BY SCOTT JOERGER
Modern construction techniques and lightweight wood construction are not new. Wood roof trusses have been around since the 1960s. Modern construction refers to a newly built structure or a structure that has undergone significant renovations. Lightweight wood construction refers to engineered wood products used in modern wood-frame structures; they have less area mass and are lighter than components used to build older houses. Firefighters have been faced with additional challenges in modern wood-frame structure fires as the buildings have become more and more lightweight. Today, wood trusses and wooden I-beams are used as framing or structural members; thin boards are used for sheathing or decking made of 4- by 8-foot oriented strand board (OSB) and plywood; and dimensional wood pieces are used for studs, joists, and beams that are different in size and time to failure under fire conditions than the wood components used prior to World War II.
此外,当前的建设和施工techniques allow for a rapid spread and propagation of fire. Examples include attic and soffit vents, which draw in large quantities of fresh air, permit exterior fire to quickly enter the attic space, and burn easily in the truss space and exterior finishes that readily ignite or melt away and expose unprotected wood sheathing, enabling exterior fires to quickly race up the building's surface. We encounter modern wood-frame construction mostly in residential homes, but these construction features are also seen in other new buildings, including office buildings, places of worship, and strip malls where a sprinkler system may or may not be present. If one is present, it is not usually in attic spaces and on the building's exterior. When responding to fires in modern wood-frame buildings, a fire that has extended beyond the room-and-contents fire has a great potential to develop rapidly; spread to exposures; and cause structural members, floor or roof decking, and exterior wall sheathing to fail early (photo 1).
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