THE DANGEROUS “FIVE CLASSES OF BUILDINGS”
BY FRANCIS L. BRANNIGAN, SFPE (FELLOW)
I can`t say how many fire-fighters have died because they were operating below hidden fire overhead, but there are many. If you hear crackling from a floor or ceiling above you, pulling the ceiling may provide the fire with the oxygen it needs to blow and bring down the structure.
I have recently learned of what must be the most important innovation in fire technology in decades. Captain Scott Cook of the Granbury (TX) Fire Department led his crew into a working fire in a commercial building. He used his thermal imaging camera to look for victims not only at the floor but also at the overhead area. The imager indicated that fire was raging overhead. He withdrew his crews just moments before the structure collapsed.
For years, I have used the figure of speech “undress the building” to mean that you must picture in your mind the building`s hidden structure based on your study and knowledge of the building. Now, the admonition can be literal. If fire chiefs will get excited about saving lives and will obtain the funds to purchase thermal imaging cameras, firefighters` lives will be saved. I would appreciate hearing of cases in which serious fire was seen on the imager and the action that was taken as a result.
Firefighters are learning to rattle off the “five classes of buildings” without any qualification. I urge every instructor who uses the five classes in any material to present the following potentially life-saving information.
These broad classifications are favorites of those who write examination questions. Originally developed as a rough cut for insurance rating, they are dangerously incomplete for firefighters and may lead to deadly assumptions about a particular building. Many buildings include several types of construction, some or all of which may not conform in dangerous details to the five standard categories. Numbers in parentheses refer to referenced page numbers in the third edition of Building Construction for the Fire Service. Know your buildings–the buildings in which you must fight fires.
Fire-Resistive Buildings
Fire-resistive rated elements may vary greatly in quality. For instance, removing a single ceiling tile from a rated fire-resistive floor-ceiling assembly of bar joists and suspended ceiling tiles can reduce the rating to a noncombustible status and cause the assembly to lose all fire resistance value. (294)
Concrete buildings must have metal expansion joints in floors and possibly walls. In the Chicago, Illinois, McCormack Place fire and the New York City Parcel Post Annex fire, such joints extended fire. See “Fire Resistance Ratings” below for the severe limitations of hourly ratings. It cannot be assumed that rated fire resistive structures will prevent extension of fire or migration of smoke and toxic gases.
“Noncombustible Buildings”
“Noncombustible buildings” may have many combustible features, such as roofs, balconies, overhangs, and metal deck roofs (302-309) Noncombustibility does not indicate any designed resistance to collapse. (282) “Protected noncombustible” structures have certain columns and beams protected (insulated) to keep the sprinkler system supports from collapsing until the sprinklers can control the fire. The term “protected” construction (based on the building code) is related to the protection of the structural members, not the presence of an automatic sprinkler system.
Ordinary Construction
Ordinary construction buildings have masonry exterior (brick, concrete block, stone, or cast-in-place concrete) bearing walls that may help control extension of fire to other buildings. For this reason, many building codes define a congested area (sometimes called the “fire limits”), in which, as a minimum, masonry exterior walls are required on all buildings. The interior is combustible wood construction.
Because brick is a popular finish and the cost of repainting wood is high, buildings that appear to be solid masonry may be various combinations of solid masonry and veneered masonry in which one thickness of masonry is attached to a wooden (usually, but it can be concrete or steel) wall. If a wall is of brick veneer on wood, the building is a wooden building (122), and any failure of the wooden wall will bring down the brick veneer. A New York City fire officer died and a firefighter suffered critical injuries when an interior collapse during overhauling triggered the collapse of an imitation stone-veneered wall. Buildings may have solid masonry bearing walls and veneer nonbearing walls (67) or solid masonry lower floors and masonry veneer above.
In older construction, brick masonry walls showed a course of bricks as headers (ends showing) about every seventh course; veneer bricks show as stretchers (long side showing). Today, all brick walls have stretchers (because of the use of masonry trusses), so it is impossible to tell brick veneer from solid masonry by looking at it.
