The Perils of Rain (Double) Roofs

BY BILL GUSTIN

On arrival, firefighters find a one-story ranch-style home with heavy smoke pushing from the soffit vents under the eaves overhanging the home's exterior walls. The battalion chief in command of the incident suspects a fire that has either originated in or extended to the attic. Based on his observation, he orders firefighters, protected by a charged hoseline, to pull ceiling immediately on entering the front door. After forcing the front door, firefighters are surprised to find the house completely clear of smoke but are ready to fight fire over their heads in the attic when they pull the ceiling. When firefighters open the ceiling, they are again surprised and now perplexed to find only light smoke in the attic and no indication of fire. Moments later, the chief reports flames breaking through the roof. What is going on here?

在另一个火在同一细分,交火ers find a house almost identical to the one in the previous scenario with dark smoke pushing from around the hurricane shutters covering the windows. This is a strong indication that the house is not occupied. It is common for winter residents of Florida to install shutters on their homes when they go back North during the hot summer months. The battalion chief, considering the pressure of the smoke and the delay and difficulty in removing the shutters to vent the windows, orders that the roof be ventilated. The chief is confident that the roof can be opened with relative safety because he is familiar with the construction of homes in this area. They were built in the 1960s with roofs of 1- × 4-inch tongue-and-groove sheathing supported by 2- × 6-inch rafters. This older "stick-built" roof is relatively substantial compared to the lightweight truss-supported roofs of newer homes and can withstand several minutes of fire involvement before showing signs of collapse and ultimately collapsing. Firefighters cutting the roof with a chain saw are, as in the previous scenario, surprised and perplexed when they find plywood sheathing instead of tongue-and-groove boards, 2- × 4-inch trusses instead of rafters, and asphalt shingles below their ventilation hole.