The listed major components of LWP Roofs include beams, purlins, joists, and decking. Which decking thickness is listed?

• A. 1/2 inch Plywood Decking
• B. 3/4 inch Plywood Decking
• C. 1/2 inch OSB
• D. 3/4 inch OSB

Answer: (A)

In an LWP roof, the decking serves as the solid base the roofing system rests on and as a surface that distributes loads from the beams, purlins, and joists. The thickness is chosen to balance stiffness, weight, and cost. The listed decking thickness is 1/2 inch plywood decking. This provides a sufficient, stable nail surface and adequate rigidity for typical LWP configurations while keeping the roof light. Using thicker plywood would add weight and expense without meaningful performance gains for this system. OSB is not the listed decking type here because the specification calls out plywood, and OSB has different nail-holding and moisture characteristics that aren’t part of this particular listing.