What is the best option for roof decking?
The four real options
- Keep it. A sound deck that holds nails, has no soft spots and lies reasonably flat stays in place. This is the case on most roofs.
- Spot replace. Bad sheets are cut out to the rafter centers and new panels of matching thickness go in. This is the normal reroof approach.
- Overlay. Old plank decking with gaps, or a deck riddled with old nail holes, gets a layer of new OSB or plywood fastened over it to create a uniform nail base.
- Full redeck. Everything comes off down to the rafters. Reserved for widespread rot, fire or water damage, or panels too thin for the framing.
Choosing material and thickness
For spot replacement, match the existing thickness, typically 7/16 inch OSB or 1/2 inch plywood on homes with 24 inch rafter or truss spacing, with H-clips at unsupported panel edges. For a full redeck, plywood handles brief wetting better, while OSB is uniform and less expensive. Thicker 5/8 inch panels make a stiffer, flatter roof and hold nails better, which is worth considering on wider spans. See OSB vs plywood roof decking.
Protect yourself on price
No one can see the full deck until the shingles are off. A good contract states a per-sheet replacement price in advance, and the crew should show you photos of bad wood before charging for it. If the reroof is an insurance claim, deck damage from the covered loss can be added through a supplement. See what to expect on roof replacement day.