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Present State & History Of The Building
As fire attacks a building, failure will occur. It can start with localized interior collapse. As fire stops break down, the fire area will enlarge and structural members can become exposed. The destruction of fire stops will cause a much larger area to be affected and increases the danger associated with building collapse.
Collapse indicators include:
- Previous fire damage.
- Windows, doors, floors and stairs out of level.
- Sagging wooden floors.
- Excessive snow or water on a roof.
- Cracking noises coming from a building.
- Interior collapse.
- Plaster sliding off of walls in large sheets.
Previous fire damage. Previous fire damage in a building is cumulative in sapping a building's strength. It creates a dangerous situation for firefighters attacking a fire. The building may be vacant and not repaired from the previous fire and be easily recognizable. However, fire damage may be covered over and remain in walls, floors or ceilings.
Photo by Joe Hoffman
A second-alarm fire rips through a concrete block building being used as an auto body shop. Smoke stains can be seen pushing through joints in the wall and in the vicinity of the lintel beam at the entrance to the shop. The wall collapsed about four minutes after this photo was taken.
Windows, doors, floors and stairs out of level. Observation of windows and doors prior to entering a building should include not only their location for finding a secondary means of escape but whether there are other telltale indicators like doors or windows out of plumb that could indicate a structural problem. Once entering a building, firefighters may find interior doors stuck or jammed due to a building shifting. Staircases that are out of level can indicate a building that has shifted. If the staircase shifts enough it may not support the weight of a firefighter. Firefight-ers finding this condition should keep close to the wall when ascending or descending the stairs.
Sagging wooden floors. Fire conditions can damage floor supports. A wall leaning outward may not be supporting a floor joist that was set in the wall. A sagging wooden floor must be checked to determine whether it is safe to operate on. If possible, a visual inspection of the supports that the floor rests on will assist in the determination.
By checking wall sockets in a wall of ordinary construction or the wooden wall connection in a frame building, the wall's stability can often be ascertained. This can be accomplished by opening the ceiling beneath the floor and checking the ends of the floor boards. Recent movement of the floor joist can be indicated by a swatch of clean lumber at the connection point, or the fire cut on the end of the joist may be visible indicating that the joist is pulling away from the wall's support. The floor joist should be checked at each bearing point to determine whether firefighters can operate safely above.
Excessive snow or water on a roof. Rain water or water from firefighting operations can be retained on flat roofs that have clogged or frozen drains. Though some water on the roofs of exposed buildings can be beneficial in preventing fires from flying embers, a large buildup can be dangerous. Water buildup can reach the height of the parapet walls before overflowing. A tool may be able to unclog the roof drains of debris, ice, or the dislodging or removal of downspouts may alleviate the problem.
Roofs are built to hold the average snow load for the specific region of the country. During winter operations, a buildup of snow and ice on a roof must be recognized. This condition will impair operations. Snow and ice can mask fire conditions normally observed on a roof such as:
- Dry spots where a fire burning below may be attacking roof supports.
- No sponginess would be felt.
- Smoke conditions may be masked.
- The ice itself can act as a platform over a weakened roof area, failing to reveal the hidden dangers below. As firefighters attack the roof to open it, they will break through the ice platform. This action can add a sudden impact load to the roof from the weight of the ice and the firefighters. This sudden weight shift may be sufficient force to cause roof collapse dropping the firefighters into a raging fire below.