BY FRANCIS L. BRANNIGAN,SFPE (FELLOW)
Editor’s note: For further reference, consult Building Construction for the Fire Service, Third Edition (BCFS3). Page numbers, where applicable, are included after the caption.
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▲ Heavy timber has an undeserved reputation in the fire service for safety. Study the difference between true mill construction and code-specified heavy timber. They are not the same (see BCFS3, 204). See also “The Dangerous ‘Five Classes of Buildings,’ ” (Ol’ Professor, Fire Engineering, May 1999, available at emberly.fireengineering.com).
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▲ The sprinklers in this heavy tim- ber building had been disabled; the occupants had smelled smoke for hours before call- ing 911, so this structure was a to- tal loss. Note the big line directed not on the fire but to wet down an ex- posure (photo by Harvey Eisner).
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▲The wood in-dustry publishes material compar- ing a charred lam- inated wood beam with a steel beam twisted from fire exposure. How-ever, do note that many, if not most, laminated wood beams are supported by unprotected steel columns, in this case hidden in a plywood wall. Trace the load to ground, and determine the element in the Gravity Resistance System (GRS) that is most vulnerable to fire-caused failure. Note also the lightweight brackets that attach the floor beams to the laminated wood “girder,” a beam that supports other beams.
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▲ This mortise-and-tenon (think “tongue”) joint, the pride of the framing carpenter, will fail if the tenon burns out.
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▲ The only dependable protection for a heavy timber building is a properly designed, maintained, and supplied automatic sprinkler system. I am aware it is a radical idea, but I believe the first line should go into the sprinkler system to augment the volume and pressure.
• The sprinkler knows where the fire is; you may be looking for it.
• The sprinkler is really your first line on the fire.
• Do not be in a hurry to shut down the sprinklers, to “see the fire” or limit water damage. The firefighter shutting down a valve should stay there and be in radio contact. Fires have a habit of breaking out in full bloom.
• Be fully aware of all the necessary INFORMATION ABOUT THE SYSTEM. It is not just “the management’s problem.”
• Study Chapter 13 in BCFS3.
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▲ This mezzanine was built in a sprinklered store. Unless sprinklers are located in the ceiling under the mezzanine area, a fire that can overpower the sprinkler system can develop. This is another good reason for early hookup to the sprinkler system. The increased flow may be adequate to prewet the surrounding area and prevent extension, even though the sprinklers are not hitting the “protected” fire.
■ FRANCIS L. BRANNIGAN, SFPE (Fellow), the recipient of Fire Engineering’s first Lifetime Achievement Award, has devoted more than half of his 63-year career to the safety of firefighters in building fires. He is well known as the author of Building Construction for the Fire Service, Third Edition (National Fire Protection Association, 1992) and for his lectures and videotapes. Brannigan is an editorial advisory board member of Fire Engineering.
