Rotten Decking Found During a Roof Replacement: What It Means and Who Pays
Nobody can see the roof deck until the old shingles are off. Here is why rot gets discovered mid-job, who normally pays, and the one contract line that removes the surprise.
Quick Answer: The 90-Second Summary
- Decking (the plywood or OSB sheets under the shingles) can only be fully judged once the old roof is torn off. Estimates normally cover the work on the surface and treat damaged decking as a separate, priced item.
- In most residential contracts the homeowner pays for replacing deck sheets found to be rotted, delaminated or otherwise unfit to hold fasteners, unless the contract says otherwise or an insurance claim covers the cause.
- The fix for the surprise is simple: get a per-sheet price in writing before work starts.
You signed an estimate, the crew tore off the old shingles, and now you get a call: some of the plywood underneath is bad. It's one of the most common and most stressful moments in a roof replacement, and it feels worse when no one explained it first. Here is what's actually going on.
What is roof decking?
Decking, also called sheathing, is the layer of plywood, OSB (oriented strand board) or, on some older homes, plank boards nailed to the rafters. Shingles are nailed to it. A standard sheet is 4 by 8 feet, or 32 square feet. Underlayment sits on top of the decking, and the shingles sit on top of that. If the deck is soft, swollen or crumbling, new shingles can't be fastened securely.
Why can't anyone tell before the tear-off?
Because the evidence is under the shingles. From the attic, a roofer can see some of it, such as stains, dark patches and sagging. From the outside, a roofer can feel for soft spots while walking the roof. But a roof inspection can't confirm the condition of every sheet. The reliable answer comes only when the old roofing is off and the whole deck is visible. This is why a good contractor explains decking policy before the contract is signed, rather than after.
What does bad decking look like?
- Dark staining or discoloration on the underside or top of the sheets
- Soft, spongy or crumbling spots that give underfoot or break apart
- Delamination, where plywood layers peel apart, or OSB swells and flakes at the edges
- Sagging between rafters
- Rot or fungal growth, often near leaks, vents and valleys
- Nails that don't hold, or fasteners that are rusted through
- Water stains and mold visible from the attic
- Gaps or damage along old plank decking
What usually causes it?
- A long-running leak at flashing, a pipe boot, a chimney or a valley
- Condensation from poor attic ventilation or humid air leaking into the attic
- Ice dam backup at the eaves
- A bath fan or dryer vented into the attic
- Old age, multiple shingle layers and repeated wetting
If the damage came from a sudden covered event such as a storm, ask your insurer whether any of it falls under your claim. Long-term seepage or wear is typically treated differently by policies.
Who pays?
| Situation | Who typically pays | Why |
|---|---|---|
| The contract lists a per-sheet price for replacing bad decking | The homeowner pays the listed price for each sheet replaced | The price and the trigger were agreed in advance |
| The contract says "decking extra" with no price | The homeowner, at a price negotiated after the surprise | This is where disputes begin |
| The contract includes a fixed allowance or a stated amount of decking | The contract's terms apply | Read the allowance and what happens when it is exceeded |
| Damage resulting from a covered storm, with an open insurance claim | The insurer, under the policy's terms | Coverage depends on the cause and the policy |
| The contractor's own error damaged sound decking | The contractor | That is a workmanship issue |
The line that prevents the surprise
Before you sign, ask for a decking clause that covers:
- A per-sheet price for replacing damaged 4 by 8 sheets, including materials and labor
- How the price changes for plank decking, special cuts or work at the eaves and valleys
- Who decides what is bad, and how it is shown to you
- How you'll be notified, and whether work stops for your approval before extra sheets are replaced
- A written change order for any decking work beyond the base contract
- Counting and photo proof, so each replaced sheet is documented
What a good decking process looks like
When the tear-off reveals damage, a good crew should:
- Photograph the damage before and after replacement, with the location noted on a roof sketch
- Mark the sheets that need replacement
- Call you with the number of sheets and the price per the contract, before proceeding when the contract requires it
- Replace to a consistent standard, securely fastened to the framing
- Give you the final count with photos in the closeout paperwork
If the damage is extensive, or if framing such as rafters or trusses is affected, the work may need more than sheet replacement, and a permit may be involved. See our guide to Fairfax City and County roofing permits.
Why some quotes are lower than others
A quote that leaves out decking, or says only "if needed," can look cheaper than one that states a price per sheet. It isn't necessarily better. When you compare estimates, compare the decking terms along with the shingles, flashing and ventilation.
Fix the cause, not only the sheet
If rot is found, ask what caused it. Replacing wet decking without fixing a leak, a ventilation problem or a bath fan venting into the attic invites the same problem again. For more, see our guide on telling attic condensation from a roof leak.
"If you find rotten decking, how much per sheet, who decides it's bad, and will you call me before you replace it?" The answer tells you how the rest of the job will be handled.
Frequently Asked Questions
Why wasn't the bad decking in my original estimate?
It can't be fully seen until the old roof is removed. Good estimates state a per-sheet price for replacement so the cost is known in advance even if the number of sheets isn't.
Is rotten decking covered by homeowners insurance?
It depends on the cause. Damage from a sudden covered event may be covered, while long-term leaks, rot and wear are typically treated differently. Check your policy and ask your insurer.
How many sheets of decking usually need replacing?
There is no reliable typical number. It depends on the roof's age, leaks, ventilation and moisture history. That is why the per-sheet price matters more than a guess.
Can I refuse to replace the decking?
Soft or rotted decking can't hold fasteners well, and installing new shingles over it can compromise the roof and the warranty. Ask your contractor to show you the damage and explain the options.
What if the decking is plank boards instead of plywood?
Older plank decking can be repaired or replaced, and some roofers recommend overlaying it with sheet material. Ask your roofer how that is priced and handled.
Get a Roof Estimate with Decking Priced Per Sheet
We inspect the roof and attic first, then put the decking policy and per-sheet price in your written estimate so there are no surprises after the tear-off. Call (571) 294-4977.
Request an Itemized Estimate