THE SIGNS OF IMPENDING BUILDING COLLAPSE

BY TOM BRENNAN

We have been reviewing our fire service problem with the integrity of the burning structures. At this time, we have gotten ourselves inside the structure and have been somewhat successful with our attack advance. Remember, the factors surrounding our thought process (size-up) should always and continuously include collapse evaluation, especially if the building is not of framed construction.

Note: Don’t confuse “frame” with wooden buildings. When speaking of collapse, all the buildings in your district can be classified into two categories for collapse safety-framed and unframed. Your preplan or size-up should definitely indicate the class.

Framed construction. You may be asking, “What the heck are you saying?” Well, to digress, almost all buildings to be occupied by humans are designed and built with or without a frame. Framed buildings are constructed by erecting a frame of steel or concrete or any combination of these media. The frame is completed to the height of the finished building (as is the case with institutions, low-rise commercial, hotel, and other occupancies) or to some interim floor, as is the case with true high-rise construction.

Then, floors, supported by the frame, are installed. Finally, walls are hung on the vertical members of that frame. One side thought: Floors have to be in place before the frame rises two stories above the last flooring. The walls, however, don’t have to be finished until the end of the project. This type of structure, then, has the greatest resistance to collapse during firefighting. For “routine” fires, collapse is almost never a probability, although local parts of the building may fail.

Unframed construction. The rest of the occupied buildings in your district are of unframed construction. These are the structures of most concern to the ongoing firefighting effort. As we said at the onset of this column (and if you read the last two columns), we are inside the building. We are concerned with building stability and in particular early signs of building movement. We are the incident commander’s inside eyes and ears. If the command post is indeed listening to us, we are helping to paint the picture of a routine and “safe” firefight or one that is continuing to indicate structural loss, weakening, and probable collapse and that demands that Command change the strategic effort to defensive!

Building movement most times is very subtle. But a moving building is a collapsing building. For what other signs-in addition to cracks, bulges, leaning walls-should we be looking?

Additional signs. Sagging horizontal membranes can indicate an impending full or partial collapse. Some of us never think of ceiling failure as a potential problem. I remember that an entire tin ceiling of a large living room dropped all at once as I touched it with my hook. It slammed my officer into the corner remote from the entrance. He was brought to his knees as he was buried by the “wave of tin.” The lieutenant was the greatest truck officer with whom I had ever worked. As he freed himself and reached the top of the pile, he said to me, “Great pull, kid!” But it can be an entrapment hazard.

Such is the case with the local collapse of suspended ceilings supporting tiles and light fixtures. If the accompanying fireball follows, it can seriously impede your exit effort. Watch the ceilings above you for early sagging. If there is sagging, pull the ceiling as you advance, or it most assuredly will come down after you pass under it.

Sagging floors and roofs. Sagging of more serious membranes and floors and roofs is a special collapse indicator, after a lengthy firefight, from a remote location-an adjoining occupancy in the same building or (heaven forbid) from the outside. If you are standing on the floor or roof, look for puddles. If you walk from one wall to the opposite side wall and your feet get wet, the floor or roof is sagging and “pooling” water. Report it to Command, and determine if dewatering by cutting holes is an option and necessary or whether you should recommend evacuation.

Remember, you must suggest some action to Command. You are the only one who can see the condition. If the level of floors is in doubt, open the walls at the base to inspect the beam ends. Which walls? The two opposite each other supporting the shortest dimension of the floor is a great first choice. Construction engineers are just like us-frugal. They buy the shortest support lumber or steel possible-and this is located between the two bearing walls that are closest to each other.

In dwellings, look at the finished floor. If the wood abutting the walls described above has a “new wood” finish (is lighter in color), the indicator is blatant. The wall is leaving the floor, or the floor is leaving the wall. In either case, give your report as you are exiting the building.

Wall openings. More indicators of building movement can be found in monitoring the openings in the walls-the doors, windows, and passageways. Are they square? Do the doors still fit? Can you close them? Have the windows cracked for no reason? Are the frames square in the window frame? If not, the building is probably moving. Together with other signs of collapse, these are clues that you should change the strategy to defensive as soon as possible.

TOM BRENNAN has more than 35 years of fire service experience. His career spans more than 20 years with the Fire Department of New York as well as four years as chief of the Waterbury (CT) Fire Department. He was the editor of Fire Engineering for eight years and currently is a technical editor. He is co-editor of The Fire Chief’s Handbook, Fifth Edition (Fire Engineering Books, 1995). He is the recipient of the 1998 Fire Engineering Lifetime Achievement Award.

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