsed, killing nine Firefighters. Eighteen Boston Firefighters were buried in the collapse; nine were dug out alive and nine died. The collapse cause of the skeleton framework was an illegal opening cut in a brick bearing wall, directly below a column supporting a girder and all floors above.

Type V wood construction structure skeleton

There are several skeleton structures used to build Type V wood-frame buildings. A wood building can have a framework of balloon construction, post and girt (braced frame), platform frame or lightweight wood truss. These four construction skeletons are combustible and the way they are used in framing a structure can spread fire.

Balloon construction framing can spread fire through concealed spaces on the outer walls that are between wall studs. The open spaces in the outer walls extend the entire height of the wood building in the balloon frame skeleton. The space allows fire to spread from a cellar near the foundation sill, straight up to the attic behind the knee wall, where a sloping roof meets the bearing wall. Compared to the size of the wood beams used in the flooring and roof, the two- by four-inch bearing walls are the weakest parts of a balloon skeleton structure. Bearing wall studs can be two by four inches in dimension thickness and the floor and roof beams two- by eight- or two- by10-inch dimensions.


Post and girt or braced frame construction, another skeleton frame used to build wood buildings, do not spread fire in the outer walls because the girder timber at each floor acts as a fire-stop. However, fire spreads to the attic space in a concealed space with voids enclosing plumbing pipes and electric wiring. There is a collapse danger in this skeleton frame that other wood frames do not have. The connection used in the corner post and (girt) girders is a mortise and tenon joint. These connections weaken the timber. The mortise hole weakens the corner post timber and the tenon tip cutaway weakens the girder end. This skeleton structure can suffer a sudden global collapse during a serious fire on the first floor. The walls fall out and floors pancake down when the four corner posts break apart at the mortise and tenon connection.

Platform construction is a modern skeleton construction that does not have wall concealed spaces extending from cellar to attic nor mortise and tenon joint connections. This is a superior skeleton framework of wood building. The fire spread problem is not in the outer walls, but in the concealed spaces in bathrooms and kitchens.

However, a deadly construction element has been introduced to platform skeleton structure called lightweight truss floor and roof beams and the glued wood I-beam. From a fire protection point of view, platform skeleton construction just went from being the superior framework to the worst. This inferior structure floor and roof beam element added to the frame of platform construction has transformed it to the most dangerous wood-frame skeleton structure from a collapse danger point of view. The platform frame skeleton is now lightweight truss construction and has become the most deadly wood structure. Firefighters must be warned to check the floor and roof beams during construction to determine if it is superior, solid beam or inferior, truss or I-beam quick-collapse material.


The structure framing battle plan:

chapter image Fig. 19.6  Type V wood construction structure framing.
  1. A concrete floor that is cracked, buckled or sagging is a structure framing collapse warning sign and Firefighters should notify the Incident Commander (IC) and not enter above or below the area of distorted flooring.
  2. When skeleton steel framing is not protected by missing or removed spray-on, fire-resistive material, it distorts and allows floor and roof framing collapse, especially if there are lightweight, thin, steel bar truss joists.
  3. Firefighters should know the framework of Type II construction performs poorly during fire. They should not operate on the roof of a noncombustible Type II skeleton steel construction framework using lightweight steel bar joist roof beams.
  4. Firefighters must identify load-bearing and non-load-bearing walls of Type III skeleton framework. The load-bearing wall framework supporting wood floors and roof are more likely to collapse when floors or roof fail because masonry wall framework has great compressive strength and can resist a load bearing down on it, but the same masonry wall has little tension strength created by sideway pressure buildup from broken floors piling up.
  5. Firefighters should know the column and girder connections of Type IV construction are unrestrained, resting on one another by gravity. Connections fail during fire; not the large timbers. Unrestrained connections cause skeleton framing columns, girders and floors to come crashing down similar to a house of cards.
  6. A Type V wood building is the only structure that has a frame of combustible bearing walls that can be destroyed by fire.

The game-changer

A game-changer of the framing of any building is if the building has been built before the local building code was enacted. This pre-building code structure may not have a standard frame structure. Another structure framing game-changer is if a building is located outside the town zoning limits. Both of these buildings will not have a standard frame required by code that an IC can evaluate during a fire. Both of these buildings have been grandfathered in by law. All bets are off in these buildings. The buildings can be built by amateurs without anything resembling a typical structure framework.

Structure Framing Battlespace Casualties

Boston, Massachusetts, June 17, 1972, Vendome Hotel infrastructure of columns, girders and bearing wall collapses, killing nine Firefighters. Google: “Full text of report of investigation of collapse at Hotel Vendome.”

Chapter 20: Stairway Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Stairs are the battlespace beachhead. Firefighters first must control the stairway to fight a structure fire. All fire operations start from a stairway. For example, stairways are where Firefighters start the search to locate fire; forcible entry operations take place; Firefighters begin the search for victims; the start of a hose-line interior attack; hose-lines in high-rise fires are connected to standpipe outlets; the escape route for people trapped in fire; the road where backup resources come from; and an area of refuge for Firefighters trapped in fires.

Firefighters must know how to use a stairway at fires. Some stairs have skylights at the top that can be vented. Stairs must not be overcrowded by Firefighters. If a wind-driven fire prevents advance from a stair, Firefighters must close the door, notify the Incident Commander (IC), protect the stair with the hose-line and attack the fire through a window with a hose stream with the wind at their back.

People coming down a stair to escape a fire have priority over firefighting. When people are coming down a stair, do not open a door to a fire area if it allows smoke to block their escape. Some stairs may be pressurized. When a building has two stairs, one stair is used to attack fire and the other is used to evacuate people. When a stair is designated for evacuation, stair doors leading from this stair to a fire area should not be opened. Only two or three stair doors from a pressurized door can be opened or it loses pressure.


Some stairs do not go to the roof. Firefighters should not go above an uncontrolled fire in a stair except to save a life. If stairs are not used correctly during a firefight, occupants and Firefighters can die. The following examines some rules of the stairway battlespace.

Open stair

Private dwellings are dangerous occupancies and each year, most men, women and children in America die in these dwellings. One of the reasons a private dwelling is dangerous is because of the open stairway. The open stair in a private dwelling goes from cellar to the top floor, where bedrooms are located and any fire on any floor that occurs at night spreads up the open stair, trapping sleeping people.

chapter image Fig. 20.1  Stairs are where the battle begins.

Multiple dwellings and commercial buildings are safer than our homes because these structures cannot have an open stairs; all stairs must be enclosed with one- or two-hour fire-retarding walls. Firefighters quickly learn the degree of danger when searching in different kinds of buildings with different types of stairs. Searching above a fire is extremely dangerous and the degree of risk varies with the type of stairway. An open stair of a dwelling creates the greatest risk for Firefighters searching above. Searching above a fire in an enclosed stair is less dangerous, as long as the doors are closed. And searching above a smoke-proof stair in a fire-resistive building or in a building with two stairs is even less dangerous. However, there is always a chance of being trapped whenever Firefighters go above a fire to search for victims.

Enclosed stair

An enclosed stair in a multiple dwelling is surrounded by walls built to resist fire for one or two hours and each door is protected with a self-closing spring hinge and a fire rating of one hour. This stair in a multiple dwelling is much safer than an open stair in a private dwelling. As long as the doors to the stairs are kept closed, smoke will not enter the stair.


There is one problem with an enclosed stair: When Firefighters open a door to fight a fire, smoke and heat flow over their heads up a stairway. At most fires when Firefighters attack a fire with a hose-line, they must hold the door open until they advance to the fire and it is extinguished. This allows smoke, heat and flame to enter the stair and trap any occupant trying to come down the stairs.

The firefighting strategy that should be used if people are coming down a stair is don’t open the door to attack the fire until all people are below the fire. Hold the door closed and notify the IC that you cannot attack the fire because people are coming down the stair. If there is another stair in the building, use it to attack the fire. This may be difficult to do, but it is the correct action; life safety comes before fire containment.

Smoke-proof stair

chapter image Fig. 20.2  When searching a floor above a fire, an open stair is the most dangerous stair to ascend and a smoke-proof tower stair is the safest.

A smoke-proof stair sometimes is called a fire tower in an enclosed stair that has an open-air balcony or an interior vestibule, with a smoke vent shaft leading to the open air. This intermediate vestibule is between the occupancy and the stair enclosure. Its purpose is to prevent smoke, heat or flame from following a person fleeing a fire from going into the stairway. It is sucked up the vent in the intermediate vestibule. For example, when a person flees a fire in an office, he or she opens an exit door and enters the intermediate balcony and any smoke or heat following the person will dissipate at the open-air balcony or flow up the vent shaft and not enter the stair enclosure.

There are two doors in a smoke-proof tower; one leads to the intermediate vestibule and the other to the stair enclosure. When an IC must decide what stair to use for attack and evacuating people, the smoke-proof stair should be used for evacuation, not for attacking the fire with a hose-line. An enclosed stair should be used for this purpose.

Because a smoke-proof stair’s intermediate vestibule is outside or contains a smoke vent shaft leading to the outside, having a door open and a path from the fire tower vestibule to a window opening in the occupancy can create a wind-driven fire flowing into the stair that can stop Firefighters from advancing an attack hose-line. For example, if there is a broken window in the fire area and a direct path from the window to an open door leading to the smoke-proof tower vestibule, you can create a super-heated fire flow path, exacerbated by a wind-driven fire shooting from the broken window to the smoke-proof tower vestibule open door. This will prevent advancement of the attack hose-line.


At several fires, when the door from the vestibule to the occupancy was opened to stretch the hose-line and attack the fire, heat and smoke swept into the vestibule, up the vent. So, remember, a smoke-proof stair should be the evacuation stair and another stair designated for attack with a hose-line.

There have been several major fires where a wind-driven fire was created when using smoke-proof stairs (fire tower) as an attack stair. When the door to the vestibule containing the air shaft was kept open for the hose-line and a window was opened by venting or fire, a wind-driven flow path was created, pulling fire and heat into the smoke-proof tower air shaft. So use a smoke-proof tower for evacuation, not as a fire attack stair.

Convenience stair

A convenience stair, also called an access stair, is an open stairway sometimes found in a commercial office building. This stair extends one or two floors for the purpose of allowing people to go from one floor to another without going out to a public hall to use the elevator. The general public does not have access to this open stair and it allows fire and smoke to spread from floor to floor if not enclosed.

When arriving at a fire, the IC should ask a building manager if there are any convenience stairs in the building and what floors they connect. Convenience/access stairs should not be used to launch a hose-line attack on a fire. However, if the initial and backup hose-line cannot advance on a fire because of wind or size of blaze, the IC may consider the possibility of sending an alternate hose-line up this stair as a last resort. Or, have a search and rescue mission go up this stair if people are reported trapped and the hose-lines cannot advance.

When a convenience stair is being planned during construction, the Fire Chief should insist an automatic fire door be installed to shut the opening when there is a fire and connected floors are protected with automatic sprinklers. Firefighters searching a floor above a fire in a fire-resistive building where normally there is no smoke spread, but there is an excessive amount of smoke detected, should notify the IC and warn of the possible presence of a convenience stair opening.

Scissor stair

Modern building codes allow scissor stairs. Scissor stairs are two stairs intertwined and built in one fire-retarding enclosure. These stairs get credit for two exits combined in one enclosure. Scissor stairs are possible because of a code defining the meaning of “remote exits” as a distance of 15 or 20 feet apart. This allows two exit doors to be close enough so two stairs can be enclosed in one shaft containing a scissor stair. Older building codes specified remote exits to be at each end of a floor area. The scissor stair saves money, but risks lives and makes firefighting more difficult.

Some scissor stairs open on alternate floors. One stair inside the enclosure opens on odd floors and the other stair opens on even-numbered floors. Some scissor stairs do not have partitions between the two stairs inside one enclosure. Smoke entering the enclosure contaminates two stairs.


The World Trade Center had so-called remote stairs that were both in the center of the 40,000-square-foot floor and when the terrorist plane sliced through the building, it severed all the center stairs. Buildings with scissor stairs should be inspected to determine how the design will complicate firefighting and ensure they are marked with stair designations and floor numbers.

Dead-end stair

chapter image Fig. 20.3  When there are two stairs in a building, during a fire, one should be designated for hoseline attack and the other for occupant evacuation. Doors from the fire area leading to the evacuation stair should not be opened.

All stairs do not lead to the roof; some stairs in commercial buildings terminate at an intermediate floor. Because we fight fires in residence buildings, we assume all stairs open out to a roof with a scuttle or bulkhead door. All stairs in residence buildings go to a roof, but some stairs in commercial buildings go to the roof and some do not. They may terminate at an intermediate floor or lead to a mechanical machinery room.

People sometimes are found dead at the top-floor landing of a dead-end or locked stair filled with toxic smoke from a fire below. When Firefighters open a stair door to a fire area, smoke and heat flow up the stairs, sometimes filling up a stairway. After a fire in a high-rise building is extinguished, the stair designated as the attack stair should be searched all the way up to the roof or termination level for trapped victims as soon as possible. Other stairs should be searched, too.

Dividing stair

After locating a fire in a high-rise building before the fire attack begins, stairs must be divided up for use; one stair used to attack the fire and one stair used for evacuating people from the building. After locating the fire, checking the stairs for construction and standpipe system, the Fire Officer on the fire floor should radio back to the Chief, identifying letters of the stairs to be used for firefighting attack and evacuation. The attack stairs should not be used for removing people because it will become full of smoke when Firefighters open the door to attack a fire. Generally, the stair with the standpipe outlet will be used to attack the fire.


If a stair in a high-rise building is a smoke-proof tower stair, use this stair for removing people because the smoke vent shaft can set up a wind-driven fire, pulling fire into the smoke vestibule. There must be a public address system and the IC can use it to direct people in the building. Announcements should be ordered by the Chief in Charge, to notify occupants of the identifying letter of the stair they should use to escape the fire. Especially after 9/11, critics argue the occupants will not listen to direction when the order is given to people in the building to stay in place. This may or may not be true. However, the IC has a responsibility to direct occupants during an emergency. The lawyers will want to know what instructions were given if there are any fatalities. We still must supervise evacuation.

Attack stair

When there are two enclosed stairs in a building, the Officer in command may designate either stairway as an attack stair to send Firefighters in with a hose-line or an evacuation stair to assist people leaving the building. The stair used as an attack stair is not used to remove people because the stair enclosure above will fill up with smoke and heat when Firefighters open the door to attack the fire.

When setting up in the stair designated for attack, the Officer in command should ensure as much as possible that no occupants are coming down the stair before the door is opened to advance the hose-line. If people are descending the stair, do not open the door to the fire area or you will trap people in the stair above the fire. Generally, the stair with the standpipe outlet will be the stair used to attack the fire and if there is a smoke-proof stairway, this stair should be used for removing people from floors above the fire.

Evacuation stair

chapter image Fig. 20.4  It is very important that stair doors are labeled to identify the stair enclosure and the floor or it is not possible to coordinate a fire attack and evacuation in a high-rise building.

As soon as possible when arriving at a serious fire in a building with two or more stairs, they must be divided up for use. Determine your strategy. Which stair will be used for stretching the hose-line to attack the fire and which stair will be used for occupant evacuation? The attack stairs should not be used for evacuation because it will fill up with smoke. The stair dedicated to occupant evacuation should be smoke-free, so doors from this stair to the fire area should not be opened during the fire attack.


During a fire in a high-rise commercial building, which has an open floor area where flames may spread quickly, people must be ordered to leave the vicinity of the blaze. Usually this includes the fire floor and the floor above the fire. Occupants on all other floors are directed to remain in place and not exit the floor until notified by the Fire Chief or if smoke enters their floor. At a high-rise commercial building, this strategy is to prevent overcrowding the exits. It is different at a high-rise residence building fire because apartments are subdivided by fire-resistive walls and all people (except the fire apartment occupants) are directed to stay in their apartments and not attempt to leave by the stairways. Tagging stair: Stair doors must be labeled to identify the stair enclosure and the floor. Firefighting in buildings with more than one stair is impossible unless all stairs are marked. In buildings with two or three stairways, each enclosure must have identifying letters on the outside of the door, such as “stair A” or “stair B.” Also, on the inside of the door, a floor number must be marked next to this identifying stair letter.

For example, the ground floor stair door would be labeled “stair A, floor #l.” This seemingly simple stair identification system is critically important for firefighting and occupant evacuation. If letters do not identify stair enclosures and the floor numbers, there can be no effective firefighting, occupant evacuation or controlled search and rescue.

Size-up stair

When Firefighters arrive on a fire floor and start to force open a door to a high-rise apartment and there is a serious fire inside, it suddenly can blow out into the hallway and engulf Firefighters and reduce visibility to zero. So before a door is forced, among those items Firefighters should size up are the stairs and hallway.

The size-up should include the exact location of the exit door leading from the hallway to the stairs. Next, check for any dead-end portions of the hallway. A dead-end portion of a hallway is an area beyond the exit door or a dead-end area off the main hallway. Also, if there is an open apartment door in the hallway, that may be used as an area of refuge if conditions change and smoke fills up the hall. If a fire flashes over and comes out in the hall, Firefighters must know exactly how to withdraw to safety. During forcible entry operations, use a rope around the doorknob or have a hook ready to pull the door closed after it is forced. A hose-line should be ready before starting forcible entry.

Stair doors

chapter image Fig. 20.5  When arriving at a fire and the hose-ling is not ready after forcing entry, temporarily close the door to keep fresh air from feeding the fire.

The most important part of any stairway is the door leading from the occupancy to the stair enclosure. To keep fire from spreading from room to room or stair to room, close the door. There was a fire in a New York City luxury apartment that killed a mother and two teenage daughters. The mother’s body was found at the window where she was calling for help; one daughter’s body was on the bed; the other on the floor. It was a 5th Avenue, duplex apartment connecting two floors, where fire spread up an open stairway into the bedroom where the family was trapped. The post-fire investigation revealed this pre-war apartment had a heavy wood and metal door that could have stopped fire and smoke from entering the room for several hours, but it was Fig. 20.5 When arriving at a fire and wide open. After the fire, the wealthy hus- the hose-line is not ready afband donated a lot of time and money for ter forcing entry, temporarily a smoke detector program. close the door to keep fresh air We all missed a lesson here--the door. from feeding the fire.

During a fire, close the door. Firefighters can use a door closing, too, when firefighting. For example, when arriving at a fire and the hose-line is not ready, close the door temporarily to keep the fire from spreading out into the hallway or up a stair. And after you force a door open, temporarily close it until the hose team is ready to advance. This will keep fire from spreading out of a fire room.

Upper stair

The most dangerous area of stair fire is the top floor. Fire, heat and smoke quickly spread upward to the top floor and mushrooms out, trapping people. When fire is spreading up a stair enclosure, the roof door skylight or scuttle should be opened to vent the stair fire at the top. If the top scuttle or skylight of the stair is vented and a stair door at the bottom is open, the stair becomes a chimney. Venting at the top of a stair may increase fire growth in a stair or quickly remove smoke from a stair. Either way, it will prevent fire and smoke from mushrooming out on the top floor.

The IC must have an objective before ordering a stairway vented at the top. Firefighters are taught in rookie school not to go above a fire in a stairway because they may be cut off by fire and not get back down. Despite this warning, each year, Firefighters are trapped above fires in stairways and have to jump out windows or be rescued by ladders. If you must go up a stair above a fire to rescue someone, use a ladder or climb a fire escape. If you must suddenly take this lifesaving effort to rescue someone, first close the door to the fire room and have another Firefighter stand by the door to prevent anyone from opening it until you return back down.

Collapse stair

Flame and smoke rise up a stair to a top floor, mushroom out and trap people in their rooms or apartments. Arson stairway fires can be different; they can burn downward. Either way, stairway fires are deadly.

Stair size-up

When you climb a stair in a burning building, you should size up its construction, because if things go wrong, you may be running, jumping or tumbling back down that stair. A stair is your access to a fire and your escape and you should know its construction. When climbing, look up at the underside of the stair above and then look down at the steps. Check out the soffit above the treads, risers below, then railings and stringers. A stair is your lifeline in a burning building and the truth is, some of us don’t know enough about stair construction. We study combustion and building construction, but we also should know about stair construction.

The following are some tips on how to size up a stair. There are three kinds of stair design--an open stair, enclosed stair and a smoke-proof tower stair. Each one presents different risks and protection during a fire.


Open stair

The first thing you must think about when climbing a stair going up to a fire: Is this an open or enclosed stair? The answer is going to determine your risk of getting trapped. The most dangerous stair is an open stair; an enclosed stair and smokeproof tower present less risk than an open stair. Unfortunately, an open stairway is found in private dwellings where we do most firefighting. It is a dangerous stair. Flame, heat and smoke can freely flow up an open stair behind Firefighters climbing to search second-floor bedrooms. Any fire from cellar to first floor, in any room, will flow up the open stair. Convection currents of heat rise to the top of an open stair, especially if windows have been vented. Climbing an open stair can be similar to climbing inside a chimney flue. Stair construction in private dwellings can be a modern, ladder-type stair without risers or a soffit; only treads and railing entirely built of wood, with a coating of flammable varnish or paint surfaces.

Veteran Firefighters use alternate tactics to rescue people trapped on the top floor of private dwellings that have an open stair; they use ladders or connecting fire escape balconies to get to windows of upper-floor bedrooms to avoid the open stair for rescue. Even if Firefighters are using the interior stair, fire department ladders are placed at windows for emergency escape in case fire cuts off escape.

Enclosed stair

An enclosed stairway is required by code in commercial, public and multiple dwellings. These stairs offer more protection than open stairs only as long as doors to apartments are closed. If a door to a fire apartment is open, flame and smoke quickly can spread into an enclosed stair and trap Firefighters above.

A size-up of the fire must take place in an enclosed stair at the fire floor before Firefighters climb a stair to go above. Firefighters should not search above a fire in an enclosed stair unless the size-up shows a fire company is extinguishing the fire in the apartment. This does not mean operating a hose-line in the hallway; it means advancing into the apartment and knocking down fire without any problems. If Firefighters are holding a defensive position at the door and not advancing on the fire or there is no hose-line at the fire, the door to the fire apartment must be closed before Firefighters search above. A Firefighter must be assigned nearby to ensure the door remains closed until the search above is ended and Firefighters have returned.

Smoke-proof stair

A smoke-proof stair, sometimes called a fire tower, is the best stair to climb up to a fire. This stair has an enclosed stair with a self-closing door opening up to an intermediate vestibule between the stair enclosure and occupancy. This vestibule is designed to prevent smoke and heat from entering the stair enclosure. This stair is found in commercial buildings and few Firefighters have never seen or used this type of stair.

