Which option correctly lists the four major components of LWP Roofs?

• A. Beams (laminated wood or metal); Purlins; 2x4 Joist; 1/2 inch Plywood Decking
• B. Beams; Purlins; 2x6 Joist; 3/4 inch Plywood Decking
• C. Beams; Purlins; 2x4 Joist; 3/4 inch OSB
• D. Rafters; Purlins; 2x4 Joist; 1/2 inch Plywood Decking

Answer: (A)

Lightweight roof systems are built from a simple frame: a beam carries the main load, purlins run along the length to give intermediate support to the joists, the joists themselves are sized for light-weight construction (commonly 2x4), and the deck on top is the surface material (typically 1/2 inch plywood). Beams can be laminated wood or metal, which matches the described configuration. This setup—beams, purlins, 2x4 joists, and 1/2 inch plywood decking—is the standard arrangement for LWP roofs. Other options alter one of these elements (for example, using rafters instead of beams, or specifying OSB or different decking thickness), which moves away from the typical LWP system.