Ceilings and Suspended Loads
FEATURES
BUILDING CONSTRUCTION
Making pre-plan surveys? Do something different. Look up. Look at the ceilings. Look for suspended loads. Check your checklist. Does it even mention ceilings or suspended loads? What’s so important about them? Two four-letter words: THEY can KILL.
I’d love to give you one of those popular “All you need to know on one-page articles” for the busy reader, but I can’t. The subject is not that simple. So you have a choice. Either pass this article up and someday you may be the star of an article about the firefighter killed in a “sudden flashover” or “collapse without warning”; or hunker down and store some lifesaving data in the marvelous super PC we call the brain.
There are four principal considerations when sizing up ceilings:
- Flame spread over the ceiling,
- Ceiling collapse,
- Voids above the ceiling,
- Suspended loads.
As usual, there are many interrelationships; the divisions are not cut and dried, but they help us understand the problem.
OLD CEILINGS
Not too many years ago, there were only three ceiling materials: plaster, wooden matchboarding, and embossed steel, which was often called “tin” ceilings.
Plaster
Plaster was usually applied on wood lath, and for a number of years after its application, would resist the passage of fire. As the plaster’s moisture dries out, however, it tends to fall early in the fire, exposing the combustible wood lath. When fire penetrates the void, it finds a ready supply of fuel. The wood lath represents a tremendous fire load, easily ignited, with a high RHR (rate of heat release); it burns very rapidly.
Falling plaster at the fire scene, particularly if it’s in an area not directly exposed to fire, may also signal that the joists are moving, a sign that collapse is imminent. Immediate evacuation is called for. Ornamental plaster can fall in very heavy chunks.
Plaster on metal (wire) lath was used where some degree of fire containment was required. In one case, a workman pulled loose metal lath on the top floor of a building that had been added to over the years, increasing from one to five stories. The wire lath sheets were literally holding the building together. Pulling the lath caused the building to collapse.
Wire lath and plaster are also used as part of some rated fire resistance systems. Wire lath is extremely difficult to remove. Call for additional assistance if extensive removal of wire lath is necessary.
Today, plaster is most often installed on gypsum lath, sheets of gypsum board similar to the familiar drywall.
There have been advertisements for a plastic imitation of the old decorative plaster ceilings. No information was offered as to their fire characteristics. If these ceilings are scheduled for installation, flame spread ratings should be required.
Wooden matchboarding
Wooden matchboarding is thin tongue and groove boards with a moulding design milled into the surface. It is readily combustible and gives little resistance to the passage of fire.
Embossed sheet metal
Embossed sheet metal (“tin”) ceilings were, and still may be, required by some codes on the erroneous concept that steel, being non-combustible, would stop the passage of fire. Steel, of course, transmits heat by conduction in both directions. I saw flaming paint, ignited by conduction from a cockloft fire, fall from the tin ceiling into flammable merchandise below. The fire quickly spread throughout the store. In addition, metal ceilings are difficult to pull to expose fire. They also have been known to cause nasty lacerations to operating firefighters.
RESTORATION
All these types of ceilings still exist. In some restorations, authenticity is insisted upon, and old tin ceilings in good condition command premium prices. In one case, one tin ceiling was installed below another, making two impenetrable voids. Few “authentic” restorers go so far as to insist on wood lath, however. Where wood lath is deteriorated, gypsum lath is used. Where buildings are merely being rehabilitated, gypsum board (drywall) is usually used.
Since older buildings have higher ceilings than do present-day structures, it’s common to “drop” a new ceiling well below the original in older, high-ceiling buildings in order to hide utilities. This creates huge interconnected voids. A fire in a factory building that had been converted into apartments, seized control of the interconnected voids. Sixteen truck companies were required to locate the fire in the voids. Typical firestopping is non-existent in these voids, and where sprinklers are provided, the void is rarely protected. A college dormitory was rehabilitated with a new dropped ceiling, below which sprinklers were installed. The old wood lath and plaster ceiling had been penetrated in many places. A fire broke out, roared through the voids, and destroyed the structure.