A self-closing door leads from the stair enclosure to the vestibule and another self-closing door leads from the vestibule to the occupancy. The intermediate vestibule will have a standpipe outlet and a vent. This standpipe and smoke vent allow Firefighters to connect a hose, open the door to the occupancy and advance on the fire without causing smoke to enter the stair enclosure. Firefighters can go above the fire in the stair enclosure when the door from vestibule to stair enclosure is closed. Again, a Firefighter should be assigned at the fire floor to ensure this door remains closed until Firefighters return.

Stair construction

In addition to recognizing stair design when climbing stairs, Firefighters must be able to size up the stair construction. There are three basic types of stair construction–an L-shaped stair, a straight-run stair and a “U”-return stair.

An L-shaped stair

An L-shaped stair is a two-section stair that changes direction at a 90-degree angle and has one section longer than the other. An L-shaped stair most often is constructed of wood as an open stair in a private dwelling.


Straight-run stair

chapter image Fig. 20.6  An L-shaped stair most often is an open stair.

The most common stair construction is a straight-run stair. Straight-run stair construction is found in all types of building construction: Type I, fire-resistive; Type II, noncombustible; Type III, ordinary; Type IV, heavy timber; or Type V, wood frame. A straight-run stair has steps that rise in a 45- or 60-degree angle at an uninterrupted passage between two floors. Most often, straight-run stairs are stacked directly over one another. A person walks up one flight of steps to the floor above, then reverses direction, walks along a hallway to the foot of the stairs leading above, reverses direction again and starts up the next flight of stairs. A straight-run stair may have a fire-retarded soffit underside, a metal stringer on the outside carriage beam and metal handrail, but the interior framework of the straightrun stair interior usually is wood.

chapter image Fig. 20.7  Flammable liquids spilled down a stair can seep inside and attack the wood carriage beam supports, causing an entire stairway section to collapse.

Inside, a straight-run stair will be wood carriage beams, supporting the treads, risers and stair railing. Even though the exterior of a stair is noncombustible, the hollow interior supports are wood and fire sometimes can spread inside this hollow stair enclosure. Flammable liquids spilled down a stair can seep inside and attack the wood timber carriage beam supports.


There is another type of straightrun stair called a continuous straight-run stair. This continuous stair was built in century-old commercial buildings and flights of staight-run stair sections are not stacked over each other. Instead, the stair is one continuous, 30- to 45-degree angle, run from the front entrance up to the roof. At each floor level, there is an intermediate landing with an entry door to a commercial occupancy located off to the side. This “continuous” straight-run stair” is found in old, inner city, commercial, Type IV heavy timber manufacturing buildings. When climbing this continuous stair, a size-up should consider this an enclosed stair. Don’t go above the fire floor to search unless the door to the fire area is closed and you have a Firefighter lookout to ensure the door remains closed.

A U-return stair

The second most common stair is a U-return stair. Used in most modern commerial, public and mutiple dwellings, a U-return stair construction breaks up the climb at the middle of the stair rise and reverses direction with an intermediate landing. At the intermediate landing, a climber reverses direction and starts up the second half of the stair rise.

chapter image Fig. 20.8  If the treads and landing of a U-return stairway are marble and exposed on the underside, heat from a fire can weaken them and cause them to collapse on a Firefighter ascending or descending with tools.

A size-up while climbing this stair will reveal there is no soffit, so the underside of the stair construction can be examined more accurately than a straight-run stair. A U-return stair most often is constructed with a steel frame, steel risers with stone or marble, treads and intermediate landing platform. The handrails and carriage/stringer beams at both sides are steel. When climbing up to a fire, a Firefighter can clearly see the exposed underside of the steel frame and stone treads and intermediate landing above.

If the size-up reveals the underside of stone treads and the platform landing are visible, this should be a warning. These exposed stone parts of stair can collapse on a Firefighter descending with tools or when heated by fire coming out of an apartment or room impinging on the underside of the stone tread or platform. The steel U-return stairs that sustain most step and landing collapses are those with exposed stone underside and supported only by a one- or two-inch, angle-iron edge.

The most stable U-return stair is one where the underside of stone treads and landings are fully covered and supported with a steel support pan. Tread and platform collapse will not occur if fully supported by steel underside. A U-return stair is preferred in modern building construction because it reduces the amount of floor area for stair enclosure, adding valuable commercial or residence floor space.

After a Firefighter determines the type of stair and the construction, the size-up should continue by checking out the carriage beams, soffit, treads, risers and handrails.


Carriage beams

Carriage beams will not be visible in a L-shape or straight-run stair, because they usually are covered by a wire lath plaster soffit. But if you are climbing a stair in a Type III, ordinary, Type IV, heavy timber, or Type V, wood-frame building, you can be sure there are wood carriage beams behind the soffit. Two or three wood timbers with cutouts spaced for risers and treads will be supporting the straightrun stair section. The outer carriage beams sometimes are called stringer boards. These support beams are large wood timbers with 90-degree-angle cutouts that shape the stair. If these beams are destroyed by fire or dry rot over the years, the entire stair section can collapse. When one stair section collapses on the one below, the impact can cause the one below to collapse, triggering a progressive collapse of the entire stairway down to ground-floor level.

Investigations show us carriage beams do not break. Instead, the connections where they are attached to floors fail due to rotting or fire destruction and the weight of several Firefighters. Any type fire damage that burns through a floor near the top or bottom of a stair must be considered a warning sign of possible stair collapse. Fire damage to carriage beams can be caused by an arsonist spilling flammable liquid in a stairway and in vacant buildings subject to rotting over years of neglect.

An example of an arson-caused floor collapse occurred several years ago when a serial arsonist was starting stairway fires in New York City tenements. The arson method was spilling gasoline down stairs from the roof level, then escaping to adjoining buildings. At one fire, the carriage beams were destroyed and the entire stair flight from top floor to roof bulkhead collapsed down onto the stair below, narrowly missing Firefighters.

At an early-morning fire, on arrival of Firefighters, the top-floor walls and floor surfaces were aflame from a gasoline arson fire. Flames had not entered the apartments yet, just the top-floor hallway was ablaze. Firefighters with the hose-line were standing on the top-floor stair steps, waiting for water and when it got to the nozzle, they started extinguishing fire. Moving up the stair steps, they made the turn around the hallway railing, advancing to the rear, knocking down flame. They saw fire had burned a hole in the floor near the base of the stair section leading up to the roof level. They directed the nozzle stream into this hole in the floor at the base of the stair and suddenly there was a thunderous crash. When the smoke cleared, they saw the entire straight-run stair flight, leading from the top floor to the roof, had pancaked down onto the stair below, where they had just been standing. Investigation showed the flammable liquid had seeped into the stair from the steps and the carriage beams and the connection of the carriage beams to the top floor and roof level had burned away, causing the collapse.


A soffit is the protective underside of a flight of stairs that conceals the carriage beams. A soffit is noncombustible and fire-retarding. Years ago, soffits were not required or they could be made of wood wainscoting. Combustible soffit surfaces allowed fire to spread on the underside of stairs and added to fire spread in stairways.

In the past century, stairway fires trapped everyone in their apartments and required Firefighters to place many ladders front and back for rescue. The wood stair soffits, treads, risers, railings and carriage beams would burn and collapse quickly because they were not protected or enclosed. Today, surfaces and undersides of stairs must be noncombustible or covered with fire-retarding material. All doors leading to stairs must be self-closing. Transoms and wire glass doors are illegal.



When climbing stairs, Firefighters should look at the steps. A tread is the horizontal step area you place your boot upon when climbing. This should be stone or metal. If it is a stone or marble step, a Firefighter should know if it was heated by flame moments ago. It can crack and suddenly collapse when stepped upon, causing a leg to plunge through the metal frame and perhaps a kneecap injury. If the steel is still hot, it can cause a severe burn.

At one incident involving a large rubbish hallway fire under a first-floor stairway, there was a woman on the second-floor level calling for help. A Firefighter ran up the steps to assist, as others extinguished the blaze. A heated stone tread collapsed and the Firefighter’s leg plunged through a tread, causing injury and severe burns to his thigh. Knowing how to climb a fire-weakened stone stair and today’s bunker pants may reduce this danger.


The vertical part of a step is the riser and could help Firefighters avoid injury from a stone tread collapse. The steel riser can provide stability to stair climbing. When U-return stair treads and intermediate landings are cracked or missing, Firefighters should position their boot bottom on top of the riser and avoid placing weight on the tread or landing. The riser should support the foot instep. When stair treads have been destroyed by fire or are cracked and crumbling beneath the weight of a Firefighter, they can fail.

Veteran Firefighters climbing or descending a stair in a vacant building position their foot over the stair riser. A U-return stair often is built with stone treads and landings and steel frame. The stone treads and intermediate landings are a collapse danger, especially vulnerable to flame and heat damage. U-return stairs of steel and stone treads do not have soffits, so they can be sized up easily.


After Firefighters size up a stair design, its construction, carriage beams, soffit, treads and risers, they should check the stair railing. The term, balustrade, describes an entire stair handrail system: newel post, balusters (sometimes called spindles) and handrail. A newel post, the decorative post at the foot and top of the railing, secures the entire handrail to the stair and floors.

In vacant buildings, this decorative newel post and balusters--the vertical pieces supporting the stair railing--often are removed by salvagers and this weakens the entire stair railing. Firefighters bunching up on a stair landing suddenly engulfed in a heat blast from a flashover or backdraft tumble down a stair and if the railing collapses, will fall off the stairway.

A stairway battle plan:

  1. A stairway is the lifeline of a fire building. The first hose-line should be stretched to protect the stair and from there, advance and extinguish the fire. The stair must be protected during the duration of the firefighting operation so occupants and Firefighters can exit.  
  2. The second hose-line is stretched up the same stair to back up the first line. This is a fail-safe action to protect Firefighters and ensure stairway control. If a serious exposure hazard exists that requires the second hose-line, a third line is stretched up the stair as a backup line for the first one.

  3. Stairways should be vented at the top by opening skylights, scuttle covers and bulkhead doors when smoke prevents Firefighters from using them.
  4. Aerial ladders can be placed at roof level to give Firefighters access to a roof to vent stairs. Firefighters should not go up a stair above a fire to vent at roof level.

The game-changer

A blocked stairway is a game-changer. A stair can be blocked by people, fire collapse or during demolition or construction. When a stair is blocked, rescues and firefighting must be conducted from outside ladders and fire escapes. One of the lessons learned at the World Trade Center on 9/11 is the flow of occupants evacuating a building should not be interrupted or stopped. A minor time interruption of a line of people evacuating a burning building on a lower floor for several seconds can be magnified greatly on an upper floor close to the fire.

Stairway Battlespace Casualties

New York City Fire Captain and two Firefighters killed in stairway. Google: “Apartment fire: New York, NY, 62 Watts Street fire.”

Chapter 21: Fire-Resistive Building Construction Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A Type I fire-resistive structure is the best and the worst battlespace. When a fire is small, a Type I fire-resistive construction presents the least hostile battle environment. However, if the fire is not confined, this battlespace becomes the worst one of all. One reason this battlespace is good in the beginning of a fire is that it has the least amount of fuel in the structure to burn, compared to the other construction types. Concrete, steel and glass structures do not add fuel to a fire as does Type II construction with its combustible roof, Type III with its wood interior, Type IV with massive, exposed wood columns and girders or a Type V wood-frame battlespace that adds fuel from its interior framing and exterior walls.

Another reason a Type I fire-resistive building is a good battlespace at the beginning of a fire is that it has built-in fire protection to help firefighting. There may be a standpipe to make hose stretches shorter, a sprinkler system to prevent large fires and/ or smoke detectors to give us an early warning of fire. However, if the fire is not extinguished with the first and second hose-line, a Type I fire-resistive building fire can become a conflagration and present the greatest life and fire problem of a community. A high-rise building fire spreading flame from floor to floor can overwhelm firefighting resources of even the largest fire departments. The following are some of the firefighting problems of Type I fire-resistive construction that can turn a good battlespace into a conflagration battlespace and overwhelm the largest fire department.


Fire spread in a fire-resistive building

chapter image Fig. 21.1  Shows fire spreading on two floors in a fire-resistive building in NYC.
chapter image Fig. 21.2  Shows fire spread on five floors in a fire-resistive building in Los Angeles.
chapter image Fig. 21.3  Shows fire spread on nine floors in a fire-resistive building in Philadelphia.

The term, fire-resistive construction, is misleading. Fire and smoke can spread throughout a resistive building unless it is protected by automatic sprinklers or Firefighters’ hose streams. In 1950, the National Fire Protection Association (NFPA) defined a fire-resistive building to be a structure that would confine a fire to one floor, barring an explosion or collapse. This no longer is true. The National Institute of Standards and Technology (NIST) defines a fire-resistive building as a structure that will burn and not collapse. There is no mention of resisting fire spread in a future fire-resistive building definition. Examples of fire-resistive building construction and fire spread were demonstrated in three historic fires: New York in the 1970s, Los Angeles in the 1980s and Philadelphia in the 1990s.

These three high-rise fires in the 20th century documented the failure of passive fire protection--the ability of walls, floors and partitions to stop fire spread without assistance of automatic sprinklers or Firefighters’ hose streams.

In the 21st century, we have a new concern with Type I fire-resistive construction--global collapse. The total collapse of building #7 at the World Trade Center on 9/11 alarmed the building departments and fire service more than the collapse of the two towers. A terrorist plane did not strike building #7 and fire spread throughout the fire-resistive building because there was no working sprinkler protection and Firefighters were ordered not to fight the fire and instead to evacuate the surrounding area.

After burning for seven hours, this 47-story, fire-resistive building suddenly and completely collapsed down to a pile of rubble. NIST called it a global collapse--the entire structure, floor after floor, pancaked down into a pile of rubble.


Today, an Incident Commander (IC) should not depend on any type of construction to resist fire spread and now be concerned with structure collapse. The term, “passive fire resistance,” used by builders and engineers to describe how a structure alone could resist fire spread, is meaningless. The 21st century high-rise, buildings are lightweight structures that can spread fire from floor to floor and collapse. High-rise, fire-resistive buildings require “active fire resistance”–automatic sprinklers and Firefighters’ hose streams.

A recent 21st century fire spread problem in fire-resistive, high-rise and lowrise construction is combustible cladding fires.

Sometimes referred to as EIFS (exterior insulation finish system) fires, combustible exterior wall cladding or EIFS fires have become a major fire service concern and created another major avenue of fire spread in buildings that are supposed to resist fire. The outside walls of some Type I buildings now are highly combustible and spread fire quickly up the side of a building and then to the inside through windows. Spectacular EIFS fires can be started by a small outside fire or from the inside and spread out a window.

chapter image Fig. 21.4  A combustible exterior cladding fire fed by polyethylene in the façade. This is another high-rise outside fire spread problem, along with auto-exposure and curtain wall concealed spaces.

The cause of the United Kingdom Grenfell Tower fire that killed 71 occupants was flammable plastic insulation (polyethylene) installed behind new aluminum cladding during renovation. Sometimes, the exterior cladding problem is the flammable exterior cladding and other times, it is the flammable insulation or glue installed with the exterior cladding. Either way, this is a serious fire spread problem an IC must plan to stop.

A high-rise defend in place strategy is not an option during a combustible cladding fire. Similar to the strategy for the worst type of construction--Type V wood--in addition to inside hose-line placement, Firefighters must have an outside stream available to stop fire spread on the exterior walls of a fire-resistive building.

Fire can spread through the HVAC system of a fire-resistive building.

chapter image Fig. 21.5  The HVAC system continued to run during the MGM casino fire, which killed 85 people in Las Vegas, Nevada, November 21, 1980.

A heating, venting and air-conditioning (HVAC) system is one of the reasons fire-resistive buildings spread fire and smoke and do not confine fire and smoke. Some HVAC systems interconnect five or 10 floors with ducts and shafts for the purpose of heating and cooling. These HVAC ducts, shafts and poke-through holes penetrate every fire-resistive floor, wall and ceiling. Smoke and fire can spread through these openings.

Deadly smoke spread through a Las Vegas, Nevada, hotel air-conditioning system, killing 85 people. The fire started in the gambling casino and the air system carried the smoke and gases into the adjoining hotel. The air system was not equipped with smoke detectors arranged to shut down the system during a fire. So the HVAC moved the smoke and heat.

In addition, there were fire dampers designed to shut and stop fire spread in ducts. However, they did not close properly. They were heat activated and some of the deadly smoke did not reach the heat activation temperature. Smoke and heat were pumped throughout the so-called fire-resistive hotel for more than one hour by the air-conditioning system.


On arrival at a fire in a fire-resistive building, an IC must ascertain if there is a central air system serving the building. In many building codes, the activation of a smoke detector is designed to automatically shut the system down. However, the detector could be missing, not installed or broken. To be safe, an IC should order building management to shut the air system off. After a fire is extinguished, all floors served by the central air system must be searched because there could be a victim overcome by smoke coming from an air duct. Smoke can flow through the ducts of an air system even if the system is shut down. Convection currents move smoke several floors through a central air system when there is a fire on any floor served by the air cooling and air heating system.

Fire can spread horizontally through the ceiling space in a fire-resistive building.

A plenum is an undivided, suspended ceiling space, used as an air holding space for a heating and venting system in a fire-resistive building. It is used to temporarily store, supply or exhaust air recirculating in an HVAC system. This ceiling space can contain miles of combustible computer and electric cable insulation made of plastic or rubber, which emits a large amount of smoke when burning. A fire extending from the content into the plenum ceiling space can ignite combustible insulation and spread flame and smoke throughout the large ceiling space and to the floor above.

Firefighters entering a floor containing a suspended ceiling should use a pike pole to lift up a panel of the ceiling near the entrance door to examine the space for spreading flame and smoke. Fire should not be allowed to spread behind advancing Firefighters. If fire is allowed to spread unnoticed inside the ceiling space for some time, a large section of ceiling and framework could collapse, blocking the escape and trapping Firefighters.


Fire can spread near the curtain wall of a fire-resistive building.

chapter image Fig. 21.6  If the concealed space between the floor slab edge and curtain wall is not fire-stopped with a noncombustible filler, smoke and flame can spread vertically at this location.

Skeleton steel fire-resistive buildings often have an exterior curtain wall enclosing the structure like an outer skin. This so-called curtain wall can be constructed of aluminum, stainless steel, glass, masonry or plastic. It extends over the entire face of the building and is attached by bolts to the outer edge of the floor slabs on each level of the structure. However, there usually is a small space between the outer edge of the floor slab and the inside of the curtain wall through which flames and smoke can spread to the floors above.

Firefighters searching the floor above for fire spread in a fire-resistive building must check this space near the outer windows. If this concealed space is not fire-stopped with a noncombustible filler, smoke and flame can spread vertically at this location. Open up the outer wall partitions below the window on the floor above a fire and check the void for fire. Older high-rises have a panel wall, not a curtain wall. This panel wall rests on the outer edge of the floor slab. This exterior wall supported by the floor extends only one story and has no concealed space at the edge as does a curtain wall.

Fire can spread through floor construction of a fire-resistive building.

Floor construction in a skeleton steel fire-resistive building can consist of two or three inches of poured concrete on top of fluted metal deck. Flame can spread through this floor. Heat can cause a concrete and fluted metal floor above to sag, warp and crack at a seam and spread fire upward. At a serious fire in a fire-resistive building that burns uncontrolled for an hour or more, the suspended ceiling is destroyed and flames can heat the underside of the fluted metal deck. At this time, the fluted metal deck above the hottest part of the fire below sags downward and the concrete above it cracks open. Flame can spread through the cracked concrete to rugs and furnishings.

chapter image Fig. 21.7  Cracks in the floor and sagging concrete allowed fire to spread to the floor above at the Bankers Trust building fire on 48th Street and Park Avenue, New York City, January 31, 1993.

Here's how an eyewitness observed fire spread in a fire-resistive floor at a high-rise fire. “First, the floor above the fire filled with smoke, heat and combustible gases. Next, a so-called ‘pilot’ flame rose up through the cracked concrete floor, three or four feet into the super-heated gases on the floor above and ignited the area. Floor after floor in the fire-resistive building filled up with super-heated combustible gases, then the ‘pilot’ flame came up through the cracked and sagging floor to cause sudden ignition.”

After a fire in a fire-resistive building is extinguished, sagging floors and warped steel girders and beams may have to be shored up before Firefighters can safely perform salvage and overhaul. Flame also can spread from floor to floor in utility closet poke-through holes in the floor containing electric wires, water piping and computer cables; and outside, a fire-resistive building by auto-exposure, flame spread from window to window above.

Spray-on, fire-resistive material (SFRM) does not insulate a steel structure.

chapter image Fig. 21.8  The Bankers Trust fire spreading to floor above. Interior forces were unable to advance on this fire. Two aerial platforms extinguished the fire or it would have continued to spread.

The steel in a skeleton steel fire-resistive building can fail at temperatures of 1,000 to 1,100 degrees Fahrenheit (538-593 degrees Centigrade), depending on its load. Building codes require structural steel to be protected from the heat of a fire and one commonly used fire protection method is a spray-on, fire-retardant surface coating of vermiculite or perlite. The underside of a concrete floor in a fire-resistive building is fluted metal floor construction supported by steel girders and beams. The entire steel surface must be covered with fire-retarding spray coating thick enough to provide a fire-resistive rating of at least two hours. However, tests and fire experience show the SFRM is ineffective.

chapter image Fig. 21.9  At the Bankers Trust building fire, there was no spray-on, fire-retarding material on the steel structure and the fire floor had to be shored up before overhauling began.

In my experience, after every serious fire, the steel spray-on fire coating is missing and the steel is warped, buckled or sagging, with bolts missing. And, according to NFPA, Vol. II, sec. 19-52, the “spray-on coatings are suspect in their effectiveness.” They are ineffective because when applied in a spray, it does not cover the steel completely, the thickness of the coating is insufficient and there is not proper adhesion in the sprayed material to keep it on the steel; the air systems blow it off the steel.

Other reasons spray-on, fire-retarding material fails to protect steel of a fire-resistive building include:

  • Failure to prepare the steel for spray-on coating adhesion. The steel must be free of rust and dirt and not coated with primer paint. If not, the spray-on, fire-retarding coating will scale and fall away from steel.
  • Poor or uneven application of the spray-on, fire-retarding material.
  • Variation of spray-on material mixture during manufacture makes it ineffective.
  • Failure to replace spray-on material dislodged by other tradespeople performing work around the steel during construction of the building.
  • The investigation of the WTC fire and collapse by NIST determined there is no documentation or evidence to justify the claim of a thickness of ¾- or 1½-inch will provide two-hour, fire-retarding protection of steel.

Automatic sprinkler systems can fail.

Records show sprinkler systems successfully control fire in 93 percent of the incidents. However, sprinkler systems are designed to control a fire, not extinguish a fire. Firefighters are needed to extinguish the blaze after the sprinklers control it. They also are required to search for trapped or injured victims; they must shut the sprinkler system off after the fire is extinguished to prevent water damage; and, finally, they must replace sprinkler heads and put the system back into service.

