The ends of hem-fir wood girders entering exterior masonry walls shall be provided with a minimum _____ inch air space on tops, sides, and ends.

• A. 2 inches
• B. 1/2 inch
• C. 1/4 inch
• D. 1 inch

Answer: (B)

Clearances around wood members that bear into exterior masonry are kept to a small, vented gap to manage moisture. Providing a minimum half-inch air space on the tops, sides, and ends allows air to circulate and moisture to dry instead of wicking into the wood from the masonry. This helps prevent rot, decay, and insect problems and accommodates small movements in the materials after installation. A larger gap isn’t required for this purpose, and a gap smaller than half an inch wouldn’t reliably stop moisture transfer, so the standard minimum is one-half inch.