Firehouse

JAN 2017

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Request information at Firehouse.com e-inquiry Experience is the difference For more than 30 years, Williams Fire & Hazard Control has successfully faced some of the world's most challenging fires. Our team's front line experience on over 200 major incidents gives them a distinct understanding of flammable liquid fires and the tools it takes to fight them. Learn more www.williamsfire.com Shoulder to shoulder. Copyright © 2016 Tyco Fire Products LP. All rights reserved. Offering a full array of C6 Foam Agents structure members on other types of roofs besides gable roofs, of course. For exam- ple, there are three primary structure mem- bers on a gable roof—the ridge rafter and the two plates supported by bearing walls. On a hip roof, there can be nine primary structure members—a ridge rafter, four plates connecting the rafters to four bear- ing walls, and four hip rafters connecting ends of the ridge rafter to the plates at the four corners. Roof deck construction The weakest part of a roof is the roof deck, which is usually half-inch plywood or tongue-and-groove board between one of four types of roof support systems—timber trusses, plank and beam, solid rafters and lightweight wood trusses. A deck is the first part of a peaked roof to be destroyed by fire, and it collapses during the early stages of a fire. The more unsupported the roof deck, the greater the danger. The fire-weakened roof deck that Lt. Korwatch plunged through was 80 percent unsupported by tongue-and-groove wood deck. The timber truss beams of this com- mercial storage, peaked roof building had 15 to 20 feet of unsupported deck area between timber truss supports. Another roof support, such as a plank and beam, log cabin roof system, can have 5 or 10 square feet of unsupported roof deck between the planks and beams, and a typical solid rafter roof has wood deck 16 or 20 inches between roof rafters, so this roof has less unsupported roof deck area than timber truss or plank and beam. Most flat roofs in the inner city have rafter support systems and provide the best roof deck support; this is not the case on peaked roofs. So the best peaked roof for firefighters is the rafter roof, which also gives firefighters a chance to grab onto a nearby beam if the deck fails. The worst peaked roof is one sup- ported by lightweight wood trusses. This roof system provides no support during a fire. In fact, a lightweight wood truss support system can be destroyed before the half-inch wood deck is destroyed. An investigation of a fire in New York City has revealed that before the deck is destroyed, the sheet metal surface fasteners fall away and truss sections come apart. Further, firefighter fatalities and col- lapse investigations from across the coun- try reveal lightweight truss construction in peaked roofs is too dangerous to operate on when the truss structure is involved. The best strategy is this: If it is just a con- tent fire, use your standard operating pro- cedure. However, if the trusses are burn- ing, use defensive procedures. Do not vent the roof. Fight the fire from the exterior after all occupants are removed. Roof coverings The construction on top of a roof deck is just as important to firefighters as the con- struction below because the roof surface can increase the chances of falling off a peaked roof. As such, firefighters should check the topsides of peaked roofs during pre-fire building inspections. A raised aer- ial platform can be used to closely observe the type of sloping peaked roof covering. January 2017 l Firehouse l 23

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