The NFPA estimates that sprinkler systems fail at seven percent of structure fires (one of every 14 fires), primarily due to human error. “Two-thirds (65 percent) of the sprinkler failures to operate were because the system had been shut off before the fire. Another one-sixth (16 percent) occurred because manual intervention defeated the system; this can happen when building management or the Firefighters at the scene shut off the sprinklers prematurely. Lack of maintenance accounted for 11 percent of the sprinkler failures and five percent occurred because the wrong type of system was present.” Even though automatic sprinklers have a stored water supply or connection to a water main, an IC always must order a hose-line stretched to augment supply water to a sprinkler system.


Standpipe hose systems can fail.

chapter image Fig. 21.10  The first hose team must consist of an Officer and four Firefighters on the fire floor, one water supply Firefighter on the floor below and one in the street to supply the standpipe.

Most Type I fire-resistive buildings have standpipe systems. Firefighters depend on this piping system to get water to the upper floors and if the system fails, the firefighting fails. Instead of stretching 10 or 12 lengths of hose up a stair, only three or four folded hose lengths are carried up by Firefighters in an elevator and connected to the standpipe outlet on the floor below the fire. A Firefighter in the street connects a supply hose-line to a Siamese and pressurizes the system with water. A standpipe system, like a sprinkler system, can fail due to human error or poor design.

For example, the standpipe system in the Philadelphia Meridian Plaza fire-resistive building could not be used because pressure-regulating valves at the outlets limited water pressure to the hose streams and these outlet valves required special tools to adjust the pressure, tools the Firefighters did not have.

At another famous fire, the standpipe system in the Los Angeles First Interstate fire-resistive building was shut down and not supplied with water due to installation of a sprinkler system. This fire spread five floors because there was insufficient water pressure for the first 40 minutes of the fire. Another design defect at this high-rise fire was the installation of standpipe aluminum outlet valves inside the occupancies. The flames melted the aluminum valves, allowing water to drain from the standpipe system.

The most common problem using a standpipe system at a fire is low water pressure. An IC must consider several alternate strategies when notified of a standpipe system low pressure problem. The first strategy is to order pump operators to increase engine water pressure. A rule of thumb for standpipe engine pressure is 50 psi for a smooth bore nozzle, plus 20 psi friction loss for four lengths (200 feet) of 2½-inch-diameter hose stretched off the standpipe outlet (80 psi flowing pressure reading on in-line pressure gauge), plus five pounds pressure for each floor above ground level to compensate for “head pressure” necessary to overcome water weight in the pipe, plus an extra 25-pound pressure for friction loss in the standpipe and supply lines to the inlet.

Another alternate strategy for low pressure is to order Firefighters to remove any pressure-regulating valve from the outlet. This valve may be restricting water. Another alternate strategy an IC can take if the standpipe has a pump system in the basement is to send a Firefighter with an engineer to start pumps and increase water pressure delivered by building pumps. Last, but not least, check the hose for “kinks.”

Fire can spread in stairways of fire-resistive buildings.

There are three kinds of stairs in a Type I fire-resistive building:

  1. a smoke-proof stairway
  2. an enclosed stair
  3. an access or convenience stair. The enclosed stair and the access stair can spread fire and smoke on several floors. A smoke-proof stair is a superior stair that prevents fire and smoke spread. This stair is found in Type I fire-resistive commercial office buildings.

A smoke-proof stair is an enclosed stair that requires people fleeing a fire to first pass through an open-air balcony or intermediate vestibule containing a smoke vent. This open-air balcony or interior vestibule is designed to dissipate smoke, heat or flame. For example, during a fire when a person leaving an office floor opens a self-closing exit door and enters the open-air balcony or interior vestibule, any smoke or heat following will dissipate up the vent shaft. The occupant passing through this vestibule then must open another self-closing door to enter the smoke-free stair enclosure.

chapter image Fig. 21.11  The smoke-proof tower should be used for evacuation and an enclosed stair for hose-line attack.
chapter image Fig. 21.12  Stairs must be divided; one used for evacuation and the other used for fire attacks.

An enclosed stair is the most common stair in a Type I fire-resistive building. It has an enclosure and door that retard the entry of smoke and fire for up to 1½ hours, but it does not have an intermediate vestibule to dissipate smoke and flame. When you open the door from the stair enclosure, you enter the floor with the fire. This open door allows smoke and heat to spread into the stair enclosure. If Firefighters hold the door open for an advancing hose-line attack, heat, smoke and flame spread into the stair. Anyone in the stair above the fire trying to descend will be engulfed in smoke and heat.

In 2014, one person was trapped and killed in a 38th-floor hallway as Firefighters fought a fire on the 20th floor of a fire-resistive New York City high-rise apartment building. In Chicago, six occupants trying to escape a fire died in a smoke-filled enclosed stairway as Firefighters opened the door to attack the fire.

An open stair, called an access or convenience stair, is allowed in Type I fire-resistive buildings. These stairs are not considered an exit and they are constructed near an executive office to allow quick access from floor to floor without going out into a public hall using an elevator or public stair. These open stairs may connect two or three floors without any enclosure to prevent spread of smoke or fire from floor to floor. One of the first items an IC should look for when examining floor plans during a fire is the presence of open stairs. These open, access or convenience stairs can spread fire, heat and smoke rapidly from floor to floor. When a Firefighter discovers an open stair, the IC should be notified of the floor numbers served by the stair. This information will affect the firefighting strategy.

Elevators in fire-resistive buildings fail during fire.

Elevators fail during fires, trapping occupants and Firefighters three ways in fire-resistive buildings:

  1. The elevator car can take occupants up to a fire floor and doors open into a flaming hallway.
  2. The elevator car suddenly can take occupants above an uncontrolled fire and trap them in a smoke-filled shaft.  
  3. An elevator car can stall in a shaft between floors and trap occupants in the car until rescued.

With this deadly information, Firefighters must realize that the elevator can be a deadly trap during fire. Regardless of whether the elevator is equipped with an emergency mode “Firefighter service,” extreme caution must be used when operating an elevator during a fire. Fire, heat, smoke, power loss, overheating of the equipment and runoff water from hose streams or sprinklers can cause elevators to malfunction. An IC using an elevator during a fire must have a plan to monitor the elevator movement, an escape plan if the car stalls and a plan to stop an out-of-control elevator heading toward a fire floor.

chapter image Fig. 21.13  Take an elevator two or more floors below the reported fire floor.

There are three phases of elevator operation systems. Phase I elevator system is defined as the automatic or manual recall of elevators to the lobby of a high-rise building designed to recall elevators and prevent building occupants from using them during a fire. Phase II elevator system (Firefighter system) allows a Firefighter to operate an elevator from within the car in an emergency mode after the Phase I system has recalled Firefighters to the lobby. The Phase III elevator system, proposed by some fire departments, is the name given to a future elevator car that would be constructed in a fully enclosed fire- and smoke-protected shaft enclosure, with a wiring system insulated from the effects of water and fire that could be used safely during a fire.

During a major fire of long duration, a Firefighter should be dedicated to the task of continuously operating the elevator and in case of emergency, be equipped with a radio and forcible entry tools. If the elevator stalls or malfunctions in any way, the Firefighter immediately should notify the IC of the situation.

To determine the effectiveness of a Phase II system, the Firefighter running the elevator temporarily should stop the elevator at an intermediate floor to see if the elevator stops as required. If the elevator does not stop at the intermediate floor, this indicates the Phase II “Firefighter service” mode is not functioning properly. The Firefighters should exit the elevator. The elevator could be out of control and heading for the fire floor. An Officer entering an elevator car with a company should ensure the correct floor button is pushed or identified when going up to a fire. Do not delegate this important action to a Firefighter who may not understand the importance of this life and death assignment.


A fire-resistive building battle plan:

chapter image Fig. 21.14  The 110-story World Trade Center towers battlespace collapsed into a pile of rubble within seconds. When it was built, it was hailed as a “leap to lightness.” It is an example of lightweight high-rise construction. Designed by architect Minoru Yamasaki, its “hollow tube frame” bearing wall structure used 40 percent less structural steel than traditional high-rise building design and had lightweight bar joist truss floors.
  1. Type I passive fire protection from walls, floors, ceilings and roofs cannot be depended upon. The advantage of passive fire protection provided in modern construction is being lost by cutting costs and the use of lightweight materials.
  2. Auxiliary appliances, such as sprinklers, standpipes and smoke detectors, are like coalition forces in the Middle East war; you must use them, but they sometimes are unreliable.
  3. Even when auxiliary appliances, such as sprinklers, work effectively, Firefighters are needed on the fireground to quench spot fires, search for unconscious victims, perform salvage and overhaul and, most important, to ensure there is no rekindle.
  4. For combustible cladding fire outside, aerial master streams must be positioned and interior search for fire spread and possible total evacuation considered.

The game-changer

The game-changers occur when a hose-line cannot be advanced because a fire is too large, a wind-driven fire is preventing advance, a terror incident or exterior insulation finish system is spreading fire on the exterior of the building. When one of these incidents occurs, strategy must be changed from an offensive to a defensive attack.

When a large fire prevents extinguishment, a strategy called “controlled burning” may be an option. During controlled burning operations, Firefighters remain in the stair enclosures directing hose streams and rescuing people until all the fuel on the floor is consumed by fire. There is a limit to how long Firefighters safely can remain in a fire-resistive building during a controlled burn. The steel structure floors are protected from fire for only two or three hours. If the controlled burn continues for longer than this, an IC must consider withdrawal and strategy change.

Firefighters were withdrawn from a high-rise fire for the first time at an uncontrolled fire in Philadelphia, Pennsylvania, by Chief Roger Ulshafer in 1990. All interior firefighting was stopped and Firefighters withdrawn from the burning building because of the collapse dangers. Ten years later, as ordered by a judge, the 38-story building was torn down because it was too dangerous to rebuild.

Another game-changer is a combustible cladding fire.

Type I Fire-Resistive Building Battlespace Casualties

New York City Captain and two Firefighters died in a Type I, high-rise, fire-resistive building at a wind-driven fire. NIOSH Firefighter fatality investigation F 99-FO1

Chapter 22: Noncombustible / Limited Combustible Construction Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


The first three things Firefighters must know about the Type II, noncombustible/ limited combustible building battlespace:

  1. The steel structure is not protected against heat of fire; the steel columns can quickly buckle, sag or warp.
  2. The roof deck is combustible. If fire spreads to the asphalt roof decking, it can spread over the entire building.
  3. The unprotected lightweight steel truss joist can fail in five minutes when heated by fire.

The law allows there be no fire-resistive material protecting this type building and fire protection engineers warn us that the thin bar trusses can lose their load-bearing capability at fire temperatures of 1,000 degrees Fahrenheit (538 degrees Centigrade). The second part of the construction term, “limited combustible,” often is forgotten or left out of the term, noncombustible. The part of the building that causes “limited combustible” to be added to noncombustible is combustible asphalt/plastic/insulation paper roof deck.


When you read NFPA standard 220, which states the type of fire protection required for all five types of construction, you will see Type II is the only one with 000, meaning the fire protection for walls can be -0, framework can be -0 and floors can be -0. Firefighters must be aware of this Type II, noncombustible/limited combustible construction. It is the most popular construction today, replacing Type III, and is used in today’s malls, shopping centers and commercial office buildings. This is the battlespace of the future. The following is information Firefighters must know about this cheaply constructed, widely used construction battlespace.

The “new normal” construction

Type II, noncombustible/limited combustible construction buildings are replacing Type III, ordinary construction buildings in our downtown main streets, suburban shopping malls and suburban warehouse distribution centers. It is a common commercial building. A Type II constructed building can have an infrastructure of steel walls enclosing a steel truss framework; it can be a masonry bearing wall building supporting steel bar trusses; or it can be masonry non-bearing walls enclosing a framework of columns, girders and bar joist trusses supporting floors and roof. This type building is called noncombustible, which means the structure does not add fuel to a fire.

However, experience has shown there are combustible parts of a Type II structure. They are the roof covering and the insulation on wiring and cable inside the building’s storage closets and suspended ceiling spaces.

chapter image Fig. 22.1  Type II, noncombustible/limited combustible construction is designed and built for low-hazard content, not high-hazard content.

Years ago, a serious fire in a GM super-large, one-story automotive plant burned for days in a roof deck. It burned tons of asphalt, tar and combustible insulating paper on the roof, collapsing and destroying the entire structure. Since this fire, the term, limited combustible, was added to the construction name. However, it is the combustible material stored inside the building that presents the main hazard of Type II construction. When sizing up a building fire, you must consider both the fuel load in the structure and stored inside the structure.

In 1991, in Brackenridge, Pennsylvania, the content fuel load in a Type II, noncombustible building was high hazard–furniture refinishing with drums of flammable liquids. During the fire, the floor collapsed and caused the death of four Firefighters. Fire in a cellar heated unprotected steel columns and girders, causing a floor collapse, trapping four Firefighters on the first floor above.

Another tragic fire in a Type II, noncombustible/limited combustible building in Charleston, South Carolina, in 2007, contained high-hazard storage of sofas, chairs and mattresses. The rapidly spreading fire and smoke trapped nine Firefighters. (NIOSH Firefighter Fatality Investigation 2007-18.) Both of these fires occurred in Type II, noncombustible buildings containing high-hazard and high fuel load, which was unprotected by automatic sprinklers. The lesson learned from these two tragic fires is a Type II building is designed and built for low-hazard content, not high-hazard content.

If the occupancy changes to a higher hazard, it must have automatic sprinkler protection installed. A low-hazard occupancy, when consumed by fire, does not exceed, on average, 100,000 BTUs of potential heat release per square foot. Examples are offices, restaurants, hotels, hospitals, schools, museums and libraries. A moderate hazard occupancy generates between 100,000 and 200,000 BTUs of potential heat release per square foot. Examples are retail shops, factories and workshops. High-hazard occupancies generate between 200,000 and 400,000 BTUs per square foot. Examples are warehouses, woodworking shops and bulk storage buildings. The fuel load inside a Type II building is more significant than the fuel load built into the structure.

Noncombustible construction is not fire-resistive.

Firefighters must understand the difference between the terms, noncombustible and fire resistance. They are not the same thing. The term, noncombustible, means the structure does not add fuel to a fire. The term, fire-resistive, means the structure will resist fire for a specific length of time.

Steel is noncombustible, but has no fire resistance. Unless it is protected with fire-retarding insulation, steel fails quickly. A protective covering of concrete, terracotta, plasterboard or spray-on, fire-resistive coating can give noncombustible steel fire resistance. Depending on the thickness of the insulation covering steel columns and girders, a building can be given a fire-resistance rating of one two, three or four hours. A Type II structure of steel can be unprotected or have a fire-resistance rating.


To determine if a noncombustible building has any fire resistance, look at the Arabic numbers that come after the Roman number designation on the certificate of occupancy. For example, a building may be classified Type II, 211 noncombustible/limited combustible. The Arabic numbers following the Roman numbers mean the exterior walls have a two-hour, fire-resistive rating; the columns and girders have a one-hour, fire-resistive rating; and the floors have a one-hour, fire-resistive rating. The three Arabic numbers after any construction Type I, II, III, IV or V, indicate the fire-resistive rating. The first number describes the fire resistance of the exterior walls, the second the structure framework and the third Arabic number the floors.

Notice that in a building code, there is no rating for the roof on any of these five types of building construction classifications. Actually, you will find most Type II constructed buildings have no fire-retarding protection for the steel structure. The designation will read Type II 000. The zero designations after the Roman number II mean no fire resistance for exterior wall, structural framework or the floor construction.

Truss construction fails quickly.

chapter image Fig. 22.2  Unprotected roof bar joist trusses became heated, sagged down and pulled the truss ends off the bearing wall. Steel bar joist trusses can fail within five to 10 minutes of fire exposure.

A Type II noncombustible building is a truss building. The floors and roof are constructed using thin steel bar trusses. The steel bar truss is composed of a long steel bar (web), bent at 90-degree angles and welded to angle irons (chords) at the top and bottom. This bar joist can fail and collapse a roof or floor in a noncombustible building within five to 10 minutes of fire exposure.

The 20th edition (like the 10th to 19th editions) of the Fire Protection Handbook, National Fire Protection Association, volume II, pages 19-50, state that unprotected steel bar joist can fail after five to 10 minutes of fire exposure. This warning by the architects and engineers who write the handbook are telling us something important. It is the only structural element with such a short failure time, stated repeatedly in every edition of the handbook of fire protection for the past 50 years. A structure is only as strong as the weakest member. This is a warning of early collapse and a startling admission of how dangerous this steel bar truss beam is during fire. The World Trade Center towers had 60-foot-long steel bar trusses supporting floors.


Combustible roof

The combustible parts of a noncombustible, Type II building are found in the rooftop and combustible insulation covering wire and electric cables. The most combustible material is in the roof covering. Several layers of mopped asphalt, tar paper and layers of insulation paper can be found above a metal fluted roof. The post-fire investigation of the automotive plant fire mentioned on page 270 discovered there were 2,000 tons of tar (asphalt) in the roof covering that burned and destroyed the building.

chapter image Fig. 22.3  The rigid insulation may be polyurethane and the top dressing may be another layer of tar or asphalt.

After the fire, the NFPA published a standard, recommending roof construction in Type II buildings:

  1. The layers of paper and plastic over the metal roof must be noncombustible.
  2. The tar coating between layers must not cover the entire roof surface, but instead be applied in strips over only the intersections where the panels of metal, plastic and paper meet. This so-called “strip mopping” is designed to reduce the amount of combustible tar and asphalt and it is recommended not to apply more than 15 pounds of tar per 100 square feet.

What does all this mean to a Firefighter? It means if you have a fire in a Type II building and the underside of the fluted or corrugated metal roof has a black burn mark, send a Firefighter to the roof and check the roof cover for possible fire extension. Heat could have been conducted through the metal roof to the combustible roof covering above. Also, the NFPA standard is not a law; it is a recommendation unless the local building code commissioner adopts it as law.


Unprotected steel

Unprotected steel columns, girders and bar joists fail when heated by fire. Structural steel does not melt during a fire, but steel will fail. The steel loses load-bearing ability and will warp, sag, twist, bend and expand. To prevent steel from moving and make it fire-resistive, steel must be covered with fire-retarding material. It is stated that at temperatures of 1,000 to 1,100 degrees Fahrenheit (538 and 593 degrees Centigrade, respectively), steel loses 40 percent of its load-bearing capability and no longer will support its designed load. At a fire, 1,000 degrees Fahrenheit is reached easily.

The standard time/temperature curve test fire, which is considered an average fire temperature and is used to determine fire-resistive standards, shows a typical fire reaches 1,000 degrees Fahrenheit in five minutes; 1,300 degrees Fahrenheit in 10 minutes; 1,700 degrees Fahrenheit after one hour; 2,000 degrees Fahrenheit after four hours; and 2,400 degrees Fahrenheit--the highest temperature of the test fire--is reached after eight hours. A typical structure fire’s maximum temperature reaches 1,700 degrees Fahrenheit. It takes 2,400 degrees Fahrenheit to melt steel. This temperature is not common at a typical structure fire.

Venting smoke and heat

Firefighters should not be sent to the roof of a Type II, noncombustible building for roof venting. If a fire in a Type II building is large enough to require roof venting, it is too dangerous to operate on the steel bar truss roof to vent. After flashover, the temperature of the fire can be 1,000 degrees Fahrenheit and this temperature can cause the bar trusses to fail within five or 10 minutes of exposure. Firefighters must understand that as these Type II constructed buildings replace Type III, brick and wood-joist construction, most of our firefighting experience and size-up skills are not transferable. Our training for roof venting operations has been developed on a wood-joist roof and is not safe for working on Type II buildings, especially since the NFPA has been warning us for 40 years that this roof can fail within five or 10 minutes.

An alternative venting is window venting. Instead of ordering Firefighters to the roof, Incident Commanders (ICs) should change the strategy to horizontal ventilation. If that cannot be accomplished, an exterior attack, using master streams, must be the strategy.

chapter image Fig. 22.4  If a fire is large enough to require roof venting, it is too dangerous to operate on the steel bar truss roof to vent.

Some one-story, noncombustible buildings using lightweight steel bar joists are constructed with large rectangular windows at the upper portion of the masonry enclosure walls. These windows are very effective for horizontal smoke venting during a fire. Located at the top portion of the walls, where heated smoke would accumulate, these windows have a horizontal length greater than the vertical height of the window. Ventilating several of these windows can be accomplished faster and more safely than making a roof cut. Roof ventilation has been very effective and relatively safe when carried out on a Type III, ordinary constructed building wood-joist roof, but this no longer is true with steel bar truss joists, lightweight wood trusses, wood I-beams and metal C-beams.

Steel failure

Four factors determine the speed with which steel will fail during a fire:

  1. Temperature of the fire
  2. The load stress
  3. The steel thickness
  4. The fire size

A heavy, thick section of steel has greater resistance to fire than a lightweight section. A large, solid steel I-beam can absorb heat and take a relatively long time to reach its failure temperature (1,000 to 1,100 degrees Fahrenheit), while a lightweight steel beam, such as an open-web bar joist, can be heated to its failure temperature quickly.

The failure temperature is the temperature inside the steel member, not the surrounding atmosphere. By increasing the mass of a steel structural element, we can actually increase its fire resistance to a limited degree. An unprotected, built-up steel column of sufficient mass could be given a one-hour, fire-resistance rating if tested in a furnace. This could happen if the unprotected steel absorbs heat and does not reach the failure temperature of 1,000 to 1,100 degrees Fahrenheit for more than one hour. In this instance, the heat sink property of a large, thick piece of steel lengthens the time required for the temperature of the steel to reach the collapse temperature. However, even large-sized steel eventually will collapse in a fire.

In the graphic below, the left column is arranged according to structure fuel load. The right column is arranged by collapse potential and based on an informal survey of fire departments taken during lectures around the country. Your department should rearrange this left column to reflect your experience and community.

Relative Structure Fuel Load      Relative Collapse Potential
Small Type I, Fire-Resistive Type I, Fire-Resistive
Type II, Noncombustible* Type IV, Heavy Timber
Type II, Ordinary Type V, Wood Frame
Type IV, Heavy Timber Type II, Ordinary
Great Type V, Wood Frame Type II, Noncombustible*
chapter image

* Type II has a small amount of structure fuel, but has great collapse danger due to steel bar trusses.


Combustible content

A Type II, noncombustible building is designed to house low-hazard content. When you analyze a building for fire hazard, you must evaluate the structure’s fuel load and the content fuel load. The fuel load built into a structure is constant and does not change unless there is a major renovation. However, the fuel load created by the content placed inside the building varies greatly and changes with new occupants. Different owners will bring fuel into a building and this may increase or decrease the amount of the content fuel load.

