Preplanning Building Hazards
BY FRANCIS L. BRANNIGAN,SFPE
Editor`s note: For further reference, consult Building Construction for the Fire Service (BCFS3), Third Edition. Page numbers, where applicable, are included after the caption.
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(Left) Pre-World War II high-rises characteristically had wet masonry block and brick panel or curtain walls built in a concrete floor. This was excellent inherent firestopping.1 There were a few well-firestopped penetrations. Fire and smoke migration were limited, but modern practice uses precast concrete or imitation concrete panels for speedier and cheaper construction (middle). In this case, the “firestopping” meets my definition of legal firestopping2 and consists of (right) the light blue “inhibited” polystyrene panels (chemicals were added to reduce or stop flame spread). The building department permitted the use of the panels because of the flame-resistant characteristic, ignoring the fact that they will melt away. One solution would be to do just what sprinklers would do–flood the floor with open hose butts. Water pouring down all the voids will act as what can be called dynamic firestopping–the stopping of fire from coming up. This technique was used decades ago in brick and wood-joisted buildings with multiple floor openings. Be ready to point out the responsibility for the “water damage.”
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This business extends into two buildings, on the ground floor. The original bearing walls, eight or 12 inches of brick each, are still in place on the upper floors. Is this weight supported? What is the fire vulnerability of the support? The key to Boston`s Vendome nine-fatality collapse was the fact that a bearing wall had been removed and replaced with a beam and cast-iron column, which I have referred to as “the hidden wall trick.”
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One method of supporting the hidden wall was a steel beam supported by a cast-iron column but not connected to the column. When heat distorted the beam, the beam fell off the column.
Endnotes
1. This type of firestopping results from the normal building construction; it is incidental to necessary structural purposes–for example, the floor-to-wall seal when a masonry panel wall is built directly on a concrete floor. It is reasonable to assume that such inherent firestopping is in place and effective. BCFS3, 107.
2. Firestopping installed with no other purpose than to meet the requirements of a code. It may provide a barrier to the spread of fire in the building`s interior voids. However, it often is ineffective. Questions such as the following will always be asked pertaining to this type of firestopping: “Was the firestopping properly and completely installed?” “Was the building inspector competent and vigilant?” “Was it tampered with after installation?” BCFS3, 107.
FRANCIS L. (FRANK) BRANNIGAN, SFPE, recipient of Fire Engineering`s First Lifetime Achievement Award, has devoted more than half of his 57-year career to the safety of firefighters in building fires. He is well known for his lectures and videotapes and as the author of Building Construction for the Fire Service, Third Edition, published by the National Fire Protection Association. Brannigan is an editorial advisory board member of Fire Engineering.
