What is the minimum board size for floor cross bracing?

What is the minimum board size for floor cross bracing?

• A. 19 mm x 64 mm
• B. 15 mm x 60 mm
• C. 25 mm x 75 mm
• D. 12 mm x 32 mm

Answer: (A)

Floor cross-bracing provides lateral stability to the floor by tying joists together so they don’t move apart under loads. To work reliably, the board used must be thick enough to resist bending and wide enough to be securely nailed into the joists and provide proper bearing. The minimum standard calls for a board that is 19 mm thick and 64 mm wide. Among the choices, only this size meets both requirements, making it the smallest board that can effectively serve as floor cross bracing. Thinner boards aren’t strong enough, and narrower boards don’t provide enough bearing or nail area.

Floor cross-bracing provides lateral stability to the floor by tying joists together so they don’t move apart under loads. To work reliably, the board used must be thick enough to resist bending and wide enough to be securely nailed into the joists and provide proper bearing. The minimum standard calls for a board that is 19 mm thick and 64 mm wide. Among the choices, only this size meets both requirements, making it the smallest board that can effectively serve as floor cross bracing. Thinner boards aren’t strong enough, and narrower boards don’t provide enough bearing or nail area.