Many “solid brick” walls contain wooden leveling (or tie) beams on which floor joists rest or wooden lintels over windows. Burnout of the wood causes collapse. Look in the basement or attic to see this dangerous construction, which I have never seen mentioned elsewhere. If you see a picture of a wall segment breaking off along a straight line, the wooden beam probably burned out. One construction book identified this beam as a “tie beam” that is holding the wall together. Masonry wall collapse has killed many firefighters (155-168: “Before the Fire” clues to dangerous walls).
Heavy Timber Construction
It is dangerously incorrect to say that “heavy timber” and “mill construction” are equal. They are not. Mill construction is an ideal design in which all aspects resist collapse from fire and are fully sprinklered. (204) Heavy timber buildings almost universally by initial design or through alteration have many dangerous departures from the ideal mill construction. Heavy timber construction is often called “slow burning.” The better term might be “long burning.” Once defensive tactics are required, the fact that the building will burn for a long time is of no benefit.
Mill and other timber buildings may have “self-releasing floors” lightly tied to columns so that the floors will fall without pulling down adjacent floor sections. Good for the building but bad for firefighters. Unprotected steel replacement columns are common. A collapse of a wood stud wall in a supposed “heavy timber” building killed four Seattle, Washington, firefighters.
In recent construction, very heavy laminated wood beams, which the wood industry publications show to char only moderately, in most cases are found to be supported on unprotected steel columns, which are subject to early failure. (129, 204) Always look at the total GRS (gravity resistance system) for the weakest (to fire) element. (Preplanning Building Hazards in the June issue will address typical potential firefighter killers in heavy timber buildings.)
Wood-Frame Buildings
Modern wood-frame buildings may be structurally considered platform-frame buildings, but because of various voids such as soffits and truss floors that are interconnected by plumbing voids, they are actually balloon frame from the fire point of view. You cannot rely on firestopping. (101)
Some wood and gypsum board assemblies are used in so-called “protected combustible” structures such as garden apartments, where a gypsum board sheath is supposed to protect the wood. The sheath concept is fatally defective. (Chapter 5) The test used, ASTM E 119, Standard Test Methods for Fire Tests of Building Construction and Materials, may give combustible structures of wood and gypsum board equal time ratings. However, S. H. Ingberg, the acknowledged historic expert on fire resistance testing, warns: “We must particularly distinguish between the fire resistance of a combustible and a noncombustible structure. While they may be equivalent in time, there is a world of difference in the protection afforded as it concerns the individual building, the hazard to nearby structures, and the hazard to life.”1
Fire Resistance Rating
The laboratory ratings of relatively small samples of building units cannot be relied on in real-life situations. This widely believed misunderstanding puts many firefighters at risk. When he was president of Underwriters Laboratories, Jack Bono, SFPE Fellow, warned:
“It is dangerous to relate a building`s rated fire resistance to a projected collapse time. The following concept is not correct: `The building has a two-hour rating. If the fire is not controlled in one hour and 45 minutes, prepare to withdraw and operate from outside.`
“Depending upon the fire load, the rate of fire development, and many other factors, such as possible failure of a key structural element or fire barrier, the building may be in distress, or the fire may communicate beyond a fire barrier, in much less than two hours. The converse may also be true. Since there are so many variables, the limit of confidence that one can have is more nearly the concept that a four-hour fire-resistive building is more fire resistive than a two-hour fire-resistive building, and a one-hour fire-resistive building is less fire resistive than a two-hour fire-resistive building. It is not simple to relate the building ratings to an anticipation of what will occur during a fire, either preplanned or actually in progress.” (250)
DO YOU KNOW WHERE YOUR STEEL
TRUSSES ARE?