When evaluating the fire hazard of a structure, the amount of content fuel load inside a building is much more important than the structure fuel load. If the fuel load introduced into a Type II building with a new occupant increases the content fuel load, there must be additional fire protection, such as automatic sprinklers. A change of occupancy from low-hazard to a high-hazard occupancy without additional sprinkler protection was one of the factors contributing to the deaths of the Firefighters in Brackenridge, Pennsylvania, and Charleston, South Carolina.

Fire protection

chapter image Fig. 22.5  Air movement from an HVAC system blows the spray-on, fire-retarding material off the steel.

There are three methods to protect steel bar trusses in Type II, noncombustible construction:

  1. encasement
  2. fire-retarding ceiling (membrane ceiling)
  3. spray-on, fire-retarding material (SFRM).

The encasement method of coating the steel with concrete is expensive and rarely done and fire-retarding with a membrane ceiling is effective only when the ceiling panels are tight and in proper position. Examine the next panel ceiling you see in a store and you will realize this is rarely true. Panels will be missing or improperly set in the ceiling framework and there will be poke-through holes in the ceiling for light panels, air transfer ducts, pipes and wiring.

The third method of protecting steel bar truss construction--spray-on, fire-retarding--uses a slurry of vermiculate, volcanic rock and/or mineral fiber. Problems with the spray-on, fire-retarding include:

  1. The steel is not properly cleaned and free of primer paint.
  2. The slurry is not mixed properly.  
  3. The spray does not cover all the steel surfaces.
  4. Other workers scrape off spray material to perform later work.
  5. Air movement from an HVAC system blows the spray off the steel.

So the statement from the NFPA that says when “unprotected,” the steel bar truss fails within five or 10 minutes. Even when “protected” with one of the above three methods, the steel bar truss can fail quickly during fire.


chapter image Fig. 22.6  The key to safe operations at a fire in a Type II noncombustible building is early identification of the steel bar truss.

The key to safe operations at a fire in a Type II noncombustible building is early identification of the steel bar truss and early transmission of this information to the IC. The information must be reported to Command before safety actions can be directed. Never assume the IC knows the collapse danger due to the presence of a truss. Firefighters are the eyes and ears of the IC.

A noncombustible/limited combustible building battle plan:

  1. Incident Commanders and Firefighters have limited firefighting experience and have not yet fully evaluated its fire and collapse dangers, so caution should be used.  
  2. To date, Type II, noncombustible/limited combustible battlespaces have resulted in the deaths of 13 Firefighters: Brackenridge, Pennsylvania, four Firefighters; and Charleston, South Carolina, nine Firefighters. The 1950s General Motors Livonia, Michigan, fire revealed the combustibility of the roof deck and the 2001 collapse of the floors of the World Trade Center towers revealed the collapse danger of steel bar joist floors on 9/11.
  3. Type II battle plan must include caution when roof venting on the structure. The fire service has been warned constantly by the NFPA of the early, five- to 10-minute collapse danger of unprotected steel bar truss joists. Horizontal cross venting should be the plan of action, with the use of positive pressure fan venting.
  4. Noncombustible/limited combustible structures should house only low-hazard content because of its unprotected infrastructure. If there is a change of occupancy to high-hazard content, auxiliary fire protection, including automatic sprinklers, automatic roof vents and fire protection of all structural steel, must be installed.

The game-changer

Open steel bar truss is a game-changer. A report of a steel bar joist truss should change strategy. Strategy should be changed to no roof venting and withdrawal of Firefighters from the interior. I was en route to a second-alarm fire and explosion in the Bronx, New York, and heard a radio report of a “truss roof.” I immediately interrupted the radio communication with an order, “Division 7 orders everyone off the roof and out of the building.” When I arrived in front of the fire building, the Officer came up to me and said, “Chief! Chief! This is only a small content fire. The truss or the structure is not involved.” I said, “Okay, let’s go look.” We went into the building and when I saw it was a content fire, I said to the Officer, “Okay, continue with the interior operations.” The lessons learned at this fire were early identification and reporting the presence of a truss as the keys to safety on the fireground.

Type II, Noncombustible/Limited Combustible Battlespace Casualties

South Carolina, nine Firefighters died in a Type II, noncombustible/limited combustible, heavily fuel-loaded furniture battlespace during flashover. NIOSH Firefighter fatality investigation F 2007-18

Chapter 23: Ordinary Construction Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


Type III ordinary construction is a battlespace full of snipers and booby traps. Hiding from view are unpleasant surprises that can defeat firefighting. The snipers and booby traps in Class III construction are concealed spaces, poke-through holes, pipe chases, suspended ceiling spaces and a massive void called a cockloft or common roof space. In this battlespace, Firefighters must be vigilant and always suspect hidden fire spread. In these hidden spaces, concealment and fuel feed fire spread that can break out from a wall, drop down from a ceiling or rise up from a floor.

Type III ordinary construction has been described as a lumberyard surrounded by four brick walls. It also could be called a honeycomb of concealed spaces surrounded by four brick walls. It is a difficult battlespace because the structure allows flame, heat, smoke and toxic gases to spread hidden from view. Also, unlike concealed spaces found in Type I or Type II structures, in Type III building voids, there is fuel inside these concealed spaces to feed a fire and make it grow.

In addition to hidden fire spread in the Type III battlespace, there is a collapse danger. Wood floors and roof burn and collapse, sometimes pushing brick walls outward, with parapets and coping stones knocked over by the power of hose streams. The following are more battlespace dangers of Type III construction.


Ordinary construction is not ordinary.

Type III ordinary construction sometimes is called brick and joist construction. It has become expensive to build and is being replaced by the more economical, Type II steel and cinder block buildings or Type V wood-frame structures, covered with brick veneer that looks like ordinary construction. A Type III building has masonry bearing walls supporting wood beam floors and roof; it is not veneer brick. The official building code name of brick and joist ordinary construction is Type III construction.

Roman numerals have been assigned to the five common types of construction

chapter image Fig. 23.1  Type III ordinary construction cockloft fire. Flames have spread to the cockloft through concealed spaces.

I fire-resistive; II noncombustible; III ordinary; IV heavy timber; and V wood frame. It is no accident that Type III is in the midpoint of the five common types of construction. One reason it is positioned here is because it has the medium amount of combustible wood in its structural composition. A Type III ordinary building has more wood in its infrastructure than Type I or Type II, but not as much wood structure as Type IV heavy timber and Type V wood frame.

Some Type III ordinary constructed buildings are a century old and must be renovated and the renovation process creates new fire hazard problems.

Five Types of Construction      Amount Of Structure Fuel
Type I: Fire-resistant Lowest
Type II: Noncombustible
Type III: Ordinary (brick and joist)
Type IV: Heavy Timber
Type V: Wood frame (brick veneer)    Highest
chapter image

A brick veneer building is not ordinary construction.

A brick veneer building may look like an ordinary constructed building, but it is not. There are no masonry walls in a brick veneer building. They are wood stud bearing walls covered with brick finish. In a Type III building, there are three types of masonry walls: bearing, non-bearing and party.

A brick, stone or cinder block bearing wall is defined as a wall that supports a weight other than its own. A non-bearing wall is defined as a wall that does not support any weight other than its own mass. A party wall is defined as a bearing wall that supports floors and roof beams of two adjoining buildings.

A Firefighter must know the difference between these kinds of walls when fighting fire in ordinary constructed buildings. For example, if there is a wall collapse, one wall--the bearing wall--is going to cause the collapse of any supported parts of the structure. A non-bearing wall may collapse and not cause other parts of the structure to collapse. This is because a non-bearing wall has fewer connections to a structure and a bearing wall can support all floors and roof of a building.

chapter image Fig. 23.2  Brick veneer structure is a Type V wood-frame building. A Type III ordinary structure has brick bearing walls. Veneer brick cannot be load-bearing.

A party wall is a bearing wall that supports the floors and roof of two buildings. A party wall can have the ends of wood beams of both buildings embedded in its masonry and when a fire occurs in one of the buildings, flames and smoke can spread through the masonry where the beam ends meet back to back. Small cracks and crevices and loose mortar near the back-to-back beam ends embedded in the wall may allow fire and smoke to spread through the eight- or 10-inch brick or cinder block party wall.

A party wall separating stores in a strip mall structure sometimes is mistaken as a fire division. A party wall is not a fire division. A party wall is built to support two adjoining buildings. A fire division is built specifically to stop fire. It does not support wood roofs or floors. A fire division is not a bearing wall. A party wall is designed to save money by serving two occupancies.

If you examine a party wall in the ordinary structure has brick bearspace below the roof and above the ing walls. Veneer brick cannot be ceiling, in addition to roof beams emload-bearing. bedded in the wall, you also may find many poke-through holes in the masonry wall. These openings, sometimes unauthorized and illegal, can spread fire between buildings or stores. If you pull a ceiling in an adjoining store during a fire in an exposure, you may discover large holes in masonry to run electric cables, air-conditioning ducts or plumbing pipes.


Never trust a party wall to stop fire. A true fire division wall is superior to a party wall. For example, it will not have floor or roof beam ends embedded in the wall. It is an independent structure with its own foundation. It has been tested in a laboratory to resist fire and given a three- or four-hour rating. A party wall separating a row of stores may stop fire spread. If it does, consider yourself lucky, because it is not designed to do this. Whenever you are expecting a party wall to stop fire spreading in a common roof space between stores or buildings, the ceilings on the exposure side must be opened and the wall integrity examined.

A parapet wall is a recurring collapse danger.

chapter image Fig. 23.3   Fire spread through this party wall in the pockets holding back-to-back roof beams.

A parapet wall is the portion of a wall that extends above the roof level. When you climb up to a roof, you may see a parapet wall around the perimeter of the roof, dividing the stores or building. A parapet wall keeps you from walking off the roof edge. A bearing wall, a non-bearing wall and a party wall in a Type III building can have a parapet raised section extending above the roof deck, which can be 12 inches or six feet high. A building code recommends a three-foot-high parapet, but some owners put a higher decorative parapet wall on the front of a one-story building to make it appear taller.

This parapet section of a wall is the weakest part of a wall. It is eroded by exposure to the elements. The parapet section extending above the roof is exposed to weather on three sides--top and both sides. A coping stone protects the wall top from moisture. A coating of tar and/or metal protects the unseen back and the front of the parapet can have a glazed, water-repellent finish. Over decades of exposure, rain, snow and ice can wash away the mortar between bricks and weaken a parapet section of a wall. A freeze/ thaw cycle causes small cracks in a parapet to widen. The freeze/thaw cycle begins when rain enters the crack in the wall and freezes. This expansion widens the cracks. When temperatures moderate and ice melts and washes out, so does the mortar.

After years, an old brick with mortar erodes and the wall will lean inward or outward and become unstable. In some instances, the mortar completely loses its adhesive qualities and bricks in the wall are resting on top of each other only by gravity. When this happens, the slightest impact from a hose stream, explosion, earthquake or strong wind can topple a parapet wall of a Type III ordinary constructed building.


In areas of this country where earthquakes are frequent, the building codes limit the height of the parapet wall on buildings. Parapet walls are the first part of a shaking building that collapses. People have run out of a building during an earthquake and been killed by a falling parapet wall. At fires, heavy-caliber hose streams, sweeping the top of a burning roof, have knocked coping stones or the entire parapet wall down on top of Firefighters.

chapter image Fig. 23.4   The most dangerous wall is a parapet over large display windows at the front of a one-story strip store.

The most dangerous parapet wall in the Type III ordinary constructed building is the decorative one at the front of a one-story strip store, rising over several large display windows. This wall is balanced on top of a steel I-beam, spanning the opening, and receives its support from the steel beam. During a fire, after the front windows are vented and flame blows out of the large show window opening, it heats the supporting steel I-beam, causing it to twist and warp, sometimes collapsing the parapet on top of Firefighters directing hose streams.

Walls can be categorized into three types: bearing walls, non-bearing walls and freestanding walls. Parapet walls are freestanding. An Incident Commander (IC) should know the relative stability and relative destructiveness of walls of an ordinary Type III building.

Stability of Walls

Wall Type      Stability
Bearing wall Most
Non-bearing wall
Freestanding (parapet) wall Less
chapter image

Destructiveness of Walls

Wall Type      Stability
Bearing wall Most
Non-bearing wall
Freestanding (parapet) wall Less
chapter image

Coping stones can be a deadly falling object or missile.

Every parapet wall on a Type III ordinary constructed building will be topped by a coping or capstone. A coping stone is designed to keep rainwater from seeping down into the top of bricks and mortar of the wall. Depending upon its composition, a coping stone can weigh between five and 50 pounds. When parapet walls are not properly maintained, mortar used to cement the coping stone to the wall top can lose its adhesive qualities. If this happens, the coping stone will become loose and can be knocked off the top of the wall easily.


Many old Type III buildings have coping stones along rooftops that merely rest on top of the wall. Coping stones can be knocked off a roof by sweeping master streams or retracting aerial platforms, snorkels or aerial ladders with the buckets dragging along the top of a parapet.

Firefighters have been killed by falling coping stones. Firefighters operating around the perimeter of a burning building must be aware of this danger. When retracting an aerial platform resting on a parapet coping stone, the chauffeur first should raise the ladder up, then retract it. Firefighters working around a burning building where master streams are operating should avoid the downstream area where the powerful water stream will drive roof fragments, such as chimney bricks, slate shingles, parapet walls and coping stones.

chapter image Fig. 23.5a   This pile of coping stones narrowly missed a Fire Officer supervising a hose-line stretch. A retracting tower ladder pulled a section of parapet down.
chapter image Fig. 23.5b   The coping stone was ripped from the parapet by a tower ladder retraction.

Concealed spaces and poke-through holes are a recurring fire spread problem in Type III ordinary constructed buildings. Every type construction has a specific, different, fire spread weakness, allowing flame to spread throughout the building. ICs must know these structural fire spread weaknesses to:

  1. Prevent fire spread from the area of origin
  2. Prevent Firefighters from becoming caught and trapped by fire spread.

The specific fire spread problem of Type III ordinary constructed buildings is its concealed spaces. There are voids, concealed spaces and poke-through holes behind every plaster wall, ceiling and floor through which flame and smoke can spread. These voids and poke-through holes are inherent in this type construction and Type V woodframe construction. These hidden spaces contain large amounts of combustible material--wood lath, wood furring strips, cross bridging, wood joists and two- by four-inch wall studding--feeding unseen combustion.

Fire sometimes originates inside one of these concealed spaces, but more commonly, a fire starts in content and burns through a plaster ceiling or wall, spreading into a concealed space. Once inside a concealed space, flames and smoke can extend throughout the entire structure, hidden from view and fueled by the interior combustible framework.

The largest concealed space in a Type III ordinary constructed building is a common roof space, the “cockloft.” This large, common roof space designed for insulation is found above the top-floor ceiling and below the roof. This common roof space extends over all the top-floor rooms or apartments in a Type III building and it can be several feet high. Sometimes, the common roof space is connected to the adjoining row structures and allows fire to spread over several connected townhouses, condominiums or row dwellings. A common roof space allows large, top-floor fires to spread over many connected structures, requires multiple alarms of Firefighters to extinguish and causes major water damage to lower floors.

chapter image Fig. 23.7   This concealed space goes from the cellar up to the cockloft.

Fire prevention codes address the problem of the common roof space in Type III and Type V wood-frame buildings, requiring “fire-stops” or fire barriers, subdividing the common roof area into subdivisions not more than 3,000 square feet. However, in communities without fire codes, there are no requirements and the common roof space is unrestricted, resulting in fires destroying entire condominiums, apartment houses or rows of dwellings.

Bathrooms are a floor collapse hazard.

This room is a collapse danger during a fire. A bathroom floor that has been rotted by moisture over years and overloaded with heavy fixtures is a collapse danger during a fire. Already weakened by rot and overload, flame and heat can cause sudden failure. The floor of a bathroom can collapse more readily than floors of other rooms because it supports a heavy “dead load.” Cast-iron tubs, sinks and porcelain toilets weigh thousands of pounds.


This heavy weight is concentrated in the smallest room of the building, supported by a few floor joists, and the finished tile floor of a bathroom also contributes to floor collapse. When a bathroom floor has a thick tile floor surface set on top of two or three inches of masonry, which may be on top of a sand bed, the supporting wood floor beams are reduced in size. This old-style tile floor, called “deafening boards” to facilitate sound reduction, may have the joists cut and reduced in depth to keep the bathroom floor level with floors in other rooms. Floor joists in the building may be two inches wide and 10 inches deep, with the bathroom floor joists two inches wide, but only four inches deep. During overhauling, direct the hose stream and pull ceilings from the doorway if it appears the bathroom floor is weakened.

Vertical fire spread in Type III buildings

Bathrooms and kitchens are the rooms that can spread fire to a floor above or several floors upward to the common roof space. Bathrooms and kitchens have concealed spaces containing water pipes, drains and air vent ducts that rise vertically from cellar to roof. Where the pipes pass through floors, there are poke-through holes and spaces that are not fire-stopped, allowing rapid vertical fire spread up these shafts and pipe chases.

Flames burning through a suspended ceiling can lead to a bathroom or kitchen and rise up through all floors. When fire is suspected to have spread from a bathroom or kitchen, up a pipe recess, an IC should have Firefighters check all floors above and the common roof space for fire spread.

When an old Type III ordinary constructed building has been renovated, new construction techniques often make concealed spaces larger and create many more of them, increasing the concealed fire spread problem. Also, much of the inherent fire-stopping created by the old construction techniques will be removed during renovation.

For example, excess plaster drippings that create unintended fire-stopping will be removed and wood bracing between wall and floor beams, acting as unintended fire-stopping that can slow fire spread, will not be installed. Flame and smoke in concealed spaces of a renovated Type III building will travel even faster than normal. Before leaving the scene of a fire in a renovated building, have a Fire Officer make a last-minute check of bathrooms and kitchen on the top floor, as flames in concealed spaces could have skipped floors and spread to the top floor and common roof space through larger and numerous concealed spaces.

Suspended ceilings are overhead traps that can ensnare Firefighters.

To make a Type III renovated building more energy-efficient, high ceilings are lowered. Now, each floor can have a suspended ceiling and the largest one will be the top-floor suspended ceiling. These suspended ceilings are attached to beams above by hanger strips of wood, wire or steel rods. A suspended ceiling is held up by the collective strength of all the hanger strips of wood or wire. If fire enters the common roof space and these supports are burned away, the entire suspended ceiling framework can collapse on Firefighters who are below, extinguishing a fire. Care must be exercised when opening up this suspended ceiling to check for fire. If too many Firefighters use pike poles and forcefully pull down on the furring strips instead of only the ceiling panels between the furring strips, the entire ceiling framework can collapse on top of them.


The “Fireman’s cut” is not our friend.

chapter image Fig. 23.8   The largest concealed space in a Type III ordinary constructed building is a common roof space of "cockloft."

Wood floor beams embedded in the masonry bearing walls of Type III ordinary construction may have the ends cut at a 45-degree angle, called a Fireman’s cut. Another name for a Fireman’s cut is a self-releasing beam. Self-releasing floor beams in Type III ordinary construction are designed to allow a floor to collapse without collapsing the supporting bearing walls. The cut beam ends can rotate out of the embedded masonry space and allow the bearing wall to stand. When a floor beam does not have a self-releasing beam end cut, the falling floor beams can topple the masonry bearing wall outward. The self-releasing beam end is designed to fail and save the more expensive masonry walls.

However, today our tactics have changed. This self-releasing beam protects Firefighters operating outside a burning building and, today, we fight fires from inside the the building. Also, some say it actually facilitates floor collapse and does not help Firefighters conducting interior operations. Perhaps it should be called a “builder’s cut” instead of a Fireman’s cut.

Open-joist construction fails faster.

chapter image Fig. 23.9   The Fireman’s cut is a self-releasing beam. The floor collapses and it saves the walls.

The first floor of a residence is usually openjoist construction. Typically, there is no ceiling on the underside of the first floor in a cellar. This makes the first floor more likely to collapse when there is a cellar fire. Some ordinary Type III construction commercial buildings are without plaster ceilings on every floor. Garages, storage buildings, warehouses and factories where the public does not enter, often do not have ceilings that protect the underside of floors from fire in Type III buildings.

A plaster ceiling can provide a one-hour, fire-retarding effect for the underside of a wood floor or roof from fire in the content below. Without a protective plaster ceiling, the interior structure ignites and is destroyed more quickly.


A Type III building without ceilings is called “open-joist construction” and it would be identified as a Type III 200 construction. If the Type III building interior was covered with plaster, the construction would be identified as Type III 211. The three Arabic numerals after the Roman numbers stand for the hourly fire protection rating of the

  1. Exterior walls
  2. Girders and columns
  3. Floors.

With a plaster interior, Type III 211 means the exterior walls have a two-hour rating; the columns and girders have a one-hour rating; and the floors have a one-hour rating. Open-joist construction Type III 200 can suffer early collapse of a floor or roof during a fire. When this construction is discovered inside the building, the IC should be notified.

chapter image Fig. 23.10   The first floor of a residence building can collapse more quickly during a cellar fire because the cellar often has no ceiling protection.

The exposed wood deck and beams of an open-joist Type III building can burn through more quickly and Firefighters searching above a fire may plunge a foot or leg through the burned or charred decking. Firefighters who have fallen through a burnedaway wood deck, search the floor above in an open-joist construction ordinary building and have been trapped with their lower torso, becoming wedged between the joists. Unable to quickly extract themselves, they have been seriously burned.

To avoid plunging through a burned-out floor deck in a Type III constructed building, crouching Firefighters advancing a hose-line stretched in front when moving forward to feel for a weakened floor. The weight of the body should be supported by the back leg beneath the Firefighter. Firefighters searching should use a tool to probe the floor ahead. These techniques will protect only against a deck collapse, not a floor beam collapse.

Type III ordinary construction building battle plan:

  1. After extinguishing a fire in a Type III battlespace, Firefighters must check for hidden fire by opening up ceilings and walls nearby.  
  2. If fire already has spread to the concealed spaces, check the cockloft; it may have reached there, too.
  3. When a decision must be made to break up a plaster wall and check for hidden fire, it causes property damage. Firefighters take an oath to protect life and property and sometimes are reluctant to do this. However, if property is not damaged and hidden fire is undetected, there is a danger of a smoldering fire reigniting after Firefighters leave the scene and destroying much more property and perhaps killing or injuring occupants.

When faced with a decision to damage property to check for hidden fire, Firefighters must follow the priorities of firefighting: life safety is the first priority; fire containment is the second priority; and property protection is the third priority. If you open the plaster wall and there is no fire, you made an error of commission and damaged property. But if you decide not to open the wall, leave the scene and there is a rekindle fire, you have made an error of omission and it may destroy the entire building and take a life. Most ICs, including myself, advise opening up the wall and checking for hidden fire in a Type III battlespace.

