Fireground Safety: Collapse Hazards of Overhangs

Miami-Dade Fire Rescue
Fireground Safety: Collapse Hazards of Overhangs
Soffits can be sheet metal, plywood; particularly “T-111” or consist of a thick and heavy layer of stucco applied to wire lathe that hangs from furring strips nailed across the bottom of the overhead. (Miami-Dade Fire Rescue photo)

There are two basic types of overhangs; structural and non-structural. Structural overhangs are a continuation of the roof assembly; such as trusses or beams, that extend over the exterior walls of a building.

Photo 1

(Miami-Dade Fire Rescue photo) 

In photo 1, you can see the roof trusses of this strip shopping center cantilever over the front wall. Similarly, the mansard overhang of the apartment building in photos 2 and 3 is part of the roof assembly. Non-structural overhangs are not an integral part of the roof assembly. A cornice, found on old buildings and false mansards are examples of non-structural overhangs; they are strictly ornamental architectural features that hang on the front wall at or near the roof line. 

Photo 2

(Miami-Dade Fire Rescue photo) 

Photo 3

(Miami-Dade Fire Rescue photo) 

The mansard overhang in photo 4 is fastened to the front wall of an old commercial building with carriage bolts.

Photo 4

(Miami-Dade Fire Rescue photo)  

It was installed to give the old building a “face lift” and to conceal HVAC equipment on the roof but it begs the question: Is the parapet wall capable of bearing the eccentric load imposed by the mansard?

In photo 5 a portion of this nonstructural mansard overhang literally fell off the front of this strip shopping center. As a precaution (photo 6), the building department required the landlord to shore up the entire overhang. 

Photo 5

(Miami-Dade Fire Rescue photo) 

Photo 6

(Miami-Dade Fire Rescue photo) 

If gravity alone can bring down an overhang, imagine the effect of fire blowing out of front show windows. 

Fire officers must keep a close eye on overheads and establish a collapse/no entry zone if they should become out of plumb or begin to separate from the front wall. 

The bottoms of both structural and non-structural overhangs are known as soffits.  Soffits can be sheet metal, plywood; particularly “T-111”  or  consist of a thick and heavy layer of stucco applied to wire lathe (photo 7) that hangs from furring strips nailed across the bottom of the overhead. 

Photo 7

(Miami-Dade Fire Rescue photo) 

In photos 8 and 9, firefighters with pike poles narrowly escaped serious injury when the entire soffit fell in a wave like a stack of dominos. Notice the size and spacing of the furring strips; considering the weight of the stucco and wire lathe, they are relatively small and spaced quite far apart. An assembly is only as strong as its weakest component; in the case of soffits, the weak link is clearly the furring strips.

Photo 8

(West Palm Beach Fire Department photo)

Photo 9

(West Palm Beach Fire Department photo)

Fires can originate or extend to an overhead. To open an overhead, firefighters often attempt to pull the soffit with pike poles. Penetrating and pulling a stucco on wire lathe soffit under an overhead can be very difficult, dangerous, and often unnecessary. 

For example, if the overhead is structural it is often possible to gain access and direct streams into it from an opening in the interior ceiling. To conserve air conditioning, it is common to find the structural overhead separated from the interior ceiling space with plaster board or foil-backed insulation board; both easily penetrated with a pike pole.

If an overhang extends above the level of the roof, the safest and least damaging way to open it is from the back, providing that the roof is structurally stable. An alternative is to open a gable end. In rare cases when there are no alternatives, firefighters attempting to pull soffits should look for vent openings or recessed light fixtures to gain an initial purchase point and use 10 – 12 foot pike poles to stay out of the collapse zone. Remember, a large portion of stucco on wire lathe can fall in one piece; as in photo 9, so no one should be operating under the overhead when firefighters are attempting to pull a soffit.



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