Roof decking rot is wood sheathing under your shingles that has soaked up moisture long enough to go soft, crumble or lose its grip on nails. The fix is two steps in a fixed order: find and stop the moisture source, then cut out and replace the damaged panels. Skip the first step and the new decking will likely rot again. This guide shows you how to recognize rotted roof sheathing, what causes it, when replacement is the right call, whether insurance may help, and what to do this week.
TL;DR
- Rotted decking feels soft or spongy, sags, crumbles, or smells musty. It usually starts at a leak or from attic condensation.
- Replace the rotted panels after the moisture source is fixed. A small spot that got wet briefly may not need replacement.
- Insurance generally does not pay for rot that comes from poor maintenance. It may pay when a covered event such as wind or hail opened the roof.
- Decking is often priced per sheet, and the full extent of damage is often confirmed only at tear-off, so ask for the per-sheet price in writing.
- Get a roof inspection now if you see sagging, stains or a musty attic. Waiting turns a patch into a larger repair.
Table of Contents
- What roof decking is and why rot matters
- What causes roof decking to rot
- How to tell if roof sheathing is rotted
- When to check your roof decking
- When to replace roof decking
- How rotted decking is replaced
- What roof decking replacement costs
- Will insurance cover roof rot?
- How to keep decking from rotting again
- Our perspective
- Get your roof deck checked in Central Texas
- Your next steps
- FAQ
- Sources
What roof decking is and why rot matters
Roof decking, also called sheathing, is the layer of wood panels, usually plywood or OSB, nailed over your rafters or trusses. Your underlayment and shingles are fastened to it. GAF describes it as a thin sheet of wood between the shingles and the rest of the house.
That thin layer carries a lot of work. It holds the roofing in place, ties the roof framing together and gives roofers a safe surface to walk on. When it rots, nails lose their grip, shingles loosen, and the roof can sag. A person stepping onto a rotted area can break through.
In Central Texas, the roof takes hail, wind-driven rain, long stretches of heat and the occasional hard freeze. A shingle that is cracked, lifted or missing a nail seal lets water reach the wood. Once the wood stays wet, rot is a matter of time.
What causes roof decking to rot
Almost every case traces back to one of two sources: water coming in from outside, or moisture building up from inside the house.
Leaks from the roof surface
GAF says the most common cause is moisture from a roof leak or attic condensation. Leaks tend to start at the same weak points:
- Flashing around chimneys, skylights and plumbing vents
- Roof valleys and edges
- Exposed or backed-out nails (see our guide to nail pop patterns and how to vet estimates)
- Cracked, curled or missing shingles after storms
- Clogged gutters that push water back under the roof edge
Wind and hail are the big triggers here. If a storm lifted shingles or bruised the roof, the damage can sit unseen for months. Our pages on wind damage to a roof and the steps to take after hail damage cover what to look for.
Condensation and air leaks from inside
Not every rotted deck comes from a leak. The U.S. Department of Energy's Building America research lists interior air leakage, vapor diffusion, inadequate drying and condensation as ways sheathing moisture can climb and lead to mold or decay. Humid indoor air that reaches a cold underside of the deck can condense, even with a perfectly sealed roof surface.
Common household culprits include bathroom or kitchen exhaust fans that dump into the attic instead of outside, gaps around attic hatches and light fixtures, and poor attic ventilation. A roofer who only replaces the wood and shingles will miss these. That is why a good inspection looks at the attic as well as the roof.
How to tell if roof sheathing is rotted
GAF lists these signs of rot: a soft or spongy texture, sagging, cracking or crumbling, discoloration, growths or powder, and a musty odor. Here is where you will notice each one.
| What you notice | Where | What it may mean |
|---|---|---|
| Soft or bouncy feel underfoot | Roof surface (do not walk on a suspect roof) | Decking has lost strength |
| Sagging between rafters | Roofline from the street | Long-term moisture or failed framing support |
| Dark, damp or stained wood | Underside of the deck in the attic | Active or past leak |
| Crumbling, flaking or powdery wood | Attic, around vents and chimneys | Advanced decay |
| Musty smell | Attic or upper-floor ceilings | Trapped moisture, possible mold |
| Shingles that look wavy or lifted | Roof surface | Deck below may be swollen or soft |
| Ceiling stains | Upstairs ceilings | Water is getting past the deck |
A safe way to check
Stay off the roof. Wet or damaged decking can give way, and shingles are slippery. From the ground, look for sagging lines, wavy shingles and sunken spots with binoculars. From the attic, bring a flashlight and look at the underside of the deck. Dark patches, stains around nails, or wood that looks swollen are all worth a professional's time. Pressing a screwdriver gently into the wood from the attic side tells you a lot: solid wood resists, rotted wood gives.