FIBERBOARD
Fiberboard, developed more than 50 years ago, was initially used in cheaper construction, since it could be erected quickly and provided some heat insulation. Joints could not be taped very neatly, and were often covered with flat wood strips. The board is easily ignited, burns tenaciously, and appears to move from moderate burning to explosive flashover in a matter of seconds.
The failure to recognize the extreme hazard of leaving this material in a structure being burned for a drill fire was a major contributing factor to the loss of three Colorado firefighters. Many years ago, a Maryland firefighter lost his life in a drill building burn. Combustible fiberboard tile was the cause. Since then, the Maryland Fire and Rescue Institute has required that all fiberboard be removed from a building to be burned. Low-density fiberboard (often described as celotex) is easily ignited by the heat of a defective fluorescent fixture. For instance, a 100-watt bulb that was in contact with fiberboard started a destructive computer area fire at the Pentagon Building in Washington, D.C. (Because of fear of water damage, the area was not sprinklered. However, the guard had been provided with a CO2 extinguisher, which did no damage—particularly to the fire.) Fluorescent fixtures should be (but often are not) installed away from such a surface providing sufficient insulating air space. Similar material, usually colored black, is used for combustible sheathing. It has often been ignited by a plumber’s torch.
COMBUSTIBLE ACOUSTICAL TILE
Low-density combustible acoustical tile provided an attractive, sound conditioning, easy to install, rehabilitation material for deteriorated plaster ceilings. The fire protection profession was slow to assess the hazard. A study of pictures of Boston’s Coconut Grove disaster in 1942, in which 492 people died, clearly shows that the ceiling had been covered with combustible acoustical tile. This fact, however, completely escaped the investigators. Shortly after World War II, Bob Moulton, the secretary of the National Fire Protection Association (NFPA), wrote the first document on combustible acoustical tile. This provoked the typical storm of protest from the industry whose answer to the material’s fire hazard was a cornstarch coating on the tiles which resisted the “raging flame” of a half-thimbleful of alcohol.
Combustible tile was installed in a midwestern hospital. The hospital management, alarmed by complaints that the tile was hazardous, sought and received written reassurance from the manufacturer. The hospital burned with a huge loss of life, but the letter survived. The manufacturer agreed to a very substantial settlement.
It is true, unfortunately, that judgements or huge settlements (and the potential for many more) are often required before an industry will agree to a safety standard.
There is a realistic standard measuring flame spread on materials such as those used on ceilings. The standard is ASTM (American Society for Testing Materials) E 84, the so-called Steiner Tunnel Test, named after A1 Steiner, a dedicated Underwriters Laboratory (UL) engineer who developed it. The test measures the degree of flame spread and provides the code official with a tool to restrict the spread of flame on ceilings in critical areas.
Combustible tile was blamed (possibly incorrectly) for the loss of life in Chicago’s Our Lady of Angels school fire in 1958. This fire caused the Los Angeles Fire Department to conduct tests that graphically demonstrated the hazard of acoustical tile. Acres of this tile were subsequently removed from school buildings.
From time to time, you may read a graphic account of a “flashover,” or a “sudden burst of fire,” in an article that tells you the name, rank, and serial number of the officer who ordered water started, but nothing about the buildings. In such a case, it is a good bet to assume that a combustible ceiling and its associated void space was involved. Just such an article told of a firefighter who died in a flashover in a fire resistive YMCA in Reading, PA. A letter from the author confirmed my surmise that a combustible acoustical tile ceiling suspended on a grid was the cause of the flashover.
Several years ago, I watched a fire in a laundromat that was situated in a row of stores. The laundromat had a combustible tile ceiling mounted on a wooden grid, providing a three-foot cockloft above. The ceiling surface was swept with a 2!^-inch stream and all appeared clear except for one persistently burning tile. Some time later, there was nothing but dense black smoke, one pre-signal of a backdraft. Shortly thereafter, the adjacent store exploded. Fortunately, emergency personnel were only knocked down.
