When should you replace roof decking, and what does it cost?
Signs from the attic
- Dark stains or black areas on the underside of the sheathing, especially around chimneys, vents and valleys.
- Daylight showing at panel seams or nail holes.
- Mold or a musty smell near the roof deck.
- Sheets visibly sagging between rafters.
Signs from outside
- Dips or waves in the roof surface.
- Soft spots a roofer feels while walking the roof.
- Shingles that will not lie flat in one area.
How it is replaced
After tear-off, the crew walks and checks the deck. Bad sections are cut out along rafter centers and replaced with panels of the same thickness so the new roof lies flat, then nailed to the framing on the required schedule. The work adds little time to the job when it is a few sheets.
What it costs
Most contracts price decking per sheet, so the total depends on how many are bad. Ask for that price in writing before work starts, plus photos of each replaced area. A roof with widespread rot or old board decking that needs a full new layer costs more, and that should be explained before it happens.
Will insurance pay for it?
If decking was damaged by a covered event, such as a limb puncture, it is part of the claim. Rot from long-term leaks usually is not. Some code-required decking upgrades may fall under ordinance or law coverage; see code upgrade coverage. Panel types are compared in OSB vs plywood roof decking.