The game-changer

A game-changer is discovery of fire in a cockloft or a report of an unstable floor or wall. If cockloft fire cannot be extinguished by pulling top-floor ceilings and hose-lines, an outside aerial master stream will be used. A report of an unstable part of the structure should require the IC to consider withdrawal and defensive operations. For example, position aerial master stream apparatus for the cockloft fire, set up a collapse zone, have Firefighters flank the dangerous wall or use the repositioned aerial master stream directed from above the wall.

Type III Ordinary Construction Battlespace Casualty

Indiana, parapet wall of Type III battlespace collapsed on three Firefighters; one killed and two injured. NIOSH Firefighter fatality investigation F 2002-44

Chapter 24: Heavy Timber Construction Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


There is a joke in the fire service: “An engineer asks an architect what we should do with a heavy timber building that burns rapidly, overwhelms fire protection systems, forces Firefighters to flee for their lives, burns their apparatus abandoned in the streets and radiates heat across great distances, igniting nearby buildings.” The architect responds, “That’s easy. Let’s add glue to the timbers and build skyscrapers in New York City with it and call it cross-laminated timber construction (CLT).” Cross-laminated heavy timber buildings feature wood panels consisting of three to seven layers of dimensional lumber oriented at right angles to one another and glued to form timbers. This is another example of engineered wood, similar to lightweight truss wood beams and wood I-beams, small pieces of wood attached or glued together to form larger structural elements.

Of all the types of construction, a Type IV heavy timber building presents the greatest challenge to Firefighters. It has large open spaces, high ceilings and large, exposed wooden timbers that give an impression of an easy firefighting operation. Don’t be fooled. Operations can turn very bad, very quickly. For example, the large open space can allow flames to spread freely above and behind you, the high ceiling prevents you from sensing the severity of heat buildup above and if the timbers are soaked with oils from decades of lubricating factory machines, flames will spread with explosive speed and be impossible to extinguish with a hose stream.


The modern high-rise buildings they are planning can have glue-soaked timbers, instead of oil-soaked timbers. If a Type III ordinary constructed building is considered a lumberyard enclosed by brick walls, Type IV must be considered two lumberyards enclosed by brick walls and the old wood floor may be soaked with oil. This type construction has the second greatest percentage of structural fuel load of the five types of construction. Type V wood construction can be total wood inside and for the outside walls. Type IV can be total wood inside, but must have masonry exterior walls. However, builders want to add glue and build Type IV buildings higher.

chapter image Fig. 24.1   Worcester, Massachusetts, vacant, heavy timber, cold storage building fire killed six Firefighters on December 3, 1999.

Heavy timber wood interiors are a major firefighting problem. If the interior exposed wood structure becomes involved in flame, it can spread like lightning and require Firefighter emergency withdrawal. Additionally, it can require apparatus in the street to be abandoned or repositioned under cover of water streams and it can require Firefighters to protect exposed buildings across the street from radiation heat fire spread. This change in fire size can occur quickly.

The following are some facts about heavy timber Type IV construction. Firefighters must know how to successfully combat fire in this dangerous battlespace.

Vacant buildings

Many Type IV heavy timber constructed buildings across America are vacant and deteriorating. These were manufacturing buildings that now are closed. The passive, built-in fire protection is not working. Automatic fire doors are missing or blocked, fire doors have no closing devices and fire division walls have holes. And, the active fire protection--standpipes and sprinkler systems--also are out of service. Without these fire appliances, the Type IV buildings are deadly places when fire strikes.

chapter image Fig. 24.2   Two Philadelphia Firefighters were killed when a vacant, heavy timber building wall collapsed on an adjoining, one-story building they were searching, April 9, 2012.

Six Firefighters in Worcester, Massachusetts, were killed in a heavy timber, vacant building fire on December 3, 1999, and on April 9, 2012, two Philadelphia Firefighters were killed, fighting fire in a vacant, Type IV heavy timber building. After the massive fire was successfully extinguished, a huge, five-story, freestanding brick wall collapsed onto an adjoining, smaller, one-story building where Firefighters were searching. The collapse killed the Firefighters after the fire was under control.

There were several lessons learned at this fire. One was, even after a fire is under control, the battle environment remains deadly, where explosions, toxic gases, collapse and rekindle flash fires still can occur. Also, during a fire when walls of big buildings collapse on top of smaller, nearby structures, they crush the smaller building under tons of rubble. Adjoining buildings must be included inside collapse danger zones when withdrawing and defensive strategies implemented. These collapse danger zones must be maintained when walls appear unstable, even after the fire is under control. This 18-inch-thick, five-story brick wall, freestanding section remaining after floors and other connecting walls had collapsed, suddenly fell without warning in a curtain walltype collapse, straight down on the adjoining, one-story building.

When a Type IV heavy timber building in your community becomes vacant, the Fire Chief should conduct a pre-fire planning inspection preparing for a major fire. The building department should be notified and one of the following steps recommended:

  • The building be demolished
  • The building be renovated into a residence or business
  • The building be boarded up to prevent squatters and entry by children  
  • The building to be burned with a controlled, supervised fire

Wood size

Firefighters should know the building code description of a heavy timber construction differs from the other four types of construction. For example, with Type I, II, III and V construction, the Roman number is followed by three Arabic numbers that identify the hours of fire resistance for

  1. Exterior walls
  2. Structure framework columns, girders and trusses
  3. Floors

These Arabic numbers identify the hours of fire resistance required to protect them.

With Type IV heavy timber, it is different. Type IV construction describes structure framework and floors with letters, HT. These letters are intended to show they meet heavy timber requirements of size, not hours, of fire resistance. For example, the International Code, chapter 6, identifies solid or laminated wood. Type IV requires dimensions of columns not less than eight inches in any dimension; girders not less than six inches in any dimension; and trusses and arches supporting a roof and resting on top of a wall, not supporting a floor, shall be not less than four inches in width and six inches in depth. The letters HT indicate these wood sizes have been met.

Type I: Fire-resistant Type I - (3) (3) (2)
Type II: Noncombustible Type II - (2) (2) (2) or (0) (0) (0)
Type III: Ordinary Type III - (2) (1) (1)
Type IV: Heavy Timber Type IV - (2) (HT) (HT)
Type V: Wood frame Type V - (0) (0) (0)

Textile mill construction

chapter image Fig. 24.3   After the fire was declared under control, this wall collapsed on the one-story building.

Heavy timber sometimes is identified as “mill” construction, because these structures first were built in New England as textile mills. Later, they were used across the country for manufacturing because of the large, open floor areas. Heavy timber buildings were considered the first high-rise buildings. A heavy timber building could be five or six stories, much higher than ground ladders, and the floor area beyond the reach of Firefighters’ hose streams. These buildings were the first to have automatic sprinklers installed to protect workers and the building, which was the main commercial industry of a town. When a fire occurred in one of the large floor spaces, if Firefighters were unable to quickly respond, it would grow rapidly beyond the extinguishing capabilities.

chapter image Fig. 24.4   Wall collapsed on row of smaller buildings across the street.
chapter image Fig. 24.5   Big building collapses on small buildings.

Experience has shown that Firefighters with one or two large hose streams can extinguish up to 5,000 square feet of fire in an open floor space. This would be insufficient for 100 by 400 feet or 40,000 square feet. Automatic sprinklers are required for large open spaces of more than 5,000 square feet. The heavy timber buildings that have survived into the 21st century have been protected by automatic sprinklers.

chapter image Fig. 24.6   The columns on the first two floors are cast iron; the top two columns are heavy timber.

While sprinklers operate, Firefighters are needed to rescue people, extinguish small pockets of smoldering fire and overhaul to prevent rekindle.

High ceilings

High ceilings are a danger to Firefighters entering any large floor area. Ceilings of 12 feet or higher, required for large factory machines, allow fire to spread over the heads of advancing Firefighters. In some instances, oil used to lubricate machines soaks through the floor into the ceiling and flame can flow over the heads of Firefighters and outflank their advance.


The high ceiling creates a false are cast iron; the top two columns size-up of a fire because super-heat- are heavy timber. ed smoke flows over the heads of

Firefighters and when it flashes over, it then radiates down, burning Firefighters. High ceilings allow Firefighters to advance a great distance into a burning room and prevent accurate assessment of fire. Firefighters have one chance to extinguish a fire in a large, Type IV heavy timber building with a hose-line. If unsuccessful, they must withdraw because the growing fire will cause radiated heat waves coming out the windows and ignite buildings across a wide street. Eventually, floors will collapse after a long-duration fire and then the big walls come tumbling down.


The structure framework of a Type IV heavy timber building is exposed wood walls and a ceiling that is not covered with plasterboard. The wood columns, girders, truss and arches are unprotected and not covered with plasterboard, fire-resistive material. The thickness of the wood members is supposed to give the building an equivalent hourly fire resistance. Fire resistance in heavy timber construction is based on the estimated time it will take to burn and reduce the thickness of the structure to a point of failure. Structure bearing columns in some century-old Type IV heavy timber buildings are constructed of cast iron instead of solid or laminated wood.

Poorly manufactured cast-iron columns can have uneven thickness and non-uniform strength on all sides. This defect was discovered in several post-fire investigations. This defect in the cast-iron column occurs during manufacturing and cannot be detected during an inspection. Firefighters must notify the Incident Commander (IC) whenever cast-iron columns are discovered in a Type IV building. This information will influence firefighting strategy and save your life.

Structure fire load

There are two types of fuel load a Fire Officer must consider to evaluate a building’s fire hazard: the content fuel load and the structure fuel load, consisting of the structure itself. A heavy timber building provides the second greatest amount of interior structure fuel load of the five types of construction. Except for the exterior walls, a massive wood interior structure framing can create a fire that is impossible for any fire department to extinguish. Timber wood columns, wood girders, wood beams and wood floor and ceilings can provide more fuel to burn than the content in the building.

chapter image Fig. 24.7   The connections of a heavy timber building are unrestrained and come apart during fire.

During the life of a Type IV heavy timber building used as a textile mill or factory, there can be another hazard besides the massive wood; it is oil, used to lubricate textile and other machines to keep them working smoothly. Over the decades, the oil drippings of lubricants can be soaked into the three- or four-inch-thick floors. This oil adds to a massive, exposed wood interior and can make a fire spread explosively.

When attacking a small fire in content with the first attack handheld hose-line, the objective is to prevent flames spreading to the wood structure. If the massive wood interior of a heavy timber structure does become involved, strategy must change swiftly. Instead of an interior attack, Firefighters must withdraw from the building.

Fire spread by radiation heat waves

The recurring fire spread problem of Type IV heavy timber construction is radiation heat. The big advantage of a heavy timber Type IV building is no concealed spaces and that then becomes a big disadvantage. Plaster walls and ceiling do not exist, so there are no concealed small spaces, but when the massive wood structure burns and because the interior is not covered by plasterboard, it allows radiated heat waves to travel out of the many windows and spread across a wide street and ignite nearby buildings. No other construction type spreads fire like this.

Radiated heat is invisible. It can be felt, but not seen, and it quickly spreads fire to adjoining buildings. When strategy is being changed from an interior to a defensive exterior attack, if apparatus are repositioned farther away, radiation heat waves will prevent Firefighters from climbing back into the apparatus cabs to unhook pumpers and retract ladder stabilizers. After the abandoned apparatus are burned and blistered, they may be buried beneath massive collapsing walls.

Hierarchy of construction

During a major-alarm fire in heavy timber buildings, the burning floor sections collapse first, then the columns and girders fail and, finally, the walls tumble down. One of the important findings of the Boston Vendome Hotel heavy timber fire and collapse, which killed nine Boston Firefighters in 1972, was a concept of a structure hierarchy and how it fails during fire.

During the investigation, it showed there is a hierarchy in a building and the seriousness of a collapse depends on the first element in the hierarchy to fail. For example, if the column fails first, this is high on the hierarchy and so the collapse will be extensive. If a floor beam--low on the hierarchy—fails, the collapse will be serious, but not as devastating. Firefighters must know in any building construction the seriousness of a collapse will depend on the first structural element failing.

Hierarchy Construction Element
High Bering wall
Low Floor beam
chapter image

Surface to mass ratio

Firefighters also must understand the building construction concept of surface to mass ratio. A heavy timber building will be described by a fire protection engineer as having a low “surface to mass” ratio. What does that mean? A low surface to mass ratio means there is a low amount of burnable surface area of wood for the total mass of wood in the structure.

For example, heavy timber structure has a low surface to mass ratio and takes a long time to be consumed by flames. On the other hand, a lightweight wood truss building has a high surface to ratio structure and can burn rapidly. Another example of how fire ignition varies by the surface to mass ratio is if you cut a large timber to small pieces (toothpicks), you increase the surface to mass ratio. If you had a blowtorch and applied it to a timber, it would take some time to ignite, but the same timber cut into toothpick-sized pieces would ignite more quickly.

Masonry wall collapse

After a long-duration fire in a Type IV building is extinguished, the floors and framing will have collapsed during the blaze and the freestanding walls become a collapse danger. The massive walls of a heavy timber building can be two feet of brick thickness and weigh several tons. When these massive exterior walls collapse on the roof of adjoining buildings, they crush the smaller building.

When a brick enclosing wall falls at a 90-degree angle, it can cover the ground a distance equal to the height of the falling wall; bricks and stone can roll out much farther. Sometimes, people in buildings adjacent to or across the street from a burning heavy timber structure must be evacuated because of this danger.

chapter image Fig. 24.8   The large, open spaces of a heavy timber floor are beyond the reach of Firefighters' hose streams.

In Philadelphia, in 2012, Fire Lieutenant Robert Neary and Firefighter Daniel Sweeney were killed by a collapse of a masonry, five-story Type IV wall while they were searching inside a nearby, one-story building. Tons of falling bricks broke through the roof and buried the searching Firefighters in the building next door. There is always a danger of big buildings falling and crushing small, nearby buildings. This is especially true after a fire has been extinguished and the interior has burned and collapsed. The collapse that killed the Philadelphia Firefighters occurred 30 minutes after the fire was declared under control.

Firefighters must know the collapse danger of a burning building becomes greater the fire burns. The greatest collapse danger is after a fire because:

  1. The fire has destroyed the infrastructure--columns and girders.  
  2. The force of the powerful water streams used to extinguish the fire has weakened the masonry walls.
  3. There is a buildup of water weight absorbed into wood and plaster on floors that can increase the dead load.

Defensive firefighting strategy

Because a fire in a heavy timber building can be large and differs from other construction types, you should pre-plan a master stream firefighting strategy. The fire service is effective with small, handheld stream fire operations and not as effective with large aerial and ground master streams.

chapter image Fig. 24.9   Radiated heat waves ignited the facade of the building across firefighters from repositioning the apparatus.

One of the first considerations when planning to set up master streams at a burning heavy timber building is water supply. You must have hydrants supplied by eight-inch mains fed in a grid system—two-way supply--to supply master streams for Type IV burning buildings. Hydrants on dead-end mains will not provide extinguishing ability. Hydrants that are close to the building inside a collapse danger zone cannot be used during a major fire. Overhead street pole wires can impede positioning of aerial streams. Radiation heat waves emanating from windows can ignite nearby buildings or woodlands. Walls of a timber building eventually will collapse and they can fall out a distance equal to their height. An IC must set up a collapse danger zone of one or two times the height of the wall.

Initial attack

You have one chance to extinguish a fire in a Type IV heavy timber battlespace. The first attack hoseline must be able to extinguish the fire and a second line must be in place to protect the Firefighters’ escape. If the first attack fails, expect to see the biggest fire of your career.

Oil-saturated timbers

The wood timber columns, girders, trusses and floors of Type IV buildings often are saturated with oil that has been used for decades to lubricate textile or manufacturing equipment. This saturation with combustible oil creates a rapid flame spread along the underside of floors/ceilings, which can trap Firefighters.

Cross-laminated timber (CLT)

New York City is planning to build a high-rise building of cross-laminated timber construction. The National Fire Protection Association is calling for scientific, full-scale testing, stating this type of construction can contribute greatly to the structure’s fuel load, increase the initial fire’s growth rate and overwhelm fire protection systems, resulting in increased fire spread and increased danger to occupants, Firefighters, the building itself and neighboring buildings.


A heavy timber building battle plan:

  1. Stretch a large-diameter hose-line to the seat of the fire and extinguish the fire.
  2. Stretch a second large-diameter hose-line to back up the first line.
  3. If two hose-lines cannot extinguish the fire and it continues to spread, notify Command and evacuate occupants and withdraw Firefighters. Start moving apparatus back from the building before radiated heat prevents Firefighters from doing this.
  4. Protect exposures.

The game-changers

A game-changer is a report from operations that flames are overwhelming Firefighters’ hose streams and the recommendation should be made to withdraw. Oher game-changers at a heavy timber fire are a report that columns and cross-laminated timber construction are made of cast iron instead of timbers. The IC must prepare for defensive operations, withdraw occupants and Firefighters, reposition apparatus, protect exposures and prepare for severe radiation heat waves and structure collapse.

Type IV Heavy Timber Battlespace Casualties

Worcester, Massachusetts, six Firefighters overcome by smoke and fire in Type IV heavy timber storage building. NIOSH Firefighter fatality investigation F 99 F47

Chapter 25: Wood-Frame Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


A wood-frame building presents a two-front battlespace; fire on two fronts--inside and outside. A wood-frame building is the only one of the five types of construction that has combustible exterior walls. A two-front battlespace can develop when a room fire spreads out a window and up an exterior wall. Firefighters now have an inside firefighting battle and also must stop an outside wall fire.

A wood-frame building has all the concealed space fire problems of a Type III ordinary constructed building, in addition to the outside walls burning. From a fire spread point of view, this building presents the most difficult battlespace of all five construction types.

There are four common construction methods of a Type V wood-frame building:

  1. The braced-frame method, sometimes called post and girt or post and girder. This construction method was used to build three- and four-story wood buildings in the 19th century along the east coast.
  2. Next, wood-frame balloon construction also became a popular method for two-story wood buildings in communities where large timbers were unavailable.
  3. The 20th century saw development of a platform frame construction method, which became the most common method used to build residence buildings.  
  4. chapter image Fig. 25.1   Fire spreading on two fronts--out of a window and up a combustible wall to eaves–and into the common roof space.
    The last half of the 20th century came up with the lightweight wood truss method of construction using sheet metal fasteners instead of nail. This, unfortunately, has become the most popular, low cost and most dangerous wood-frame battlespace in America. Two big dangers are rapid fire spread and rapid collapse.

The following is a detailed examination of the four Type V woodframe building battlespace fire and collapse dangers.

Braced frame

A braced-frame wood building, also called “post and girt” construction, is one of the four ways Type V wood buildings can be constructed. This type construction was used to build three- and four-story Type V wood buildings. Most wood buildings used for residences are one and two stories in height. When buildings are higher, they require bracing with large timber members. Timbers more than four inches thick are used as corner posts and girders in the three- and four-story, braced-frame structures, along with two- by four-inch wood studs.

chapter image Fig. 25.2   Braced-frame construction also is called post and girt. The corner post is a mortise opening with a tenon inserted.

One of the problems with bracedframe construction using timbers is the mortise and tenon connection used to fasten them together. The mortise and tenon actually weaken the timbers and during a fire, the timber connections can fail. When fire weakens the structure, the timbers come apart and the entire three- or four-story building can collapse. Floors pancake down on one another and, simultaneously, enclosing walls fall outward and collapse in an inward/outward fashion. A mortise and tenon connection actually weakens the timbers when a mortise hole is cut in a corner post and a girder is reduced in size at each end to form a tenon tip.


The balloon construction

The balloon construction method is another way Type V wood buildings can be built. This type construction has a fire spread defect. It allows fire to spread up through exterior wall wood studs from cellar to attic. This construction method is used when building one- and two-story Type V wood buildings. Exterior walls of balloon construction are constructed with continuous, 20- or 25-foot-long, two- by four-inch wood studs.

For example, four exterior walls can be tilted up from the ground to form the four vertical enclosure walls. They are connected together at the corners. The fire problem is the four enclosure walls have a continuous concealed space extending from the cellar foundation walls up to the attic in which fire can spread. Also, if fire burns through a ceiling of the first or second floor, it can extend to an outer wall, then up to the attic through these concealed areas.

chapter image Fig. 25.3   Balloon construction exterior wall concealed spaces extend from cellar to attic.

When a balloon-constructed building is renovated with add-on rooms, exterior walls can become interior walls. Fire entering any wall of balloon construction may have spread up to the attic.

Firefighters must inspect buildings during construction to determine the type of construction and record and enter this valuable pre-planning information into computers for distribution to first responders. Other methods of determining construction methods for fire pre-planning information is through study of local building codes; fire insurance company maps; and when overhauling during a fire, Firefighters can observe exposed construction parts of a building.

Platform construction

Platform construction is a third method of constructing a Type V wood building. This construction method has no mortise and tenon connections that can break during a fire and no concealed spaces between exterior wall studs that can spread fire more than one story.


Platform wood-frame construction is superior to braced-frame and balloon wood construction from a fire protection point of view. When constructing a multi-story wood building using platform construction, one wall level is constructed, the floor is installed and then the next wall level is constructed on top of the floor. There are no spaces between exterior wall studs that extend more than one level. At the top of each level of exterior wall studs is a horizontal wood member called a plate, which acts as a fire-stop, preventing flame and smoke in a concealed exterior wall space from spreading vertically to the floor above. On top of the horizontal plate, the second-floor beams are placed and on top of this, the second-floor sub-floor is nailed. This horizontal wood member (plate) is an integral part of platform construction and can be relied upon being in place to stop fire from spreading from one story to the story above. Unlike a firestop that is required by law, this plate fire-stop is “inherent” or built-in fire-stopping.

However, there is one concealed space in platform construction that allows vertical fire spread and must be checked by Firefighters. Firefighters must check bathroom and kitchen voids and poke-through holes for vertical fire spread in concealed spaces. In these rooms, the most serious vertical fire spread can occur. Pipes and drains extend from cellar to attic, up poke-through holes inside concealed spaces. Knowledge of wood construction tells Firefighters they must open up ceilings and walls around pipes and drains when checking to ensure fire has not spread vertically. These vertical utility pipe and drain concealed kitchen and bathroom voids exist in balloon and bracedframe construction and must be checked for vertical fire spread.

Lightweight truss

chapter image Fig. 25.4   Platform construction with inherent fire-stopping plate on top of stud wall.

The fourth and newest method of Type V wood-frame construction is lightweight wood truss construction. This construction method is actually platform frame construction. However, floor and roof beams are not solid timbers, but parallel chord and inclined plane (gable peaked roof) trusses. This construction is inferior compared to braced-, balloon- and platform-frame construction because of the substitution of trusses, instead of solid-beam floor and roof joist construction.

There are two problems with the use of truss construction

First is rapid fire spread. Fire will spread much faster in this construction method if it penetrates a ceiling or floor space. Flames can spread parallel and perpendicularly to the direction of the floor or roof beams. Fire spreads perpendicularly through the open-web sections of the truss, as well as in a parallel direction. With solid-beam construction, flame would be partially blocked from spreading perpendicularly. A Fire Officer must realize there can be 100 percent faster fire spread in a truss-constructed Type V wood building when it involves the structure in a concealed space.


