LP. Three rounds of fire testing with inspectors helped FlameBlock Fire-Resistant OSB Sheathing earn a Class A flame-spread rating from UL. Designed to slow the spread of heat and flames in the event of a fire, FlameBlock features a thin coating of nontoxic magnesium oxide cement and fiberglass bonded to the OSB. The fire-resistant coating simultaneously increases the panel’s structural performance. Like other OSB products, FlameBlock resists warping and splitting, and is lighter weight than fire-rated gypsum sheathing. 888.820.0325. www.lpcorp.com.