Lumber of smaller dimensions needs to be protected by ______ drywall or insulation to increase it's resistance to fire

• A. Gypsum
• B. Drywall
• C. Insulation
• D. Plywood

Answer: (A)

The protective layer used on small-dimension lumber to increase fire resistance is gypsum, in the form of gypsum drywall. Gypsum contains water bound in its mineral structure; when exposed to heat, that water is released as steam, which absorbs a lot of heat and slows the temperature rise of the wood behind it. This endothermic reaction helps maintain structural integrity for a longer period during a fire, giving the assembly a higher fire-resistance rating. Saying “gypsum drywall or insulation” fits the concept because gypsum drywall is the standard fire-protective covering, whereas other insulation materials may provide some protection but do not traditionally perform the same fire-resistance role as gypsum-based coverings.