This rapid fire spread defect of wood truss construction often is overlooked because of the second problem truss construction presents. There is a rapid collapse danger in a wood building using lightweight trusses. Truss floor and roof beams are small pieces of two- by three- or two- by four-inch wood, connected together by inferior connectors called “sheet metal surface fasteners.” These sheet metal surface fasteners are inferior connections when compared to nails or mortise and tenons. This is because sheet metal surface fasteners penetrate only the surface of the wood ¼ to ½ inch. During a fire, the sheet metal surface fasteners quickly fail; they warp, buckle, pull away and fall from the truss pieces and allow the truss to come apart.

Underwriters Laboratories (UL) fire experiments and fire experience states truss construction can fail within five to 10 minutes. The sheet metal surface fasteners pull away and fall from the truss joists, even before the roof deck is destroyed by fire. Firefighters are used to the roof deck failing first, before the support beams. During an attic fire, truss supports fail first, then the deck fails. With solid-wood beam construction, the roof deck fails first. When a deck fails, solid-beam support can save Firefighters from falling all the way through the roof into the fire below. This is not the case with lightweight truss roof or floor construction.

Bearing walls

chapter image Fig. 25.5   Lightweight wood truss construction is a house of sticks.

Bearing walls on Type V construction burn. A Type V wood building is the only one of the five types of construction listed in the international building code that can have fire spread on its exterior walls. The other buildings–Type I, II, III and IV–must have brick, steel or glass exterior walls. With Type V wood construction buildings, the load-bearing walls can be destroyed by fire. The walls on a Type V building can be combustible wood shingles, wood planking or an oil-based product, such as asphalt or tar imitation shingle.

Fire coming out a window from the interior can spread up these combustible outside walls and Fire Officers must be aware of this possibility of fire going into the eaves and attic space. Even a small rubbish fire at the base of a Type V building quickly can spread up the siding into the attic. And, radiated heat from a nearby burning building can ignite the entire side of a wood building. There have been instances when the asphalt imitation brick siding of a building has been ignited and as the flames spread upward to the eaves, flaming droplets rained down the side of the building, fell into a window well and spread fire into the basement.


You have up and down fire spread. The exterior surface of a Type V wood building must be considered the seventh side of a fire and it must be checked for fire spread, along with the usual six sides: above, below and the four sides of a room fire. At a wood building, an Incident Commander (IC) may have to position a hose-line, deck pipe or ladder pipe around the outside to stop exterior fire spread at the same time an interior attack hose-line is stretched inside to combat fire. This feature of Type V combustible exterior walls may seem obvious to most Firefighters, unless you are a Firefighter who works in a district that has only ordinary or Type I or II buildings and then gets transferred into a suburban area, with mostly Type V buildings, as I was.

Concealed spaces

chapter image Fig. 25.6   A wood-frame bearing wall destroyed by fire and bout to collapse.

Wood buildings have voids, concealed spaces and pokethrough holes that are filled with combustible fuel, such as wood lath, wood furring strips, wood beam bracing, wood hanger strips and wood studs. Similar to a Type III building, there is a lumberyard of wood inside the concealed spaces of a Type V building.

For example, to cut off fire in a concealed space between floor beams, Firefighters go to the floor below to pull ceilings. And, when cutting a wood floor to get at a fire in between floor beams, start where the beams terminate near the bearing walls. Open here and work back to cut off the fire. If fire is discovered in a wall concealed space, pull the ceiling directly above the hot spot and work back down the wall to get ahead of any fire spread. If fire is discovered in a ceiling concealed space, go to the floor above and check to ensure that fire has not already spread here.

Fire in a concealed space must be stopped from spreading before it is extinguished. Type V and III buildings are a honeycomb of concealed spaces and they sometimes lead to the attic or common roof space. After extinguishing a room and content fire and it spreads to the attic or roof space through concealed spaces, you have failed in your fire extinguishing strategy. To be successful, Fire Officers must understand the concealed space fire problem in Type V and III building construction.


Connections count.

When a wood-frame burning building fails during a fire, check the nearest connections and you will find the cause. How the builder fastens the wood beams, girders, columns and bearing walls together matter.

There are three kinds of connections used in Type V wood-frame buildings: mortise and tenon connections, iron nail connections and sheet metal surface connections. Mortise and tenon connections are used in braced-frame, post and girt construction; nails are used in balloon and platform wood-frame construction; and sheet metal surface fasteners are used in lightweight wood truss construction.

The connection can determine how a wood building fails during a fire. For example, the mortise and tenon connection breaks at the point of connection because the column or girder has been weakened at this point by the connection itself. A column could have a hole cut into it to form the mortise opening. This connection point is where the column will fail. It is the weakest point. Girders or beams have had the ends reduced in size to form a tenon tip or holes to form mortise openings. This connection point is now the weakest part of the timbers. When a braced-frame building fails at a mortise and tenon connection during a fire, there can be a global collapse of the wood building. The entire structure fails: the four walls collapse outward and simultaneously all floors pancake down. This so-called inward/outward wood-frame building collapse is caused by failure of the mortise and tenon.

Nails used in balloon and platform Type V construction are the best connector from a fire protection point of view. A three- or four-inch nail does not weaken the wood members and it deeply penetrates the wood member at the connection. When compared to mortise and tenon and sheet metal surface connections, iron nails are superior connectors.

chapter image Fig. 25.7   A sheet metal surface fastener penetrates wood only 1/2 inch. We want nails!

The sheet metal surface fastener is an inferior connection. This thin piece of sheet metal is a dangerous connection during a fire and it is used only with lightweight wood truss Type V construction. This connection fastens the surface of the wood and when the wood burns and chars, the sheet metal fastener falls away quickly. When the thin piece of sheet metal is heated by a fire, it warps or curls up and pulls away from the wood surface. A lightweight wood truss is a structural composition of two- by four- or two- by three-inch pieces of wood and it depends on the connections to hold it together. Top chords, on the bottom chords and web members are held together by these inferior sheet metal surface connectors, which penetrate only ¼ to ½ inch in depth. When the connections fail, the truss fails. Fire experiments by UL and fire experience have shown the truss with sheet metal connections can fail within five to 10 minutes after arrival at the fire.


Peaked roofs

Wood buildings have peaked roofs. Fire Officers must know the construction features of a peaked roof. A peaked roof is rarely built on Type I, II or IV building construction. It sometimes is used on Type III buildings, but a peaked roof is most commonly built on a Type V wood-frame building. A peaked roof has primary and secondary structural members in its construction. A primary structural member supports another structural member and a secondary structural member does not. Bearing walls, columns and girders are primary structural members of a building. Peaked roof primary structural members are ridge rafters, hip rafters, curb rafters, collar beams and plates atop bearing walls. A roof rafter is considered a secondary structure member of a peaked roof.

Fire Officers must know which parts of a building are primary structural members, where they are located in the roof construction and ensure that Firefighters in their command do not to cut them when roof venting. If a primary structure member is cut or destroyed by fire, this could result in a progressive collapse--a collapse of one structure that causes the collapse of another structure member. If a Firefighter cuts a primary structure of a peaked roof with a saw during roof venting, it could collapse another structure member in the roof.

There are four widely used types of peaked roofs found on wood buildings--gable, hip, gambrel and mansard roofs. A gable roof has two sides sloping up from two bearing walls. A hip roof has four sides sloping up from four bearing walls. A gambrel roof has two slopes on each of two sides; the lower slope is the steeper slope. A mansard roof has two slopes on each of four sides; the lower slope is the steeper slope.

Primary structure members are located at different places on each of these roofs and a Fire Officer must know where they are to ensure they are not cut with a saw during roof-venting operations.

Primary structure members built into a common gable roof are the ridge rafter at the peak and a plate, which is a horizontal member atop a bearing wall. The gable roof rafters are supported by the plate on top of the bearing walls and the ridge rafter at the peak. These primary structure members are critical for roof stability and should not be cut. A hip rafter has nine primary structure members: a ridge rafter, four hip rafters and four plates atop the four bearing walls. A gambrel roof has five primary structure members: the ridge rafter, two “curb rafters” (horizontal members located where an upper roof slope changes direction to the lower slope) and two plates atop the bearing walls. A mansard roof is actually one hip roof atop a lower hip roof and there can be 17 primary structure members in this roof--a ridge rafter, four hip rafters on the top section, four curb rafters at slope change, four hip rafters on the lower section and four plates atop four bearing walls.

There is another primary structure member used in all of the above types of peaked roofs--sometimes found underneath a sloping roof--in an attic; it is called a collar beam. A collar beam is a horizontal beam connecting opposing rafters, designed to help resist the outward thrust of the roof rafters at the eaves or plates. If this collar beam is destroyed by an attic fire or cut during overhauling, it could weaken the sloping roof rafters.


Exterior veneer

Masonry veneer added onto wood building walls destabilizes the structure. Brick veneer, imitation brick stucco and fire escapes can overload wood building walls. Wall overload of Type V wood buildings must be considered in a Fire Officer’s size-up. Some old wood buildings are covered over with a brick veneer or imitation brick stucco to make them look new. Both of these coverings can conceal a major structural weakness, such as windows out of plumb, bulging walls or large cracks in wood walls. When a fire occurs, a Fire Officer mistakenly could think it is a Type III brick and joist ordinary constructed building, instead of a Type V wood-frame building.

Imitation brick stucco also adds dead load to the building walls and if they start to pull away from the building during a fire in an inward/outward collapse, this excess weight can accelerate failure. These enclosing masonry walls also can confine heat and flame to the interior of the structure.

A fire escape is another wall overload added to the walls of a renovated Type V wood building. The weight of a heavy metal fire escape bolted to the walls of a wood building make the wall unstable and vulnerable to collapse during a fire. The walls of a wood building can be two by four inches and a heavy metal fire escape in the form of a cantilever beam–a beam supported at one end–can destabilize the wall. This cantilever fire escape weight can pull a wall outward during a fire. Even if there is no fire, the weight of the fire escape can cause the designed stress and load of a bearing wall to change over years by pulling it outward. The add-on weight attached to the outer wall can change the builder’s designed axial load–centered or evenly distributed load of the two- by four-inch wall, to an eccentric load–a load that is off center or uneven within the two- by four-inch wall. When a fire occurs in a wood building, any wall that has a fire escape attached to the side must be considered unstable.

chapter image Fig. 25.8   Masonry imitation brick placed on woodframe building wall adds tons of dead load.

There is no reinforcement of wood bearing wall thickness. When a triple-decker wood building is constructed, the bearing walls are the same thickness for the full height; the lower story walls are not increased in size for additional reinforcement support. With masonry, brick and joist buildings, bearing walls are thicker at the foundation than at the upper level. A brick bearing wall can be 18-inch-thick brick at the foundation and taper to eight inches at the top-floor level. When a wood building is one or two stories, this lack of reinforcement may not be important. But when a wood building is three or four stories, the lack of reinforcement creates overload at lower floors. A triple-decker, Type V, wood-braced frame building will feature first- and top-floor bearing walls of the same two- by four-inch thickness, with no compensation for the greater load-bearing stress of the lower levels.

For example, say each level of a three-story wood building floor weighs five tons. We can have the third floor two- by four-inch-thick bearing walls supporting five tons; the second floor two- by four-inch bearing walls supporting 10 tons; and the lowest floor two- by four-inch bearing walls supporting 15 tons. There is no compensation of wall thickness for the greater load supported by the lower floors as in a brick building.

A wood-frame building battle plan:

The combustible exterior wall is a second front of a Type V wood-frame building battlespace fire. An IC always must be ready to fight a second front exterior siding fire if flames spread out a window up the side of a building. If this fire is not extinguished, it can spread to the common roof space and attached adjoining buildings.

There is a saying in the fire service; there are six sides to a fire:

  1. Above
  2. Below
  3. Side A
  4. Side B
  5. Side C
  6. Side D.

Incident Commanders who work in Type V wood-frame districts add to this saying; a seventh side of a fire--the exterior walls.

The game-changer

A game-changer in wood construction is fire spreading in concealed spaces of balloon construction, in a cockloft or up an outside wall, heading to the eaves or cockloft. The IC must open up nearby concealed spaces after a fire knockdown, have the attic or cockloft examined when there is balloon construction and ready an outside hose stream to stop an outside wall fire. If you receive a report of truss or wood I-beam floor or roof construction, it must be determined if the fire involves only the content or these lightweight structures. If it is the structure, a defensive fire strategy should be ordered.

Type V Wood-Frame Battlespace Casualty

Texas Firefighter conducting primary search in Type V wood-frame building killed in collapse. NIOSH Firefighter fatality investigation F 2013-17

Chapter 26: Chronic Fire Spread and Collapse Battlespaces

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


First, let me say that any building can spread fire or collapse in many different ways, any time, at any fire. However, that said, there are chronic fire spread and collapse patterns suffered by all of the specific five types of building construction examined in the prior chapters. These recurring fire spread patterns and repetitive structure collapse similarities have been identified in the five types of building construction during fire investigations.

There are construction defects in the five types of construction that allow fire to spread easily and there are construction weaknesses that allow building types to collapse readily when inovlved in fire. This chapter examines the recurring fire spread weakness and collapse similarities of the five types of construction of the five preceding chapters: Type I fire-resistive construction; Type II noncombustible/limited construction; Type III ordinary construction; Type IV heavy timber; and Type V wood frame. This information can help an Incident Commander (IC) be proactive and plan for a sudden fire spread or structure failure during a fire.

I. Chronic fire spread

Type I fire-resistive construction

There are five recurring ways fire spreads in a fire-resistive building:

  1. The most common fire spread problem here is auto-exposure, window-to-window, when flame comes out a window and spreads into an open or broken window above.  
  2. Another recurring problem of smoke spread in a Type I building with a central air system is through air ducts. During a fire on one floor, smoke can travel to several floors in a fire-resistive building through ducts of a central air-condtioning system.
  3. Another common recurring fire spread problem that must be checked is a small space located around the perimeter of a building between the outer edge of a floor deck and the inside of a curtain wall.
  4. A new international fire spread problem occurring in fire-resistive buildings is the exterior insulation finish system (EIFS), which is extremely combustible and spreads fire quickly up the exterior facade of a building. The exteriors of new high-rise and low-rise buildings are being renovated using flammable plastic insulation behind exterior metal cladding. This allows rapid flame spread over exterior wall surfaces.
  5. Finally, there is a rare fire spread problem in a Type I building that can occur at a serious, long-burning fire when a ceiling fails and the fluted metal floor above is heated and sags downward. This distortion can cause the two inches of concrete above to crack and allow small tongues of flames to spread through the floor.
chapter image Fig. 26.1   Auto-exposure, flame spreading from window to window, is one of the chronic causes of fire spread in the Type 1 fire-resistive battlespace.

An IC will be able to detect and take action to combat fire spread outside a building for window-to-window or exterior cladding when at the Command Post and quickly position an outside master stream to stop this. To reduce smoke spread through air ducts, upon arrival, an IC must order management to shut down any central air system. After a fire is extinguished, Firefighters must search all floors connected by the air system ducts, looking for accumulations of smoke or smoke-injured occupants. When fire occurs near the perimeter of a building, after extinguishment, Firefighters must be ordered to check the curtain wall concealed spaces in the vicinity.


Type II noncombustible construction

The recurring fire spread in Type II noncombustible construction is a roof fire. The roof deck covering a fluted metal roof is combustible. The roof covering can be several layers of asphalt between flammable paper and plastic.

For example, there can be a layer of asphalt, a layer of insulating paper, another layer of asphalt, a layer of plastic and then, another layer of asphalt and gravel. On some noncombustible buildings, there can be tons of asphalt built up on a metal roof. Asphalt is not tar. Tar is derived from coal; asphalt is derived from crude oil. Asphalt, a dark brown or black substance, has a flash point of 450 degrees Fahrenheit and an auto-ignition temperature of 600 degrees Fahrenheit. To reduce the total amount of asphalt when constructing a roof, the asphalt should be “strip-mopped” only over the seams of the fluted metal sheets, instead of covering the entire roof area. Strip-mopping greatly decreases the amount of crude oil derivative–asphalt on a roof.

An IC can stop an asphalt roof fire in a noncombustible building after every fire if Firefighters examine the underside of the fluted metal roof for charring or burning. Sometimes, heat can be conducted through the metal roof and ignite the asphalt roof covering. In other instances, the roof can be ignited if a small flame spreads through a seam of a fluted metal roof. If any one of these signs exists, Firefighters should be sent to the roof to check the asphalt roof covering for fire extension and open the roof covering at this point if necessary.

Type III ordinary construction

Recurring patterns of fire spread in a Type III ordinary constructed building most often occurs in concealed spaces inherent in woodframe construction. An x-ray of this so-called “lumberyard enclosed by brick walls” reveals a honeycomb of voids behind the walls, floors and ceilings of the structure, all creating small spaces in which fire and smoke spread.

chapter image Fig. 26.2   Combustible roof deck is the recurring fire spread problem of the Type II noncombustible/limited combustible battlespace.

If not discovered quickly after a fire is knocked down, a concealed space fire can spread quickly. Many of the concealed spaces in a Type III building lead up and terminate into the largest concealed space–a cockloft or an attic space. If fire reaches this large concealed space, it is likely the building becomes a total loss. An IC must check for a recurring concealed space fire as soon as a blaze is knocked down.


An IC’s strategy to stop a concealed space fire is to order Firefighters to open the ceiling above the fire and check at this location. Then, Firefighters must check behind the nearest wall for concealed space fire extension in the stud spaces. If necessary, check to ensure fire has not dropped down into the floor space. A thermal imaging camera can assist in this search for a concealed space fire.

Type IV heavy timber construction

chapter image Fig. 26.3   Fire spread from floor to floor in concealed spaces of a Type III ordinary brick and joist battlespace.

The good thing about Type IV construction is that there are no concealed spaces because there are no plaster walls or plaster ceilings that create these small voids. And there is no big concealed space called a cockloft on the top floor. Instead, the wood structure of a Type IV building is an open frame. The building interior is exposed. This absence of concealed spaces is a great advantage during a fire.

However, it becomes a disadvantage if flame spreads across the exposed wood walls, ceilings and underside of the roof. If the exposed wood structure becomes involved in the fire and cannot be extinguished with hose streams, there will be large quantities of flame and heat generated. The exposed bare wood will burn violently, spread out of the building and create the recurring pattern of fire spread of a Type IV structure--radiated heat fire spread. This exposed wood interior flame front can spread out the many windows and radiate heat great distances across a street and ignite nearby buildings. Radiated heat is the recurring fire spread of a Type IV heavy timber building.

To combat this type of recurring radiation fire spread, an IC should take several actions. First, he or she must closely monitor the initial interior attack progress. During the initial attack, detailed and frequent progress reports must be requested from an Operations Officer inside, specifically questioning the progress, success or failure of Firefighters advancing on the fire. At the first sign the interior fire is not going well, preparations for withdrawal and defensive firefighting strategy must be initiated.


Civilians, Firefighters and apparatus must be repositioned away from the building. Streets around the building can become untenable due to radiation heat waves coming from windows. Pumpers and ladders may have to be repositioned before heat makes it impossible for Firefighters to re-enter cabs to disconnect pumpers from hydrants and retract ladder stabalizing jacks for moving. Million dollar fire apparatus have been abandoned at Type IV building fires due to heat blistering, burning and being buried beneath tons of brick wall collapse. Occupant and Firefighter safety are the number one priority and exposed buildings will have to be protected with hose streams while the fire building burns.

Type V wood-frame construction

If Type III is called a lumberyard enclosed by four masonry walls, Type V construction can be described as a lumberyard enclosed by four combustible wood walls. This construction, similar to Type III, has a recurring fire spread pattern from concealed spaces located behind walls, above ceilings and below the floors. And, it also has a severe combustible exterior wall fire problem. The combustible wood or asphalt exterior siding spreads fire on the outside over and over.

chapter image Fig. 26.4   Radiated heat spreading across the street and preventing the repositioning of the tower ladder is a chronic fire spread problem of the Type IV heavy timber battlespace.

Again, there is a saying when checking for fire spread in most buildings. There are six sides to check for fire spread--the four walls and above and below. With Type V construction, there is a seventh side of a fire--the exterior walls. Fire can spread out a window and extend up the exterior of a wood building.

To prevent fire spread in a Type V building, an IC must cut off fire in the concealed spaces and also stop the outside wall fire. The combustible exterior walls of a Type V wood-frame building are called the seventh side of a fire. When combating a wood building fire, an IC must consider the use of an outside hose stream, deck pipe, portable deluge nozzle or tower ladder to stop any outside extension fire, in addition to the inside hose-lines to stop fire in concealed spaces.


Battle plans for chronic fire spread in battlespaces:

chapter image Fig. 26.5   Exterior wall fire is a chronic fire spread problem in a Type V wood-frame battlspace.
  1. In a Type I battlespace, be proactive and raise an aerial or aerial platform to stand by to stop auto-exposure or combustible cladding fire. The defend in place strategy is not an option during a combustible cladding fire. Prepare for panic and total evacuation of occupants. A floor above a fire can become unstable from sagging or buckle when steel beams fail.
  2. In a Type II battlespace, check the roof for fire extension before leaving the scene. If a combustible roof deck is seriously burning, withdraw Fire-
  3. In a Type III battlespace, open up those walls and ceilings and bring a thermal imaging camera to check for hot spots.
  4. In a Type IV battlespace, you have two chances to win this war--the first and second hose-lines. If they cannot extinguish the blaze, withdraw and protect exposures from at least an 80-foot distance of the radiation heat waves. Move the apparatus away from the building before radiation heat makes it impossible.
  5. In a Type V battlespace, the IC must must be ready to combat fire in the seventh side of the building--the exterior walls. Have an outside line ready for a two-front battle.

The game-changer

chapter image Fig. 26.6   Chronic fire spread matrix for each type of construction.

Firefighters’ radios must work properly and all reports of fire spreading in a building must be reported to Command. The IC's strategy is only as good as the information reported to the Command Post by Firefighters. The IC must encourage and train all Firefighters to continuously size up a fire and if they see something, they must say something, so Command can do something.


II. Chronic collapse

Any building can collapse any way, any time, at any fire. However, just as there are recurring fire spread patterns, there are also chronic repetitive collapse patterns. Each one of the five construction types has a structure design flaw in its construction method that is weakened and magnified during a fire and causes structure collapse. This section will examine specific design construction weaknesses, causing chronic or recurring collapse in each one of the five types of construction: Type I fire-resistive; Type II noncombustible; Type III ordinary; Type IV heavy timber; and Type V wood frame.