If the ignition of carbon monoxide (CO) in a void is a detonation rather than a deflagration (see NFPA HANDBOOK 15th edition, page 3-15), it can destroy the building. If combustible tile is observed, determine if there is a void above. Extinguishing the visible ceiling surface does not extinguish the fire burning on the back side, and there is serious risk of a flashover or backdraft explosion.
In Orlando, FL, firefighters escaped with turnouts burning, when fire suddenly burst from a void above a fiberboard ceiling. Elsewhere, three firefighters died in a furniture store fire. It appears that there was insufficient recognition of the hazard of combustible tile ceilings and the associated void space. “Light smoke showing” may soon be followed by flashover.
Today, you cannot consult a catalogue for a ceiling tile material for commercial use without being informed as to the flame spread rating, so universal are code requirements. (This is not generally true of the household market, but boxes are often marked with the flame spread rating.) There is a real deficiency in code requirements, however, when buildings are remodeled.
REMODELING
Many thousands of square feet of old combustible tile is still in place, but not visible. When buildings are remodeled, very often new suspended ceilings which meet code requirements are suspended below the old deadly tile ceiling. The old tile ceiling should be removed, but codes do not generally address this tremendous hazard. In Wyoming, MI, old tile ceilings are now required to be removed because of the deaths of two firefighters.
Most building officials and contractors look blank when queried about the presence of tile ceilings. Fight to get the old ceiling out. Play hard ball if necessary. Get the owner and tenants upset. Tell them that because of the hazard to firefighters, you will be compelled to use large quantities of water, which would not otherwise be necessary. Politicians mindful of the campaign contributions of builders and developers may tell you not to be picky, or to “just stick to the code,” but it takes a politician with brass eyeballs to look you in the face and tell you that he is not concerned about the lives of firefighters.
Old buildings may have several layers of ceiling. We noted earlier that ceilings were high to allow for summer ventilation. In successive alterations, ceilings were dropped. Carefully examine any area in an older building with low ceilings. You will probably find a series of combustible voids, one above the other. A full first-alarm assignment searched for 45 minutes in a century-old building for a fire hidden in the highest of four ceilings.
ADHESIVE
In a New England hospital, a corrider, overhead pipe-chase was concealed by a gypsum board ceiling. Combustible tile was glued to the gypsum board. Alarmed at the hazard, the hospital had the tile painted with an intumescent coating. Fire roared out of a laundry chute and down the corridor on the ceiling. Sixteen people were killed. It was determined that the combustible adhesive increased the flame spread of the tile tremendously. The MGM Grand Hotel in Las Vegas, NV, had 12 tons of combustible adhesive holding up tile.
In my opinion, it is impossible to “flameproof” combustible tile in place. If it is glued, the hospital fire demonstrates the hazard. If it is nailed to stringers, there is a hidden combustible top surface over which fire spreads very rapidly.
CARPETING
It is not uncommon to have ceilings decorated with carpeting. Be very suspicious of all carpeting. Only recently have test ratings become available for carpeting, and the hazard is often unrecognized. The standard is NFPA 253. When last I looked, the sales room at the Lincoln Memorial in Washington, D.C., was sheathed in carpeting— walls, floor, and ceiling. Flammable carpeting on the ceilings of the elevator lobbies spread fire with lightning speed up the face of the Las Vegas Hilton. Few interior designers are aware of the hazard.
FLAMMABLE CEILING DECORATIONS
One of the most disastrous fires in history took place in a South American cathedral. The overhead was decorated with sheeting to represent clouds. It ignited and hundreds of worshippers were killed.
While at lunch with a fire marshal, I was shocked to learn that the ceiling was covered with loosely hung burlap. “Think nothing of it. The place is sprinklered.” He found it hard to believe that a fire would spread over the burlap far faster than the sprinklers could operate.
