Roof decking, also known as sheathing, is the foundational layer of a roofing system that is installed directly over the structural framing of a building, such as rafters or trusses. It is typically made from plywood or oriented strand board (OSB) and acts as the base surface to which all other roofing materials are attached, including underlayment, shingles, metal panels, or membranes. The primary function of roof decking is to provide structural rigidity and distribute loads evenly across the roof frame. It also plays a critical role in resisting wind uplift forces and supporting the overall weight of roofing assemblies, snow loads, and maintenance traffic. In modern roofing systems, proper installation and spacing of decking panels are essential to prevent issues such as sagging, warping, or moisture intrusion. Gaps between sheets are often intentionally left to allow for natural expansion and contraction of wood materials due to temperature and humidity changes. Roof decking must be kept dry and protected during installation because prolonged exposure to moisture can weaken its integrity and lead to mold growth or rot. In many roof replacement projects, contractors inspect decking thoroughly and replace damaged sections before installing new roofing materials.