Type I fire-resistive construction recurring collapse

Floors are a recurring collapse danger in a fire-resistive building. Investigations of major fires in the U.S. show there is no record of a floor actually collapsing down to a floor below. However, investigations by the NFPA and UL of three major high-rise fires in the 20th century--One New York Plaza, Los Angeles First Interstate and Philadelphia One Meridian Plaza--revealed there was severe damage to composite steel and concrete floors. Steel floor beams were warped, bent and bowed downward, the fluted metal pan split at the seams and the concrete floor cracked and exhibited collapse warning signs.

chapter image Fig. 26.7   Concrete and metal composition floors of a Type I fire-resistive battlespace sag and crack when the underside is exposed to serious fire. This is a recurring collapse danger.

The floors after the fire was extinguished were found to be sagging so badly and cracked open, they had to be shored and braced before Firefighters could overhaul beneath them. During renovation, hundreds of steel floor support beams and fluted metal floor pans had to be replaced and new concrete poured over new steel floor framework. Investigations and photos revealed fluted metal under flooring sagged downward, causing concrete slabs above to crack, buckle and sometimes erupt upward, creating a wavy floor surface of the floor above a fire. When a floor area above a fire in a Type I building is cracked uneven or slanted downward, Firefighters cannot be ordered into the area to search. A floor may not collapse down to the floor below. However, when broken, slanted or wavy, the fire service must consider it a collapse danger.

After 9/11, NIST thoroughly investigated the collapse of building #7 in the World Trade Center complex. Floor collapse was the initial cause of this high-rise, Type I fire-resistive building. This building was not struck by a terrorist’s plane. Fire burned uncontrollably because Firefighters did not attempt to extinguish the blaze and sprinklers were not supplied with water because of broken water mains. NIST considered this the first Type I fire-resistive building to collapse due to fire destruction. After seven hours of uncontrolled burning, the first structure to fail was the floor. A floor beam on the 13th floor expanded from heat of the fire and pushed an interconnecting girder away from columns 79 and 44, causing floors to pancake down and trigger a (global) total collapse of the structure.

On January 19, 2017, a burning, 17-story, high-rise steel frame building (Plasco building) in Tehran, Iran, totally collapsed, killing a reported 20 Firefighters. One article said it was burning for three hours. Considering this fire and building number 7 of the World Trade Center, which burned for seven hours and collapsed, the U.S. fire service should consider limiting interior operations at high-rise fires to the hourly fire-resistance rating of the floors.

For example, if floors are rated for two hours of fire resistance (such as the WTC Tower floors), after two hours of interior firefighting, the Incident Commander (IC) should consider Firefighter withdrawal, using outside firefighting strategy. If floors are rated for three hours, the maximum interior firefighting time should be three hours.

At the One Meridian Plaza high-rise office building fire in Philadelphia, where three Firefighters were killed, interior operations continued for 11 hours. Too long!

At a typical, fire-resistive steel frame, high-rise building, columns can be rated for four hours of fire resistance, girders three hours and floors two hours. The fire service could use this fire-resistive time as a logical guideline for interior high-rise firefighting time. Hourly fire-resistive ratings for steel protection are obtained with a coating of spray-on, fire-retarding material. Recently, it has been discovered that when a sprayedon coating of fire-retarding material is used on steel located in a plenum ceiling space, the spray-on material can blow off the steel from the air movement of a HVAC system.

Today, there is still no standard documentation showing the relationship between the thickness of the spray-on material and hourly fire protection. Photos of the global collapse of the Iran 17-story high-rise showed large parallel chord steel truss construction in the rubble. The World Trade Center also had 60-foot-long, steel, parallel chord, bar-joist truss beams.

Spalling is another type of a Type I building floor collapse. There are two types of Type I fire-resistive construction--structure steel and reinforced concrete. A reinforced concrete building has a solid concrete floor without fluted steel pan and during a fire, heat can cause the underside of an exposed concrete floor to collapse downward. Spalling occurs when a section of masonry falls from the underside of a concrete floor.


Spalling concrete collapse in a Type I fire-resistive, reinforced concrete building is caused by the expansion of moisture in the concrete. All concrete has moisture in it and when heated by a fire, the moisture can expand into steam and explode a small chunk of concrete down on top of a Firefighter. Anytime flame and heat flow along the underside of a concrete floor, spalling can occur. Firefighters advancing a hose-line should direct the stream over the ceiling to cool and/or knock a loose concrete piece that may spall. “Over your head and all around” was the way old-timers described hose stream direction.

Type II noncombustible construction recurring collapse

A chronic collapse danger of Type II noncombustible construction is a floor or roof constructed of lightweight steel, open-bar joists. Every IC must know an unprotected, steel, open-bar joist can fail within five or 10 minutes of fire exposure (NFPA Handbook of Fire Protection, Sec. 19-50, Vol. II). “Forewarned is forearmed,” as the saying goes, so, too, at a serious fire in a noncombustible building, Firefighters should not operate on a roof supported by steel, open-bar joist construction.

Type II noncombustible construction is designed to house only low-hazard content, so ICs also must be aware of any occupancy change in a Type II building from low- to high-hazard content. If the content inside a Type II building changes and the hazard is increased from low- to medium- or high-hazard, automatic sprinklers must be installed, because unprotected lightweight steel used in a Type II structure can collapse quickly when exposed to fire.


Type III ordinary construction recurring collapse

chapter image Fig. 26.8   This global rooftop collapse in a Type II noncombustible/limited combustible battlespace was caused by heat of fire warping and bending lightweight steel, truss roof bar joists. Bar joist truss failure is a recurring collapse danger.

The recurring collapse of a burning Type III ordinary constructed building is a masonry wall. There is one brick wall of Type III building construction that is most unstable and often collapses during a fire--a parapet wall. A parapet wall is the portion of a wall that extends above a roof.

chapter image Fig. 26.9   Front parapet wall is a recurring danger of a Type III ordinary brick and joist battlespace. This wall collapsed suddenly after the fire was extinguished and hose was being taken up.

A one- to three-foot-high brick parapet wall on the front of a Type III building can extend around the perimeter of a building or be party walls separating buildings. This wall extending above the roof is exposed to the elements on three sides—top, inside and outside--and mortar can be eroded, causing it to lose adhesive qualities.

The most recurring parapet wall collapse is a decorative front wall on a one-story strip store. This wall can be balanced on a steel I-beam spanning large show windows. If, during a fire, the steel support beam bends, twists or warps, it can topple the parapet wall above.

When any wall appears unstable, there are three strategy options for an IC:

  1. Order a collapse danger zone established and have Firefighters operate away from the wall a distance of one, one and one-half or twice the height of the wall.
  2. Position an aerial ladder or platform to direct an aerial stream over the top of the wall. (Note: The aerial truck also must be parked outside the collapse danger zone.)
  3. While Firefighters are standing in front of an adjoining building, order them into a flanking position to direct hose streams from an angle into the building.

Type IV heavy timber construction recurring collapse

Of the important components of a structure--walls, floors, interior framing and roof--the interior framing is the heavy timber component that has a design weakness. The interior framing of large wood columns holding up massive wood girders, which support thick plank floors and roof, fails at the connections. The connections of columns, girders and beams are unrestrained connections that come apart during fire destruction. Once the interior framing is destroyed, floors collapse and cause wall collapse.

The builders brag about how the Type IV heavy timber, massive-size timbers provide fire resistance, how long it takes for timbers to burn and weaken and how this allows everyone to be evacuated from fire danger. This is true; it does take a long time for this timber structure to burn. However, Firefighters must remain on the scene during this burning. Firefighters still are operating hose-lines around the burning heavy timber structure as the building is burning and when it collapses.

chapter image Fig. 26.10   Wood framework floor connections and masonry walls are two recurring collapse dangers of the Type IV heavy timber battlespace.

During the height of a fire in a Type IV heavy timber building when the massive interior timbers are burning and generating tremendous waves of super-heated radiation to the surrounding streets, Firefighters must protect exposures and operate nearby when the timber framework comes apart and walls collapse. Collapse of the interior framing triggers masonry wall collapse. This may take hours or days. After the timbers are destroyed by fire, the walls have collapsed and some remain broken and freestanding, unsupported by timber framework, ICs must maintain the collapse danger zones around them even during the overhauling.

Type V wood-frame construction recurring collapse

There are many types of wood buildings, but one in particular presents a deadly collapse danger--the “triple-decker.” Three-story wood buildings collapse more frequently than one- or two-story wood buildings.


The design weakness of the Type V wood building is the structure walls. The walls of a three-story wood building present a chronic collapse danger. When a triple-decker collapses during a fire, the wood two- by four-inch bearing walls break apart, the lower part falls outward, the upper inward and, simultaneously, all the floors and roof pancake down. The design flaw is that two- by four-inch wood bearing walls support much larger and heavier two- by 10-inch floors and during a fire, the walls fail. One reason the walls break apart and collapse is unlike that of other buildings; there is no extra support of wood bearing walls on the lower floors. Even though wood floors at the ground floor support the load of the second and third floors, there is no increase in thickness or additional reinforcement. For example, construction of a masonry Type III building will have lower-floor bearing walls progressively thicker and as the wall increases in height and supports less load, they get thinner.

A warning sign of collapse of a three-story wood building is heavy fire fully involving the entire first floor, destroying the bearing walls. This fire must be considered a collapse danger as it burns the two- by four-inch bearing walls. Another warning sign of collapse can be flame coming out a window, spreading up a side bearing wall and destroying its support of the building. When a triple-decker appears in danger of collapse, the IC must establish a collapse danger zone around all sides of the structure because all four walls of this building can collapse simultaneously outward and the floors pancake--a global collapse.

Battle plans for chronic collapse of battlespaces:

  1. In a Type I battlespace, withdraw Firefighters when the floors sag and buckle from a fire below. This is a collapse warning sign. To protect against concrete ceiling spalling, direct a stream at a concrete ceiling before advancing. Before overhauling, shore up the sagging and cracked floors. Wear your helmet.
  2. In a Type II battlespace, conduct horizontal venting tactics. Stay off the roofs and floors if they are supported by open-web bar joists. Unprotected steel bar trusses can fail within five to 10 minutes of fire exposure.
  3. In a Type III battlespace, size up parapet walls and, if unstable, set up a collapse danger zone, flank the fire or use a master stream from above the walls.
  4. In a Type IV battlespace, if the two lines do not extinguish the fire, prepare for a conflagration. Withdraw Firefighters and don’t forget to move apparatus in the streets.
    chapter image Fig. 26.11   This global collapse of a three-story, wood-frame, Type V battlespace killed FDNY Lieutenant Robert Dolney, Engine 332, on March 5, 1980.
  5. In a Type V battlespace, the most dangerous building is a three-story structure, located on a corner or adjacent to an open lot, especially when there is heavy fire on the first floor. This structure can suffer a global collapse where all four sides can collapse simultaneously without warning.

The game-changers

chapter image Fig. 26.12   Chronic collapse matrix for each construction type.

Uncontrolled fire burning in a steel frame, fire-resistive, high-rise building for more than two hours is a game-changer. Another game-changer occurs when Firefighter radios are unable to work due to the steel or concrete of the building. Firefighters and Fire Officers must be able to transmit information about collapse warning signs to the IC. Firefighters and Fire Officers are the eyes and ears of the IC. An IC at a Command Post cannot see inside a burning building, cannot see roof conditions and cannot see the rear of a burning building. Only Firefighters and Officers at these locations discover collapse dangers. The IC can order a safety action strategy at a fire, but only after Fire Officers and Firefighters notify Command of the discovered collapse danger.

Battlespace Casualties:

Type I battlespace: NIOSH Firefighter fatality investigation F 99-FO1

Type II battlespace: NIOSH Firefighter fatality investigation F 2007-18

Type III battlespace: NIOSH Firefighter fatality investigation F 2002-44

Type IV battlespace: NIOSH Firefighter fatality investigation F 99 F47

Type V battlespace: NIOSH Firefighter fatality investigation F 2013-17



James E. Leonard, Chief of the New York City Fire Department, at the 50th anniversary of the 23rd Street fire, stated in Saint Patrick’s Cathedral on October 17, 2016: “There is no greater responsibility of Chief and Company Officers than to ensure the safety of all Firefighters.”

Glossary of Construction and Firefighting Terms

Meet Chief Dunn at his own kitchen table for his webinar series here.

Writing by Vincent Dunn


This building construction book lists a glossary of terminology about our battlespace building construction. This terminology is used during our structural firefighting battles and it is also a language used when communicating with the construction and engineering communities. Builders, construction engineers and structural Firefighters use a special terminology to describe parts of a building. Building terms and firefighting terms are used when communicating life and death orders at fires. Using specific terms to describe firefighting and construction at emergencies creates clear communications and quicker response. Good communications speeds up a lifesaving action.

Firefighting and building construction terms and definitions should be part of every course on building construction and be questions on exams to enhance Firefighters’ knowledge of our battlespace environment. Some Firefighters are vaguely aware of a building construction term without having precise knowledge. The following 100 plus building and firefighting definitions are presented in this book to facilitate accurate communications in our firefighting battles. This chapter should be read first to better understand these terms as they are used throughout the text.

