What is Roof Sheathing?
The skeleton of a roof is formed with rafters or trusses, generally spaced 16 inches or 24 inches on center (from the center of one rafter to the center of the next) apart. To stabilize the rafters and support the roofing material, rafters are covered with sheathing, or decking. Common roof sheathing materials include the following: Plywood: Plywood, which comes in standard 4-by-8 foot sheets, is strong, durable, and relatively light. It holds roofing nails well. The common grade of plywood for roof sheathing is CDX. As a quick primer in plywood, each side is rated from A to D. A is smooth and knot-free while D, the lowest quality, has missing knots and cracks. One side is usually better quality than the other – C in this case. It should be placed up on the roof. X stands for exterior use. For rafters spaced 16 inches on center, 1/2-inch plywood is standard. For rafters spaced 24 inches on center, 5/8-inch plywood is preferred to minimize sagging. Tongue and groove 2-by-6: These boards
