What is the best roof decking material?
Short answer. For most Georgia homes the best roof decking material is either CDX plywood or OSB rated for roof sheathing, at least 7/16 inch thick for 24 inch rafter spacing. Plywood tolerates getting wet and dries faster, while OSB is more uniform and cheaper, and both perform well when the attic is properly ventilated.
The main contenders
- Plywood (CDX). Cross-laminated veneers with exterior glue. Handles a soaking and dries back out with little swelling, holds nails well, and many roofers prefer it for reroofs. Costs more than OSB.
- OSB. Strands bonded with resin and wax. Uniform, no voids, less expensive, and the standard on new Georgia homes. Edges swell if they stay wet, and it dries slowly.
- Radiant barrier panels. OSB or plywood with a foil face toward the attic to cut radiant heat. Useful in Georgia when ducts run through the attic.
- Integrated barrier panels. OSB with a factory water-resistant surface and taped seams, adding protection during construction.
- Tongue and groove planks. Thick solid wood that doubles as a ceiling in cabins and vaulted rooms, usually with rigid insulation and a nail base panel on top.
What matters more than the label
- Span rating. The panel stamp shows a span rating that must match your rafter or truss spacing.
- Spacing and clips. A 1/8 inch gap at panel edges and ends, and H-clips at unsupported edges.
- Ventilation. Either material fails early in a humid, poorly vented attic.
- Fastening. Panels nailed to the framing per code so the deck acts as a diaphragm in wind.
The bottom line
Choose plywood if you want the most forgiving material, OSB if budget leads, and either one in a heavier thickness if you want a stiffer, flatter roof. Read OSB vs plywood roof decking and roof ventilation basics.