Replacing rotten roof decking costs $75 to $150 per 4 × 8 sheet installed. OSB sheets run $70–$150 and plywood $90–$175. Replacing the entire deck adds $2–$5 per square foot of roof, typically $4,000–$10,000 on an average-sized house. On a sound roof, a re-roof often needs only a few sheets, which adds a few hundred dollars.
Below: prices by type of decking, what a few sheets and a full redeck cost on a real roof, where rot is usually found, and the contract wording that keeps the change order fair.
Installed prices for 2026, not a quote. Sources are listed at the end.
Price by type of decking
| Decking | Replacement cost, installed | Per ft² |
|---|---|---|
| OSB, 4 × 8 sheet | $70–$150 per sheet | $2.19–$4.69 |
| Plywood, 4 × 8 sheet | $90–$175 per sheet | $2.81–$5.47 |
| Plank or board decking | $50–$150 per plank | — |
| Full redeck, any sheet goods | $2–$5 per ft² of roof | $2–$5 |
A 4 × 8 sheet covers 32 ft², so the per-sheet price divided by 32 gives the per-square-foot rate. Most contracts replace like with like: plywood where the house has plywood, OSB where it has OSB, and matching thickness so the new sheet does not leave a step under the shingles.
What it adds to a real roof
On the 23.2-square roof used across this site (2,320 ft² of roof, typical re-roof price $12,992):
| Situation | Sheets | Added cost | Share of typical re-roof |
|---|---|---|---|
| A few soft spots | 3 | $225–$450 | about 2–4% |
| Leaks at eaves and a valley | 8 | $600–$1,200 | about 5–9% |
| Full redeck | about 73 | $4,640–$11,600 | about 36–89% |
A few sheets rarely change the decision to re-roof. A full redeck can add more than half the price of the roof, which is when it becomes worth comparing against the repair or replace tests, or pricing a longer-lasting material that would make the deck work a one-time cost.
Why decking is priced as a rate
The deck is under the shingles and underlayment. Nobody, including an honest contractor, can count bad sheets from the ground or from the attic with certainty. So contracts price decking as a unit rate applied after tear-off, not as a fixed amount.
A change-order sheet often costs more than the per-sheet average inside a full redeck. Replacing eight scattered sheets means stopping the crew eight times; replacing the whole deck is one continuous task.
Where rot is usually found
Rot follows water, so it clusters in predictable places:
- Around chimneys, vent pipes and skylights, where flashing has leaked.
- Along the eaves, where ice dams back water under the shingles in cold climates. Eave membrane rules are in ice and water shield requirements.
- Under valleys, where two planes send their water into one line.
- Under a second layer of shingles, where moisture has been trapped. See tear-off vs roofing over.
Signs visible before tear-off: a sag between rafters, a soft feel underfoot, stains on the underside of the deck in the attic, or daylight through it.
When the whole deck is replaced
A full redeck is typical on:
- Houses with long-standing leaks across several areas
- Old plank decking with gaps too wide for modern shingle nailing
- Roofs where the existing sheathing is thinner than the shingle manufacturer or local code requires
The contract wording that matters
Three items decide whether a decking change order is fair:
1. An included allowance. "Price includes replacement of up to 3 sheets" means the rate applies only beyond that point.
2. A stated unit rate. "$95 per 4 × 8 OSB sheet, installed" can be checked against the $70–$150 range. "Decking replaced as needed" with no rate leaves the final price open.
3. Proof. Ask at signing for photos of each damaged sheet in place before it is removed. It takes the crew seconds per sheet and removes most disputes.
Two quotes with the same total are not equal if only one states an allowance and a per-sheet rate. How to compare the rest of a quote is in roof replacement cost per square.
Labor for decking
Published prices for decking are almost always quoted installed, with labor included, because the work happens in the middle of a tear-off by the same crew. Labor for the whole roof, including how pitch and stories change it, is covered in labor cost to install shingles.
The short version
- Budget $75–$150 per 4 × 8 sheet installed; plywood costs more than OSB.
- Expect a few sheets on a roof with no known leaks: a few hundred dollars.
- A full redeck adds $2–$5 per ft², or $4,640–$11,600 on a 23.2-square roof.
- Get an included allowance, a per-sheet rate and photos written into the contract.
Where these numbers come from
- $75–$150 per sheet: SquareDash, roof repair cost, updated April 9, 2026.
- OSB $70–$150 and plywood $90–$175 per sheet installed, planks $50–$150, full redeck $2–$5 per ft² and $4,000–$10,000 on an average home: Roof Medic, roof sheathing, updated June 23, 2026.
- Typical re-roof cost of $12,992 for 23.2 squares: the price basis used across this site; see roof replacement cost.
- Sheet counts and shares: calculated from 32 ft² per sheet; the 3- and 8-sheet cases are illustrative.