Be especially alert for “haunted houses” set up by well-meaning civic groups to keep the kids out of Halloween mischief. It seems that the first thing they think of is cotton sheeting—with electric lights behind it.
PLANK AND BEAM ROOFS
Many places of worship, other buildings of public assembly, and some open construction, private dwellings built in recent years have wooden “ceilings” as the underside of exposed plank and beam floors or roofs. These have the advantage of eliminating the void space. The disadvantage is that fire can spread with startling rapidity over the surface. The spread can be accelerated by the use of flammable surface treatments. If the structure is unsprinklered, a fire may result in a total loss in a very short time.
The fire loss management solution is to avoid setting the ceiling on fire. This is accomplished by sprinklering or eliminating combustible sub-structures such as sacristies, robing rooms, concession stands, rest rooms, and any other mass of kindling capable of igniting the ceiling/roof.
A raging fire involving a plank ceiling can be controlled if the fire department arrives before the building is fully involved, doesn’t write the building off, and has preplanned its strategy, tactics, and procedures properly.
Firefighting plans should provide for heavy caliber, long reach streams, positioned so as to sweep the entire surface. The stream should be solid rather than fog so it is not eaten up by the fireball. This plan worked perfectly when the Killarney, FL, Fire Department (now Orange County 41) suppressed a raging surface fire in St. Charles Church in 14 minutes.
GYPSUM BOARD
Gypsum board is not the most commonly used ceiling and wall surface material. (The trade name Sheetrock is often erroneously applied to all gypsum board.)
Gypsum is a wonderful material. It is the only building material that absorbs (endothermic reaction) rather than yields heat energy (exothermic reaction) when tested in pure oxygen. When fabricated into the familiar gypsum board, however, it is slightly exothermic, due to the paper surfacing and binders.
Gypsum board is woefully misunderstood. Some gypsum board is listed and labeled by UL as being suitable for use in listed “fire resistive (combustible) assemblies.” This does not mean that the gypsum board can be separated from the tested and listed assemblies. UL specifically warns against taking an element out of a listing. The listing includes all the elements as constructed for testing in the laboratory. In other words, you cannot make a structure “fire resistive” just because you nail up some gypsum board.
Specifically, all tests are conducted on structures that have a limited air supply in the void above the board. When the wood heats to fire temperatures, the oxygen available to support combustion is limited. When gypsum board is nailed to a void in which the oxygen supply is huge or unlimited, as in a ventilated attic, the conditions of the test have not been met, and the structure cannot be considered to be equivalent to a rated structure. In other words, “one-hour fire resistance” is not achieved simply by nailing up “rated” gypsum board. To be truly “rated fire resistive” the structure should be identical to the structure tested.
Taping and nail setting are believed by many to be simply cosmetic. They are, in fact, a necessary part of the fire resistance system.
In addition, there are many quite legal penetrations or pinholes in the gypsum sheath, not tested in the laboratory, that will admit fire to the void. There isn’t anything we can do about this, except to recognize that fire will penetrate the void very much faster than we might be led to believe.
Gypsum board that is rated by UL is subject to follow-up inspection procedures. Periodically, UL inspectors take a sample from the production line and send it to UL for testing. The cost of the original listing and the follow-up procedure amounts to less than one cent per sheet. Just the cost of testing alone would not justify all the problems of carrying two separate product lines. There is a substantial difference between rated and non-rated gypsum board.
While it is not possible to create a fire resistive structure simply by applying some gypsum board, it is true that board that bears the seal of a recognized laboratory is superior in fire characteristics to unlabeled board of equal thickness.
SUSPENDED GRID CEIUNGS
There are a number of rated fire resistive “floor and ceiling” assemblies that incorporate a suspended grid ceiling as part of the total assembly. These are often confused with ceiling panels with low flame spread ratings which are used to meet flame spread requirements. These are widely used because they are easy to install and eliminate the mess made by taping cement or paint.
