Structural Firefighting Operations: Collapse

Collapse During Structural Firefighting Operations

• This manual chapter provides general information about collapse during structural firefighting operations
• Each member is responsible for exercising appropriate control as dictated by their rank when implementing this manual chapter

General Information

• Collapse is defined as shrinking together suddenly, caving in, falling in, breaking down, folding, or pushing together
• Firefighters can expect more structural collapses due to building age, abandonment, lightweight construction, and faulty renovations
• Safety on the fireground is everyone's responsibility
• Any warning signs of collapse should be reported to the Incident Commander immediately
• Warning signs include: bulging walls, large cracks in masonry walls, leaning walls, creaking sounds, doors and windows not square in the frame, smoke or water from cracks/ missing mortar, water not exiting (being absorbed)

Construction Collapse Hazards

Type I Construction

• The primary collapse danger in a fire resistive building lies in concrete
• Heated concrete ceilings in reinforced concrete buildings can spall when water is applied, causing large sections to fall
• This can happen when concrete is not protected by a suspended ceiling
• Heated concrete floors in steel skeleton buildings can crack or sag

Type II Construction

• The primary collapse danger of a noncombustible/limited combustible building is from a truss roof cave in
• Other hazards include the collapsing material and unprotected steel open web bar joists

Type III Construction

• The primary collapse danger in ordinary brick and joist construction is the parapet wall and bearing wall failure
• This will cause floors to collapse along with the wall

Type IV Construction

• The primary collapse danger in heavy timber construction usually occurs later in firefighting operations
• Floors will collapse from fire impingement and water weight and push walls out into the street, throwing bricks
• This type of collapse also causes severe damage to surrounding buildings as the walls fall onto the roofs of other buildings in its path

Type V Construction

• The primary collapse hazard of a wood frame building is in its combustible bearing walls
• Side walls are typically bearing walls, while front and back walls are non-load bearing
• Approach flames from multiple windows on a side bearing wall with caution, as the fire is attacking the combustible bearing wall
• Collapse of this wall will trigger a collapse of the roof and floors inside

Masonry Wall Collapse

• Masonry walls can fall in three ways:
  • 90-degree collapse: like a tree falling; collapse zones should be 1.5 times the height of the building
  • Curtain fall: the wall falls straight down
  • Inward/outward collapse: the top falls inward and the bottom kicks outward.
• Facades (front walls) are another danger
• Monitor parapets, cornices, marquee signs, and canopies for collapse potential

Wooden Floor Collapse

• This type of collapse is a leading cause of firefighter deaths
• Floors fail three ways:
  • Floor deck collapse: deck burns through, but joists hold
  • Floor beam collapse: localized failure, floor fails in a lean-to or V-shape
  • Multi-level floor collapse: upper floor collapse causes a domino effect (pancake collapse)
• Multi-level collapses are typical in buildings with a frontage over 25 feet, requiring columns and girders
• Three reoccurring themes are vacant, renovated buildings, and buildings with large amounts of contents or machinery stored on the floor

Ceiling Collapse

• Ceiling collapses do not cause structural collapse but are dangerous
• Ceilings are either affixed directly to the structure or suspended "drop" type
• Suspended ceilings are most dangerous because if hangers/supports are attacked by fire or pulled down, large sections weighing thousands of pounds can crash down
• Firefighters can get entangled in wires or be cut off from egress

Stairway Collapse

• Stairways are dangerous for firefighters
• Fire/weight of firefighters can weaken them and cause them to fail
• If a stairway is supported by a bearing wall, it should withstand a floor collapse
• If a stairway is supported by the flooring system, it will collapse if the floor fails
• Limit the number of members on stairways, especially when weakened by fire or the floor shows signs of collapse

Fire Escape Collapse

• Any addition affixed to the side of a building exposed to the elements should be considered suspect
• Size up fire escapes before using them
• Examine bolts attaching the fire escape to the wall and the stairs to make sure the treads are present and intact
• If bolts/treads are rusted/missing and there is no immediate life hazard, use fire department ladders instead

Flat Roof Collapse

• To determine the potential for a flat roof to collapse consider the type of support system in use
• Buildings with steel bar joist construction, lightweight trusses, or wooden I beams will fail faster than ordinary solid wood joist construction
• Second factor is how the roof is connected to supporting walls
• Roofs built into a brick cavity may hold up on the ends while the center burns away, so firefighters should walk near the parapet wall
• Unrestrained beams resting on a girder have a high potential to rotate off supports and slide down into the center
• Third factor is if there is a built-up structure (inverted/rain roof) above the main roof supports
• These may rest on a smaller wooden support system that could be attacked by fire

Peaked Roof Collapse

• Peaked roofs collapse when one of its structural members are attacked by fire
• A peaked roof has nine primary structural members: four bearing walls, one ridge rafter, and four hip rafters
• Operations on this type of roof are extremely dangerous
• If the fire is not directly under the roof in the attic, then opening the roof will do little to assist with ventilation
• If the fire is directly under the roof in the attic, it should be assumed the structural elements are being attacked and members should not be operating on the roof

Truss Roof Collapse

• When supports of a truss system are attacked by fire, they cause a failure of a portion of the truss roof, this span can be very large
• Truss roof failures have caused multiple Firefighter Line of Duty Deaths
• When the Truss Roof fails remember that lives of the firefighters on the roof are not the only ones in danger
• Members under the truss roof, and or outside can be crushed by the collapse
• Any suspected fire impingement on a truss roof requires change in tactics, members must check to see as early as possible and relay the information to the Incident Commander