In Preplanning Building Hazards (De-cember 1998), I showed two pictures of the successful preplanning of a lodge hall with a steel truss roof in Wakefield, Massachusetts. The roof collapsed moments after firefighters were withdrawn. These steel trusses concealed in the attic of theaters, churches, halls–anyplace where a clear span was desired–are a death threat to firefighters. Fire sneaks up into the attic concealed in furred-out lath and plaster walls (usually with 2 2 4 studs) and can burst out furiously. The fire is confined, thus heating the steel more rapidly, and the failure can occur just minutes after fire reaches the attic. Waiting until the fire shows out through the roof may be too late. Conventional venting of the roof may increase the volume of fire in the attic.
Many such attics or cocklofts have no windows that could be used for observation.
I suggest that the preplan for such a building include placing a ladder to the roof, opening an observation hole, and keeping a firefighter at the hole. Any sign of fire in the attic that cannot be suppressed immediately should result in the building`s being cleared.
Get out and look for these catastrophic death traps. Fifty years ago, 13 firefighters died in Brockton, Massachusetts. The same catastrophe could occur in almost any city today.
BIG BOX STORES
Two firefighters died in a North Carolina warehouse fire. Others have died in not very big supermarkets. “Big box stores,” such as Wal Mart, may be as big as 200,000 square feet. Don`t ever get beyond your hoseline in such buildings. Merchandise in foam plastic packing may be heating up, and the whole pile can suddenly ignite. Everything can turn black in seconds. You may have shopped there many times; you may have a great sense of direction, but you are no homing pigeon. Even pigeons get confused. If you get confused, you will probably die.
The entire fire suppression concept in such structures is the “state of the art” sprinkler system. Back it to the limit. If that doesn`t work, consider if lives should be risked because in this case “state of the art” really means “we don`t truly know if this will work, but we are trying it out on you.”
If you do not have a hoseline, use a life line attached to a structure outside the building. Set a big light in the doorway to serve as a beacon. Too many times, a downed firefighter has been found only a few steps from safety. If citizens are reported trapped, the search must be organized carefully, lest the rescuers become victims. How about a blindfolded drill when the store is closed?
Above all, you need the reach and power of a big line. Your experience on residence fires is not adequate. You must study, preplan, and drill on the big potential killers.
THE BUILDING CODE
To the building code authorities, “safety” almost universally means the safe egress of the occupants; rarely, if ever, does it refer to the safety of firefighters. Professor Vincent Brannigan, JD, advises: “In the common law, which is still followed in some states, firefighters are licensees to whom the owner owes no special duty.” This means that firefighters must look out for their own safety.
MORE DECEPTIVE BUILDINGS: UPDATE
In Ol` Professor in the March 1999 issue, I described some New York City multiple dwellings that are so complicated in layout that they are dangerously confusing.
In Loudoun County, Virginia, a developer is building “fourplexes” also called “quadriplexes” or “four corners,” a four-unit condominium that has separate entrances to each unit. The exterior of the building gives no clue as to where one unit meets another. There is no sign of what I consider to be adequate fire separation–a parapeted unpierced masonry fire wall.
In some codes, the requirement for fire separation for condominium units (which are owned) is stiffer than that for rental apartments, on the basis that an owner has more rights than a renter.
In each of these buildings, one unit has a garage or recreation room (most owners opt for a garage) under another unit. It must be fun to realize that in a house you own, somebody else, unregulated by anyone, can accumulate the usual, or even extraordinary, garage hazards right under your combustible home, and you can`t do a thing about it. As I write this, an expensive home in Potomac, Maryland, is heavily involved in a fire that started in the garage. It`s bad enough if it is your own garage, but a careless neighbor`s?
DISCOVERY CHANNEL FIRE SERIES: UPDATE
The Discovery Channel is offering a series on fire, titled “Inferno.” One segment deals with the One Meridian Plaza high-rise fire in Philadelphia in which three firefighters died. A shorter presentation on the same fire is contained in a NOVA presentation “Escape,” which incidentally has much that would be useful for public information presentations.