  1. Access Stair: An unprotected open stairway between floors in high-rise office buildings. There can be up to four floors connected by access stairs, sometimes called a convenience stair. This stair allows occupants to go from floor to floor without going out to the lobby to use an elevator. This stair also allows fire and smoke to spread from floor to floor.
  2. Active Fire Protection: Firefighters with hose streams, automatic sprinklers and smoke detectors are considered active fire protection. Passive fire protection includes walls, floors and ceilings of building construction that resists fire spread.
  3. Arch Roof: An arch roof differs from a truss roof. An arch roof beam is a single, continuous, curved roof member of wood, concrete or steel, shaped like a rainbow. There are no web members or bottom chord in an arch.
  4. Attic: A space or room just below the roof. An attic is similar to a cockloft or common roof space.  
  5. Balloon Construction: One of the four basic methods of constructing wood-frame residential buildings (braced-frame and platform and lightweight truss are the other types). Balloon frame buildings’ exterior walls have studs extending continuously from the structure’s foundation sill to the top plate near the attic. The concealed space between these studs can spread fire, smoke and heat from the cellar area or the intermediate floors to the attic space. If a non-bearing wall collapses during a fire, the continuous studs will cause the wall to fall straight outward, in one section, at a 90-degree angle. If a bearing wall of a balloon-constructed building fails, it can cause a second collapse of the floors it supports.
  6. Battlespace: A battlespace is the total fire environment, the inside and outside of a burning building. A battlespace is not just the room and fire; it includes much more. It is the stair enclosure we use to get to the fire, room configurations, rooftop hazards, structure framing, metal fire escapes, ceiling spaces, voids behind walls and floors and roof construction. The term, battlespace, is not the same as battleground or fireground; it is the total firefighting environment that must be understood to successfully combat fire, protect Firefighters and complete the mission of saving lives and property.
  7. Beams: A beam is a horizontal structural member, subject to compression, tension and shear, supported by one of three methods:
    1. Cantilever Support Beam: A beam supported or anchored at only one end, which is considered a collapse hazard during fire exposure. Examples of cantilever structures are an ornamental stone cornice, a marquee, a canopy, a fire escape and an advertising sign attached perpendicularly to a wall. Of the types of beam supports, it has the least amount of structural stability during a fire.
    2. Continuous Support Beam: A beam supported at both ends and at the center. During a fire, it has the greatest structural stability of the three types of beam supports.
    3. Simple Supported Beam: A beam supported at both ends. If the deflection at the center of such a beam becomes excessive, a collapse may occur. A simple supported beam is more stable under fire conditions than a cantilever beam, but less stable than a continuous supported beam.
  8. Braced-frame Construction: One of four basic methods of constructing wood-frame residential buildings (balloon, platform and lightweight truss are the other methods). Braced-frame construction sometimes is called post and girt construction. Vertical timbers called posts reinforce each of the four corners of the structure and horizontal timbers called girts reinforce each floor level. Posts and girts are connected by fastenings called mortise and tenon joints. During a fire, a braced-frame building wall often fails in an inward/outward collapse. The wall breaks apart with the top part collapsing inward on top of the pancaked floors and the bottom part collapsing outward onto the street.
  9. Bulkhead: A structure built over or enclosing a stairway, elevator, dumbwaiter shaft or other building facility on the roof of a building.  
  10. Buttress: A wall reinforcement or brace built on the outside of a structure, sometimes called a “wall column.” On a masonry wall, a buttress is a column of bricks built into the wall. When separated from the wall of a buttress on an exterior wall, it can indicate the point where roof trusses or girders are supported by a bearing wall. A buttress constructed on the inside of a wall is called a pilaster.
  11. Canopy: A shed-like cantilever structure over a building entrance or truck loading platform to protect people from the elements.
  12. Cantilever: A cantilever is a beam supported at one end, unlike a simple beam, which is supported at both ends.
  13. Cast-iron Column: A column of iron and carbon that has been cast in a column-shaped mold. Iron that has been melted is poured into a mold and allowed to cool. If the mold is defective, the cast-iron column is defective. Cast iron has weak tensile strength and will fracture before it bends or distorts.
  14. Coaming: A raised frame around a floor or roof opening to keep water from running into the opening.
  15. Cockloft: A space between the roof and the top-floor ceiling that extends over an entire top floor of a building.
  16. Column: A vertical structural member subject to compressive forces. The structural framework of a building consists of vertical and horizontal elements. Columns and bearing walls are parts of the vertical framework; girders and beams are parts of the horizontal framework. Bearing walls, columns and girders can be classified as primary structural members. They support other parts of a structure and their collapse can trigger a secondary collapse of other structural members. Other primary structural members are ridgepoles, hip rafters, headers and trimmer floor beams.
  17. Common Roof Space: A common roof space is a cockloft space that is connected to adjoining structures’ cocklofts. A common roof space may extend over all the row buildings of a block.
  18. Compactor: A device for crushing garbage and trash into a small space prior to removal from the premises.
  19. Compression: It is the application of an inward or pushing force to different points on a beam. It is the opposite of a tension force--the application of outward or pulling force.
  20. Convenience Stair: An unprotected open stairway between floors. Sometimes called an access stair.
  21. Coping Stone: The top masonry tile or stone of a parapet wall, designed to carry off rainwater. Sometimes called a “capstone,” it weighs between five and 50 pounds. A coping stone can be dislodged and fall from a parapet under the impact of a high-pressure master stream or when struck by a retracting aerial ladder or platform. Firefighters have been killed or injured by falling coping stones.  
  22. Corbel Shelf: Corbel brick or corbel stone projects out from the surface of a wall, similar to a cantilever. It can make a wall unstable. It can be a decorative ornament on the top of a parapet front wall or it can be used on the inside of a brick wall as a support for a roof beam end. A corbel used on the inside of a masonry wall to support a beam is called a “corbel ledge” or “corbel shelf.” Under the weight of a Firefighter, a roof beam end that is resting on a corbel ledge can rotate off its support if the center of the beam has been burned away.
  23. Cornice: A horizontal architectural element that projects out from the front wall of a building. It forms a crowning feature at the top of a building. A cornice may be wood or sheet metal with a wood framework. Fire can spread from one building to another in a wood cornice or the wood framing inside a sheet metal cornice. A stone cornice on a parapet wall is a collapse danger. (See Eaves and Soffit.)
  24. Cross-laminated Timber (clt): Cross-laminated timber is manufactured wood consisting of three or four layers of smaller wood, laid in a crossing pattern and glued together, forming large, timber columns or beams. This cross-laminated timber was approved by the International Building Code in 2015 and is being used to build wood timber high-rise construction. Builders claim the benefits of CLT are that it does not catch fire easily and once it is ignited, it wants to put itself out; it provides fire resistance; and maintains significant structure capacity for extended duration when exposed to fire. There are plans to build high-rise structures using CLT. The fire service does not agree with these claims and discourages construction using CLT wood timber for high-rise structures.
  25. Deck: A horizontal surface covering supported by a floor or roof beam. When an arsonist spills an accelerant on a floor or roof to start a fire, the deck area inside the spill is charred and weakened. Firefighters searching or advancing hose-lines in such a building often plunge through collapsing decks. It is difficult for a Firefighter to remove a leg or foot from a hole in a plywood deck; splintered edges of the hole act as a trap.
  26. Deflection: A bend, twist or curve of a structural element under a load. All structures deflect slightly when supporting a load, but a structural element is designed to withstand a load without showing signs of deflection. When a Firefighter notices the deflection of a column, beam or wall, this is a collapse warning sign and should be reported to the Officer in command.
  27. Dumbwaiter Shaft: A device inside a shaft for collecting garbage from apartments by means of a wooden car, which is raised and lowered in a vertical shaft by means of a rope and pulley. In most buildings with these dumbwaiters, they no longer are used and are sealed up. However, they can spread fire from the cellar up into the cockloft.  
  28. Eaves: The lower edge of a roof that overhangs a wall. The sloping lower edges of a gable roof that overhang walls are called eaves. Flame spreading up a wall can burn through the underside of the eaves. (See Cornice and Soffit.)
  29. Exterior Insulation Finish System (eifs): Exterior insulation finish system used as part exterior wall cladding on low- or high-rise buildings has become a major fire service concern. This exterior renovation creates another avenue of exterior fire spread in high- and low-rise buildings. The outside walls of all types of construction, including Type I fire-resistive, now must be considered highly combustible. Exterior fire then can spread up the exterior of any building and then inside rooms through windows. Sometimes, the exterior cladding fuel problem is the flammable insulation installed between the old exterior wall and the new metal cladding. Other times, it is the flammable glue that fastens the exterior wall.
  30. Facade: The front or face of a building. A façade may include four collapse dangers: a marquee, a cornice, a canopy and a parapet wall. The portion of the facade wall that extends above the roof level is called a “parapet wall.” The facade parapet is often a freestanding, decorative wall that frequently collapses during a fire.
  31. Fire Curtain: A fire curtain is found in a bowstring truss roof building. It is a one-hour plasterboard covering over the web member of a truss, intended to stop fire from spreading through web members of a timber truss. A fire curtain is a fire cutoff in a truss roof concave space or in a truss roof attic space.
  32. Fire-cut Beam: A gravity-support beam end designed to release itself from the masonry wall during a collapse. The end of the wood beam, where it rests within the cavity of a masonry wall, is cut at an angle. This self-releasing beam is designed to save the expensive masonry wall during a fire and resulting collapse. An unintended indirect advantage of the fire-cut beam end is the safety of Firefighters operating outside the building near the enclosing walls; the floor collapse will not topple the bearing walls outward on top of them. A disadvantage of the fire-cut beam to Firefighters operating inside a burning building is early floor collapse.
  33. Fire Escape: An emergency means of egress consisting of metal or a wood balcony on the outside of a building, connected by ladders to each floor, roof and ground level or used as a horizontal exit to an adjoining building.
  34. Fire Load: The measure of maximum heat release when all combustible material in a given fire area is burned. The content and structure of a building contribute to fire load; structural collapse during a fire is directly proportional to the fire load. The greater the fire load, the greater the possibility of structural collapse during a fire.
  35. Fire-resistance Rating: A relative rating to indicate in hours how long a wall, floor, ceiling, beam or column will sustain fire-resistance performance.  
  36. Fluted Metal Steel Deck: A wavy piece of sheet steel deck used to support concrete floor. Sometimes called a corrugated metal floor deck.
  37. Frame Tube Construction: The World Trade Center towers were frame tube construction. The building structure had hollow tubular bearing walls. Frame tube exterior hollow bearing walls varied from four inches in thickness near the bottom, to only ¼-inch thickness near the top and contributed to the early, rapid collapse during 9/11.
  38. Game-changer: A game-changer is discovery of significant fire spread or construction feature that should be reported to the Incident Commander (IC). A game-changer can change or alter an IC’s strategy.
  39. Girder: A horizontal structural element that supports a floor or roof beam. It can be considered a primary structural member, along with a column and a bearing wall. The collapse of a primary structural member can cause the collapse of another structural member.
  40. Global Collapse: A total collapse of a building. The World Trade Center towers and Building #7 were examples of a global collapse. (See Progressive Collapse.)
  41. Gravity Load: A combination of dead load and live load.
  42. Gusset Plate: (Sheet metal surface fastener) A structure fastener in the form of a flat metal plate used to connect structural members. A steel plate with steel bolts and nuts is an example of a gusset plate connection. Another inferior type of gusset plate, called a “sheet metal surface fastener,” is used on lightweight wood trusses. It is a quarter-inch-thick piece of sheet metal with many small, triangular holes, punched through it by a stamping machine. The V-shaped points caused by the hole punches substitute for the steel bolts and nuts of the old gusset plates. These points are only one-half-inch long and act as nails. The nailing points penetrate the wood trusses only a fraction of an inch. During a fire, the sheet metal surface fasteners quickly fall off the structure; heat warps and bends the sheet metal connectors and surface charring weakens the nailing surface. During shipping and unloading at the construction site, these connectors may be knocked loose from the wood trusses. From a fire protection point of view, a sheet metal surface fastener is an inferior, dangerous connector.
  43. Header Beam: A support used to reinforce an opening in the floor of a wood-frame, ordinary or heavy timber building. A header beam (sometimes doubled for increased strength) is placed perpendicularly between two trimmer beams and supports the shorter, cutoff beams called “tail beams.” An opening in the floor is encircled by the header and trimmer beams. If a Firefighter cuts through or pulls down a header beam, the tail beams and floor deck subsequently can collapse.
    chapter image Fig. 1 Glossary   Tail and trimmer beams of a floor opening.
  44. Hierarchy Of Building Elements: Horizontal and vertical structural elements of a building arranged in a collapse hierarchy. The collapse of certain structural elements is more dangerous than the collapse of other structural elements, depending upon where they fit in the hierarchy.
  45. Structural Element Seriousness of Collapse
    Deck Less
    Bearing Wall More
    chapter image
  46. I-beam: A wood or steel I-beam consists of a center called a web section and top and bottom flanges. Wood I-beams have a web section of glue and wood shavings connecting the top and bottom flanges made of wood sections measuring two by two inches.  
  47. Intersititial Space: A concealed space between floors used to contain large mechanical and electrical equipment. The space can be up to eight feet high and contain a walkway for access for maintenance, repairs and renovations. Plenums sometimes are called interstitial space when they contain electric and HVAC utilities.
  48. Joist: A piece of lumber used as a floor or roof beam. The terms--joist, beam and rafter--are used interchangeably. A joist supports a roof or floor deck and often is supported by a girder.
  49. Kip: One kip equals a thousand pounds. When measurements expressed in pounds become large and unwieldy, kips are used to simplify the figures. The term, kips, most often is used when stating the strength of steel; K.S.I. is the abbreviation for kips per square inch.
  50. Knee Wall: A short wall, usually less than three feet, used to support rafters in a sloping peaked roof. Fire and smoke can build up in the void behind a knee wall in an attic and when opened by Firefighters to check for fire, quickly can fill up an attic and trap Firefighters.
  51. Laminated Beam: A glued or layered composition beam. Lamination wood chips are used in lightweight wood I-beams and layered; bent wood is used in bowstring timber truss top chords.
  52. Lightweight Truss Wood Construction: One of the four types of wood-frame construction. Balloon, braced-frame and platform are the other three. A lightweight wood truss building has truss-constructed floors and roof. The truss webs and chords are attached by sheet metal surface fasteners, a defective connection. With this construction, floors and the roof can collapse within five to 10 minutes of fire exposure. This construction sometimes is called a house of sticks. Nothing in the construction is larger than two- by four-inch wood pieces. From a fire protection point of view, it is inferior to the other three types of wood construction.
  53. Lintel: The steel beam that supports a parapet wall on storefront walls with large, glass show windows is called a lintel beam. A horizontal piece of timber, stone or steel is placed over an opening in a wall. The lintel is a load-bearing structural element that supports and redistributes the load above the opening. The failure of a lintel during a fire can cause the collapse of the wall above the opening. Flame and heat issuing from a window of a burning building weaken the lintel spanning the top of the window opening.  
  54. Loads: Forces acting upon a structure. The following are loads acting on a building:
    1. Axial Load: One of the three ways a load can be imposed upon a supporting structural element (eccentric and torsional loads are the other two methods). An axial load passes through the center of a structure and is the most efficient manner by which a load can be transmitted through a structural support, such as a column or a bearing wall. A structural element can withstand its greatest load—and is less likely to collapse—when the load imposed is axial. Loads designed to be transmitted as axial loads become eccentric (offcentered) or torsional (twisting) loads. Structural collapse can occur during a fire when a dead load transmitted through a column or bearing wall changes from an axial load to an eccentric or torsional load.
    2. Concentrated Load: A load applied at one point or within a limited area of a structure. The concentration of heavy, cast-iron fixtures inside a small bathroom can be considered a concentrated load. When weakened by fire, the bathroom floor can collapse under the weight of the heavy bathroom fixtures confined in the small floor area. A load distributed over a large area creates less strain on a supporting structure during a fire than does a load in a small area.
    3. Dead Load: One of the five major loads that must be considered in the design of a building (live, wind, impact and seismic loads are the others). A dead load is a static or fixed load created by the structure itself and all permanent equipment within. Walls, floors, columns and girders arc part of the structural dead load. Airconditioning machinery, fire escapes, suspended ceilings, roof water-storage tanks and advertising signs are part of the equipment dead load. Firefighters have been killed by the collapse of dead loads.
    4. Eccentric Load: A load transmitted off-center or unevenly through a structural member. During a fire, a load designed to be transmitted axially slowly can become an eccentric load when steel columns or girders expand, timber surfaces char or concrete spalls and exposes reinforcement steel. When load transmission slowly changes during a fire from axial to eccentric, the strength of the structure is seriously diminished. When floors collapse inside a burning brick-and-joist building, the load on the bearing walls shifts violently from a vertical axial load to a lateral eccentric load. This shift often causes the walls to collapse.
      chapter image Fig. 2 Glossary   Axial, eccentric and torsional loads.
    5. Impact Load: A load applied to a structure suddenly, such as a shock wave or a vibrating load. It can cause a structure to collapse more readily than a slow, steady, evenly applied load. An explosion, a master stream directed at a structure in a whipping or pulsating manner or heavy ground ladder placed forcefully against a structure are examples of impact loads that can cause structure collapse.  
    6. Lateral Load: Any type of load applied to an upright structure from a direction parallel to the ground. Examples of lateral loads are wind loads, tips of ladders placed against structures, horizontal explosion shock waves and hose streams. Most upright structures are not designed to withstand lateral loads. A structure capable of withstanding great vertical loads may collapse under slight lateral loads.
    7. Live Load: A transient or movable load, such as a building’s content, the occupants, the weight of Firefighters, the weight of fire equipment and the water discharge from hose streams.
    8. Static Load: A load that remains constant, applied slowly. A structure may support a greater amount of static load than impact load. An example of a static load is the content of a floor used for storage. A Firefighter who slowly and softly applies his weight along a roof deck above a fire or on a fire escape step is demonstrating the principle of static loading.
    9. Torsional Load: A load that creates a twisting stress on a structural member. When a large steel girder collapses at one end, the other end experiences a torsional or twisting stress.
    10. Wind Load: A lateral load imposed on a structure by wind. A wind load may tear a roof off a structure or collapse a freestanding parapet wall or chimney.
    chapter image Fig. 3 Glossary   Compression, tension and shear stresses.
  55. Load Stress: An internal stress created by a load in a structural element, including compression stress, tension stress and shear stress. A collapse can occur when a stress created by a load exceeds the load-carrying capability of the structural element. An example of collapse by compression stress is the failure of a steel column weakened by the heat of combustion; one of collapse by tension stress is the failure of fire-weakened steel or wood hanger straps holding up a suspended ceiling; one of collapse by shear stress is the collapse of a brick veneer wall breaking away from the cement bonding and falling in curtain-fall collapse.
  56. Marquee: A roof-like projection used as an advertising sign over the entrance of a theater, hotel or department store. A hollow constructed marquee is called a swimming pool hanging on the front wall of a building. It can fill up with water or snow and become a collapse danger.  
  57. Mortise: A structural connection often used in braced wood-frame construction, it is a hole cut into a timber that receives a tenon. The mortise opening reduces the thickness of the timber and reduces the load-carrying capability of the timber at this point. When the timber-braced framework fails during a fire, it often breaks apart at the mortise and tenon connection, which has become weakened by flames and decomposition.
  58. Noncombustible Construction: Material that will not add fuel to a fire or spread fire. This term is not the same as fire resistance. Noncombustible construction will not resist fire. Fire-resistive construction will resist fire.
  59. Open-web Steel Bar Joists: A lightweight steel truss used as a floor or roof beam. It is made from a steel bar, bent at 90-degree angles, welded between angle irons at the top and bottom bar bends. This open-web bar joist is used for floor and roof beams in noncombustible buildings. An unprotected, open-web, steel bar joist can collapse after five to 10 minutes of fire exposure.
  60. Passive Fire Protection: Fire protection created by walls, floors, partitions and ceilings. Passive fire protection claims to restrict fire spread by construction only, without assistance from active fire protection, such as sprinklers, Firefighters or smoke detectors. Recent high-rise fires have debunked the term, passive fire resistance.
  61. Pilaster: A masonry column bonded to and built as an integral part of the inside of a masonry wall. Sometimes called a “wall column,” a pilaster can carry the load of a girder or timber or it can be designed to provide lateral support to a wall. (See Buttress.)
  62. Platform Wood-frame Construction: One of the four methods of wood-frame residential building construction (the others are balloon, braced-frame and lightweight truss). A building of this construction has one complete level of two- by four-inch wood enclosing walls raised and nailed together; the floor beams and deck for the next level are constructed on top of these walls. The next level of two- by four-inch wood enclosing walls then is constructed on top of the first completed level. From a fire protection standpoint, platform construction is superior to balloon and braced-frame construction because there are no concealed wall voids extending for more than one floor level. Platform construction was a superior type of wood construction; however, it now incorporates lightweight wood truss and wood I-beams for floors and roofs, which make it an inferior type of wood construction. From a fire protection and collapse point of view, platform construction using lightweight wood construction and wood I-beams for floors and roofs is dangerous for Firefighters.
  63. Plenum: A plenum is an undivided, suspended ceiling space, used as an air holding space for a heating and venting system in a fire-resistive building. It is used to store, supply or exhaust air recirculating in an HVAC system in Type I and II construction. This ceiling space can contain combustible computer and electric cable insulation made of plastic or rubber, which emits large amounts of smoke when burning.  
  64. Primary Structural Member: A structure that supports another structural member in the same building, such as a bearing wall, column or girder. The collapse of a primary structural member often will cause the collapse of the structural member it supports.
  65. Progressive Collapse: This is when the initial structural failure spreads from the structural element to other structural elements, resulting in the collapse of an entire structure or a disproportionately large part of it.
  66. Purlin: A timber placed horizontally to support the common rafters of a roof.
  67. Q-deck Flooring: A lightweight floor system of corrugated steel forms with two inches of concrete top surface. This lightweight floor system was used in the World Trade Center buildings that collapsed on 9/11. (See Fluted Metal Steel Deck.)
  68. Rain Roof: A roof deck built over an old roof deck that is sagging to keep rain water from pooling up and is slanted to let the roof drain. This is different from a raised roof.
  69. Raised Roof: A roof that is raised above the roof beams and supported by 2 by 4s. The extent to which it is raised varies to provide proper drainage on the roof. The result is a large open cockloft where fire can spread easily.
  70. Restrained Beam End: A welded, nailed, bolted or cemented end of a floor or roof beam. It is one of two methods of supporting a beam end; the other is an unrestrained beam. During a fire, a restrained beam end will not collapse as readily as an unrestrained beam end. A wood beam cemented into a cavity of a brick wall is an example of a restrained beam end.
  71. Returns: The interior surface of a scuttle or skylight opening, forming the walls between the roof and the top-floor ceiling.
  72. Ridge Pole: (Ridge rafter or ridge beam) A horizontal timber that frames the highest point of a peak roof. Roof rafters are fastened to the ridgepole at the top and bearing wall at the bottom.
  73. Roof: The sheltering structure of a building that protects the interior spaces from natural elements. It is designed to support dead loads--such as the roof deck, roof shingles, suspended ceilings and suspended lights--and live loads, such as snow. A roof is not designed to support the weight of Firefighters and their equipment.  
  74. Safety Factor: The quotient of the load that will cause a structure to collapse, divided by the load a structure is designed to support. If a floor beam is designed to support a load of 100 pounds per square foot and the floor has been tested and found to collapse at 200 pounds per square foot, the safety factor of the floor is two. Most structural elements are designed with a safety factor of two or more. A safety factor provides the structural engineer and the designer with a cushion or margin for error in case there is an unknown factor in the load-bearing capability of a structural element. Years ago, little was known about failure points and accurate strength testing of structural materials; to compensate, built-in safety factors were large. Today, with improved testing techniques and computers to calculate precise collapse points, the built-in safety factor is being reduced and, in some instances, eliminated. Lightweight building construction is one result of the reduction in safety factors.
  75. Shaft: A space between buildings or between rooms within a building, provided for the purpose of admitting air and light to rooms.
  76. Shear: A stress causing a structure to collapse when contacting parts or layers of the structure slide past one another. A brick veneer wall breaking away from the cement bonding to the back wall and collapsing to the sidewalk is a structural failure caused by shearing. Also, a steel bolt connecting a fire escape step to a stringer will shear apart when it has rusted over the years and is forced to respond suddenly to the impact of a Firefighter's foot.
  77. Sleepers: Wood sleepers are strips of wood embedded in the top of the concrete used to nail floorboards.
  78. Soffit: The underside of an eave, cornice, arch or deck. Flame blowing out a top-floor window can burn through a soffit of an eave or cornice into an attic or cockloft.
  79. Spandrel Wall: That portion of an exterior wall between the top of one window opening and the bottom of another. If a brick arch or a wood, concrete or steel lintel spanning the top of a window supporting a spandrel wall is weakened by fire, blasted away by a high-pressure master stream or removed during overhauling, the spandrel wall can collapse.
  80. Sprayed-on, Fire-Resistive Material: (SFRM) Sprayed-on, fire-retarding material must cover the steel entirely, must be of proper thickness and/or density and must adhere to the steel and not flake off when exposed to air movement in a HVAC plenum area. SFRM: Initials used for “sprayed-on, fire-resistive material,” referred to as insulation or fluffy, spray-on fire-retarding, used to protect steel from the heat of fire.
  81. Stress: A force exerted upon a structural member that strains or deforms its shape. The terms, stress and load, often are used interchangeably. The three common types of stress are compression, shear and tension. Compression is a force pressing or squeezing a structure together. A steel column is subject to compression, but when heated by a fire, it loses its compressive strength. When the heated steel column buckles and distorts, it collapses under the forces of compression from the load it is supporting. Some materials are strong in compressive strength and weak in tensile strength. Steel is strong in compressive and tensile strength; concrete is strong in compressive strength and weak in tensile strength; rope is strong in tensile strength and has no compressive strength.  
  82. Suspended Ceiling: A ceiling built several inches or feet below the supporting roof or floor beams above; sometimes called a “hanging” or “dropped” ceiling. The concealed space above the ceiling sometimes is called a “cockloft.” The suspended ceiling is attached to beams above by means of vertical wood, wire or steel straps. The ceiling is held up by the collective strength of all the hanger straps. If several ceiling hanger straps are destroyed by fire or removed during overhauling, the remaining straps may not be able to support the ceiling. A progressive total collapse of an entire stucco or cement ceiling can occur when the support of several hanger straps is eliminated.
  83. Tenon: A projecting, reduced portion of a timber designed to be inserted into the mortise hole of another timber. The tenon used with a mortise is a connection employed in braced wood-frame residential construction. Because of its reduced size, the tenon connection is the weakest portion of the timber; it can be destroyed by fire and decomposed by exposure to moisture.
  84. Tension: Stress placed on a structural member by the pull of forces, causing extension. Tension is the opposite of compression. For example, the hanger straps supporting a suspended ceiling are under the stress of tension.
  85. Terrazzo: A polished floor covering made of small marble chips, set in several inches of cement. A terrazzo floor is a collapse hazard; it adds weight to floor beams, conceals the heat of a serious fire below and, because it is water-tight, allows water to accumulate and build up to dangerous proportions. In New York City in 1966, a fire burning in a cellar below a terrazzo floor burned away the floor beams, although little heat and smoke penetrated the floor itself. The floor suddenly collapsed, killing 12 Firefighters.
  86. Timber: Wood larger than two by four inches.
  87. Topography: The detailing, charting, drawing or floor layout of a fire area.
  88. Trimmer Beam: A wood beam constructed around the perimeter of a floor or wall opening. In a floor opening, a trimmer beam supports the header beam which, in turn, supports the tail beams. When a floor area is designed to create an opening for a stairway, the edge of the opening is surrounded by header and trimmer beams. Header and trimmer beams are primary structural members that, if they fail, will cause the collapse of other sections of the floor.  
  89. Truss: A braced arrangement of steel or wood framework made with triangular connecting members. The truss presents several dangers to Firefighters. It suffers early collapse during a fire because its exposed surface area is greater than the exposed surface area of a solid beam spanning the same distance. Also, there are a greater number of connections in a truss and, if any one fails during a fire, it can trigger the entire truss to collapse. Truss roof beams are spaced farther apart than solid beams, creating larger areas of unsupported roof deck. When the truss collapses, large areas of roof deck collapse. The failure of one timber truss of a number of trusses spaced 20 feet apart, supporting a 100- by 100-foot roof, can collapse 4,000 square feet of roof deck. A bowstring or peak timber truss roof creates a concave space on the underside of the roof, where great quantities of heat and flame can accumulate. A Firefighter walking upright in a fire area where heat and flame have accumulated high above his head can miscalculate the amount of fire inside an occupancy.
  90. Unrestrained Beam End: A beam end resting on a support, held in place only by gravity. During a fire, an unrestrained beam end will collapse more readily than a restrained or fixed beam end. An example of an unrestrained beam end is a fire-cut beam or a beam resting on a corbel ledge or girder.
  91. Wall, Area Wall: A freestanding masonry wall surrounding or partly surrounding an area (for example, a masonry fence).
  92. Wall, Bearing Wall: An interior or exterior wall that supports a load in addition to its own weight. Part of the skeletal framework of a structure that most often supports the floors and roof of a building.
  93. Wall, Curtain Wall: An exterior wall of Type I and Type II construction of aluminum, stainless steel, glass, masonry or plastic. It extends over the entire face of the building and is attached by bolts to the outer edge of the floor slabs. There usually is a small space between the outer edge of the floor slab and the inside of the curtain wall through which flames and smoke can spread to the floors above.
  94. Wall, Demising Wall: A partition wall that extends from floor slab to floor slab above.
  95. Wall, Fire Wall: A non-bearing, self-supporting wall designed to prevent the passage of fire from one side to another. Any door or window built into a fire wall must be equipped with an opening protective closure designed to prevent fire spread. The fire wall must be independent of the roof structures on either side and be designed to withstand complete collapse of a structure on either side. Party walls with parapets extending above a roof are not true fire walls. Often featuring penetrating openings that are not equipped with fire-rated doors or windows, party walls collapse if the interconnected wall or roof fails during a fire.
  96. Wall, Freestanding Wall: A wall exposed to the elements on both sides and the top, such as a parapet wall, a property-enclosing wall, an area wall and a newly constructed exterior wall left standing without roof beams or floors. Of the three types of walls—freestanding, non-bearing and bearing— the freestanding wall is the most unstable and likely to collapse at a fire because it has fewer supporting connections to the structure.
  97. Wall, Knee Wall: A short wall in an attic, typically less than three feet in height, used to support the rafters in peak roof construction.  
  98. Wall, Parapet Wall: The continuation of a party wall, an exterior wall or a fire wall above the roof line. Parapet walls are considered freestanding walls and are less stable during fire conditions than non-bearing or bearing walls. The parapet of an ornamental stone front wall in a one-story commercial building, with large display windows beneath it, is a collapse-prone structure during a fire. One-story shopping center structures with large show windows often have parapet walls resting on steel lintels. The steel lintel beam spans the large show windows and supports the wall above. A parapet wall supported by such a lintel can become unstable and collapse if the steel shifts or warps as a result of expansion caused by the heat of a fire. The impact of a master stream also can collapse a freestanding wall.
  99. Wall, Party Wall: A bearing wall that supports floors and roofs of two buildings. The collapse or demolition of one of the buildings served by a party wall may affect the stability of the adjoining structure. Although it does act as a fire barrier, a party wall is not designed to be a fire wall; fire can spread through a party wall that has wood beams embedded in brick cavities.
  100. Wall, Spandrel Wall: That portion of an exterior wall between the top of one window opening and the bottom of another. If a brick arch or a wood, concrete or steel lintel spanning the top of a window supporting a spandrel wall is weakened by fire, blasted away by a high-pressure master stream or removed during overhauling, the spandrel wall can collapse.
  101. Wall, Veneer Wall: A finished or facing brick or stone wall used on the outside of a building. A veneer wall is fastened to a backing wall by sheet metal ties or cement. The sheet metal ties or cement bindings sometimes are omitted, defective or improperly installed, creating an unstable veneer wall. A veneer wall will collapse in a curtain-fall fashion during a fire.
  102. X Box: The marking of a vacant building with a painted, 18-inch square box with an X inside it. An X box indicates the building has numerous structure hazards and defensive, exterior firefighting should be considered.
  103. Yard Hydrant System: A yard hydrant system is a privately owned water system of mains, hydrant hose and stationary nozzles built on private property.
  104. Zone Of Collapse Danger: Zone of danger is a distance equal to one, one and one-half or two times the height of an unstable wall. The collapse zone distance is determined by the Incident Commander.