Homeowner guide · Roofing
Do I need new plywood when I replace my roof?
Usually, sound plywood can stay. When the old shingles come off, your roofer checks whether the wood underneath is solid, can hold the roofing nails, and is suitable for the new shingles. Damage in one area may call for a local repair. A whole new deck needs its own explanation.
From a Bremerton roof replacement
One opening. A repair you can see.
On this home, John found a section of decking that had given way. These two photos show the same part of the job at the moment a homeowner would want to see it: after tear-off and again before the repair was covered.
What is the roofer checking?
The deck, also called sheathing, is the layer of wood fastened to the roof framing. It gives the underlayment and shingles a solid surface. You may hear someone call the whole thing “plywood” even if your home has oriented strand board (OSB) or older wood boards.
- Wood that can stay
- A solid, adequately supported deck that holds fasteners and meets the new shingle system’s requirements can generally be reused. A dark mark may prompt a closer look. Color alone tells you little about the wood’s strength.
- A section that needs repair
- An opening like the one in John’s photo is easy to see. Other damage is less obvious: a panel may be soft, broken, or separating into layers. Ask the roofer to show where the damaged area ends and how the replacement will be supported.
- When the recommendation covers the whole roof
- Damage may be widespread, or the existing boards may have gaps that make them unsuitable for the chosen shingles. Ask whether the proposal calls for removing damaged wood or adding a continuous layer over sound boards. Those are different scopes of work.
Can John tell before the shingles come off?
An inspection can reveal clues, especially where the underside of the deck is visible from the attic. The shingles and underlayment still hide the top face. A roofer may be able to flag a concern before quoting and only determine its full extent during tear-off.
That uncertainty belongs in the written proposal. Look for how much decking work is included, how additional work is measured, and who gives approval. See what belongs in a roof proposal.
Three questions to ask before you approve new plywood
- “Can you show me where the wood has failed?” Ask for a close-up and a wider photo that locates the spot on your roof.
- “How much needs replacing, and why?” Ask which sections can stay and what the repair includes. If the recommendation is for the entire deck, ask what condition or installation requirement applies across the roof.
- “What does this change in my proposal?” Ask for the quantity, the installed price for the additional work, and the revised total in writing before you approve it.
Have a question about your roof deck?
If a proposal mentions sheathing or you’re worried about a soft spot, tell John what prompted the question. He offers a free initial roof inspection in Tacoma, Lakewood, Bremerton and the surrounding service area.
Technical reference: Asphalt Roofing Manufacturers Association guidance on reroofing and deck condition (PDF).