The Discovery presentation opens with a literally true but very misleading statement. The announcer says that a smoke detector operated, and engines responded. The fact is that the fire almost exactly paralleled the Los Angeles First Interstate Bank high-rise fire. In both cases, security guards repeatedly reset smoke alarms and sent a man to the fire floor to investigate. Both fires were reported when observers blocks away saw flames coming out the windows. In Los Angeles, the man who went to investigate died when he opened the elevator door on the fire floor. In Philadelphia, the guard, lying on the floor of the elevator car at the fire floor, was able to give the guard at the desk instructions so she could close the car door and bring the car down.
Both these stories should be part of your information when dealing with security guard forces. They seem to have an institutional aversion to transmitting alarms. The emphasis on “false alarms” from automatic fire alarms and possibly fines may cause management to order “investigate first.”
In the Atomic Energy Commission, we had clear and strict procedures for the guard force relative to the immediate transmission of any alarm to fire communications. To test the system right from the bottom, I notified Montgomery County dispatch to hold up all alarms from our site for the next five minutes unless I called them. I had my secretary use an emergency phone and excitedly report a fire, giving graphic details. No bells. No announcement. After three minutes, I had her call again, sounding even more urgent. Nothing happened, but the guard lieutenant showed up to “find out what all the excitement was about.” As a result of this test, the security director ordered the entire force to attend a lecture on the absolute requirement for prompt action in such an emergency, without any interjection of today`s beloved personal initiative.
In a real first, the fire-ravaged One Meriian Plaza building has been half torn down to about the 20th floor. I understand that efforts are being made to find a buyer for the remaining half of the building. This story should help to open the eyes of those who do not realize the hazards unsprinklered high-rise buildings pose to life and property. The owners of this building had stalled on complying with retrofit orders. A painter left some oil-soaked rags in an office. A major catastrophe ensued, and three firefighters died.
STUDY GUIDE
I have no connection whatsoever with any Study Guide referring to BCFS3. Note what I wrote on page xviii of BCFS3:
” U. Some asked that a list of pertinent questions be provided at the end of each chapter. This tends to direct readers to study only the answers to those questions, slighting the other material. One problem with this is that everything in the text is important to someone, somewhere. Consequently, it is better to leave the picking and choosing of questions to local instructors or readers familiar with local conditions. I offer a word of caution to those who teach the course and must prepare test questions. In my opinion, the multiple-choice question is dangerous. Its structure requires one answer that appears to be correct but which can be proven wrong. The wrong answer is the one that may flash up in the student`s memory at some critical point, with disastrous results.”
The building is your enemy. Know your enemy.
Endnote
1. S.H. Ingberg was of the then National Bureau of Standards (now the National Institute for Standards and Technology). He developed the concept of applying ASTM E 119 to wood structures and is considered the father of the fire-resistance testing methods.
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The removal of this one ceiling tile completely cancels the fire resistance capability of this “rated floor and ceiling assembly.” The unprotected steel bar joists are subject to early collapse. (Photo by author.)
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(Left) The heat lines on this masonry church wall show how wood stud furring supporting wood lath provides channels for fire to spread from the cellar to the roof. (Above) These sturdy floor beams are level because they rest on a wooden beam in the masonry wall. When the beam burns out, the wall will fall. (Photos by author.)
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The wood industry brags about the charring characteristics of heavy wood laminated beams. Most such beams are supported on unprotected steel columns. Look at the entire GRS (gravity resistance system). (Photo by author).
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Wreckers begin the demolition of the One Meridian Plaza building in Philadelphia. Three firefighters died in the huge fire that occurred in this building in 1991. [Photo by Battalion Chief Greg Collier of the Mt. Laurel (NJ) Fire Department.]
FRANCIS L. (FRANK) BRANNIGAN, SFPE (Fellow), recipient of Fire Engineering`s first Lifetime Achievement Award, has devoted more than half of his 57-year career to the safety of firefighters in building fires. He is well known for his lectures and videotapes and as the author of Building Construction for the Fire Service, Third Edition, published by the National Fire Protection Association. Brannigan is an editorial advisory board member of Fire Engineering.
