An often confusing issue is whether a re retardant paint or coating on OSB with a Flame Spread Index of 25 or less is the same as re-retardant-treated plywood. The distinction between these products becomes even more critical when the roof system is used in noncombustible construction. One of the most important aspects to remember is this: Pressure impregnated re-retardant-treated plywood was developed as an alternative to metal roof decks, it is given comparable insurance rates and re-retardant-treated wood roof systems are suitable for the same uses. On the other hand, OSB products which claim to be the same as re-retardanttreated plywood have not been tested in the full scale test and their performance has not been evaluated in comparison to the Fire Classi ed unprotected metal deck. For more than 100 years the wood preserving industry has produced wood pressure impregnated with reretardant salts to enhance wood’s performance in re. Pressure impregnating lumber and plywood with reretardant treatments imparts properties important to re safety. Fire-retardant-treated wood does not support combustion and there is no signi cant glowing after ames are removed. Also, re-retardant treatments substantially reduce the combustion rate of wood while at the same time limiting ame spread.
PRESSURE IMPREGNATED
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Table of Contents for the Digital Edition of NFPA Journal - September/October 2012