Decking

Decking is defined as the structural substrate, typically plywood or oriented strand board (OSB), that is fastened to the roof rafters or trusses and serves as the base surface for the underlayment and roofing materials. Standard roof decking thickness is 7/16-inch OSB or 1/2-inch CDX plywood, though 5/8-inch or 3/4-inch panels are required for wider rafter spacing. Decking must be dry, smooth, and free of defects before underlayment installation, as compromised decking is the leading structural cause of premature roof failure.