Does a New Roof Need New Decking?

Roof decking, also called sheathing, is the layer of wood boards or panels that sits on top of your rafters or trusses. Underlayment and shingles are fastened to it. IKO’s Cambridge shingle instructions (opens in a new tab), for example, say the deck must be smooth, firm, clean, dry, and securely nailed, with plywood panels at least 3/8 inch thick.

Decking is not the same thing as the framing that holds the shingles up. If a crew finds damage that goes past the decking into a rafter or truss, that is a structural repair. It is worth asking how it would be explained and priced.

Before the job, a contractor can look for warning signs such as soft spots, a history of leaks, or stains visible from the attic. These checks are helpful, but they are limited. Possible damage can be hidden under the shingles. Be sure to ask the contractor which areas they were able to check and which they could not.

The more accurate assessment occurs at tear-off. Remi’s timeline outlines that on the first day, the crew removes the old roofing, inspects the deck, and replaces any damaged sections before underlayment goes down.

Sometimes the issue is not damage at all. Some older homes have spaced boards with gaps between them instead of a solid deck, often left from an earlier cedar shake roof. Instead of swapping out a few rotted panels, the approach for this roof would be installing new sheathing. It is worth asking about early if your home once had a wood shake roof.

Because the amount of damaged decking is unknown until tear-off, many roofing bids include a small decking allowance or a per-sheet price for anything extra. The initial quote can look low, but the final bill depends on how much rotted wood turns up. When you compare bids, look for:

• How much decking, if any, is already included in the price
• What each additional sheet or square foot costs, and whether that covers labor and disposal
• Whether you approve extra decking before the crew installs it, and how that approval is recorded

In California, for example, the Contractors State License Board (opens in a new tab) says any change to the contract price or scope must be made with a written change order signed by you and the contractor before the change is made. Even where your state does not require it, getting extra work approved in writing gives you a clear record. Our roof estimate guide explains what a written estimate should say about conditions the crew can’t see until tear-off.

Remi’s guaranteed price takes the per-sheet question off the table. When your quote has a guaranteed price, replacement of any damaged or rotted decking is covered in the price you are quoted, so it does not show up later as a change order. The guarantee page puts the typical cost of replacing damaged decking at $2,400 to $8,600.

The guarantee has two exclusions. It doesn’t cover new structural decking where none exists, which Remi notes is very rare and typically happens only when asphalt shingles were laid over cedar shake with no decking. It also excludes elective fascia upgrades beyond code. Projects quoted under special discounts or promotions may not be eligible, so refer to your quote or ask your Remi team for details.

• California Contractors State License Board: Learn About Home Improvement Contracts (opens in a new tab) (checked 2026-10-25)
• IKO: Cambridge Shingles Application Instructions (opens in a new tab) (checked 2026-10-25)

Product instructions, warranty terms and local requirements can change; use the documents that apply to your project.

The Remi Editorial Team researches roofing materials, project planning and homeowner questions using manufacturer documents, public agencies and industry guidance. This article explains the decision; a contractor’s assessment and the written scope establish what your roof needs.