The term “fire rated ceilng” usually refers to a ceiling that meets only flame spread requirements and does not provide fire resistance. Even a ceiling which is the same as the ceiling component of a rated floor and ceiling assembly does not by itself provide rated fire resistance, because components are not rated separately. The assembly is rated as a whole. A combustible structure, therefore, cannot be considered protected because a so-called “fire rated” ceiling has been installed.
It is a common practice to install insulation batting above the ceiling on the uppermost floor to conserve energy. The inherent fire resistance, whatever it might be, is diminished. The insulation causes heat to be retained in the steel stringers, so they fail sooner than they would otherwise.
VOIDS
Consider a response to a typical free-standing fast food outlet. The roof is of plywood on wood trusses. The ceiling is gridded tile which meets flame spread requirements. “Light smoke is showing.” It appears to be coming from the ceiling space.
Opening the ceiling at random may prove disastrous. The smouldering fire suddenly gets a burst of oxygen; a backdraft occurs and the ceiling is blown down. Firefighters are trapped by the grid, like gladiators in the opponent’s net. Completely unprepared for this condition, the firefighter may thrash around in the pitch blackness until air is exhausted. This appears to have been the scenario in at least one fatality. Personnel should be trained to drop down under the level of the floor fixtures, to stay below the net.
A ceiling void should be opened only by personnel under strict control, close to escape routes. This operation can be the equivalent of pulling the wires off a suspected bomb.
SUSPENDED LOADS
When the writer of a mystery novel involving a theater can’t think of what to do next, a heavy piece of scenery mysteriously falls from the overhead.
Firefighters are now subject to the same danger.
Suspended loads are becoming more common. Architects are aware of the advantages of loads in tension rather than compression. Interior designers appreciate the fact that floor space is uncluttered.
The method of suspension of Decorative items is often of no concern to the building department, as they are not part of the structure. The connection can be extremely vulnerable to attack by fire. The overhead load can be very substantial. It is more and more common that parts of the structure, such as church balconies, are suspended.
I examined an Anne Arundel, MD, library where the mezzanine is supported on a beam which hangs from a roof truss on a slender steel rod. Since the building is not required to be fire resistive (and thus is entitled to collapse in a fire), a fire can cause the connection to fail quite early, and thus the mezzanine to collapse. Something like this appeared to be the case in a California interior collapse. A request to the chief for information to confirm or contradict the surmise brought the unfortunately usual non-reply.
As a general rule, temperatures in a fire are far greater in the overhead than they are at floor level. The heat may be bearable on the floor, but sufficient to destroy connections above. The “cocooning” of the firefighter by protective apparel appears to make him less sensitive to hazardous environments. It might be useful to remove a glove, raise the arm and get a feel for the ambient temperature.
A UNIQUE FIRE
I observed a $250,000 fire in a literally non-combustible (almost) supermarket in which not so much as a bag of potato chips burned.
The walls are masonry. The roof is gypsum on bar joists. The ceiling is fiberglass tile on grids. Above the meat section in the rear, a wooden structure had been built to provide a nailing surface for the washable gypsum ceiling required by the health department, and to suspend the heavy overhead refrigeration units. The electrical fire extended only to the wooden structure. The heat was sufficient to collapse the roof. The fire was completely out.
A truck company was pulling the ceiling. I asked them to step back, and for one firefighter to remove the plaster board from around the plumbing strap which held the refrigerator so that I could photograph the poor connection. As he touched the gypsum board with the pike pole, the heavy unit fell.
I am not the first to point out the high proportion of firefighter deaths which occur when overhauling. Why do we have this burning desire to finish the demolition started by the fire? In the supermarket, as in other cases, the fire was dead out. There were no “hidden pockets of fire to seek out.”
TAKE CARE
There is much discussion of the new super dooper helmets. Do not put excessive faith in them. The human body can take just so much. If the load is excessive, the frontispiece of the helmet becomes your belt buckle.
The psalmist wrote, “I lift up mine eyes unto the hills, whence comest my strength.” Firefighters are well advised to lift up their eyes to the overhead and study it. Your life may depend on it.