We go deeper on what soft spots and moisture readings mean in our guide to roof decking soft spots.
When to check your roof decking
Sheathing should be looked at on a schedule and after certain events. IKO's guidance points to checking when buying or selling a home, after potential roof damage or moisture problems, during a full roof replacement, and before attic insulation or ventilation work. GAF recommends a professional roof inspection at least once a year and after storms.
In Central Texas, treat any hailstorm or high-wind event as a reason to inspect. Damage from a storm is easier to document and fix when it is fresh. Our storm damage roof inspection guide explains what photos to take and why we suggest collecting three bids.
When to replace roof decking
The short rule: replace wood that is rotted, and only after the cause is fixed. IKO's advice is that wood affected by dry or wet rot should be replaced once the moisture source is dealt with, while a small area that was exposed to water only briefly may not need replacement.
In practice, here is how most decisions go.
Replace the panel when
- The wood is soft, crumbling, delaminating or visibly dark and decayed
- Nails pull out easily or will not hold
- The deck sags or flexes under light pressure
- Mold or a persistent musty smell is tied to the wood
- The panel is water-soaked and has not dried out after the leak was fixed
A repair or monitoring may be enough when
- The wood is stained but firm, and it dried after a short exposure
- The affected area is small and the source of water is confirmed fixed
- A roofer has checked the area from both the attic and the roof surface
Why the roofer often cannot give a final number before tear-off
Decking hides beneath underlayment and shingles. A roofer can see attic stains and soft spots, but the full extent often shows only once the old roofing is removed. That is why a clear estimate states a per-sheet price for replacing bad decking and how each replaced area will be documented. If you are weighing a new layer over old roofing against a full strip, read our comparison of reroof versus tear-off. A rotted deck is one of the main reasons a tear-off is the safer choice, since you cannot repair what you cannot see.
How rotted decking is replaced
Here is the sequence a careful crew follows.
- Inspect and find the source. Check the roof surface, flashing, gutters, vents and the attic. Identify whether the water came from a leak, condensation or both.
- Strip the roofing. Remove shingles and underlayment over the affected area, or the whole roof on a replacement.
- Mark and cut out bad panels. Cut back to solid framing so the new panel has full support on the rafters.
- Check the framing. Look at the rafters or trusses under the rot. If they are damaged, they need repair before new decking goes on.
- Install new decking. Use panels of matching thickness, fastened to code with proper spacing.
- Fix the cause. Repair flashing, seal air leaks, redirect exhaust fans outside, and improve ventilation as needed.
- Reinstall underlayment and shingles. Roofing goes on only after the deck is sound and dry.
Building America's research makes the same point at a technical level: a roof assembly has to control both liquid water and the movement of vapor and air. Replacing wood alone does not do that.
What roof decking replacement costs
Most contractors price decking replacement per sheet on top of the main roofing job, because nobody can know exactly how many panels are bad until the roof is open. What moves the total:
- How many sheets are bad. A few panels near a leak is a small add-on. Widespread rot from condensation can mean much of the deck.
- Material. Plywood and OSB are priced differently, and thickness matters.
- Roof pitch and access. Steep or multi-story roofs take more labor and safety equipment.
- Framing repair. Damaged rafters or trusses add carpentry work.
- Fixing the source. New flashing, vent work or attic air sealing is separate from the wood itself.
- Tear-off timing. Replacing decking during a full re-roof is usually more efficient than opening the roof twice.
We do not publish set prices, because every roof is different. We give free estimates, and we state decking as a clear per-sheet line so you know what you would pay if the crew finds more rot than expected. When you compare bids, make sure each one says how bad decking will be handled. A low number that leaves the question open can become a bigger one mid-job.
Will insurance cover roof rot?
Usually not when rot comes from slow leaks, age or lack of upkeep. The Insurance Information Institute notes that homeowners insurance does not cover damage due to lack of maintenance. It also notes that policies vary, and that covered perils typically include windstorm or hail.
That leaves a middle path that matters in Texas. If a hailstorm or wind event damaged your shingles and that opening let water reach the deck, the storm damage and the resulting deck repair may fall within a claim. If the same deck simply rotted over years from an unfixed leak, the insurer may deny it. The details sit in your policy, so read it or call your agent before assuming either way. Our guide to roof exclusions in homeowners insurance explains the wording that most often trips people up.
Two practical tips if you think a storm is involved:
- Photograph the damage from the ground and the attic before anything is repaired or covered.
- Ask for an inspection report that ties the damage to the storm date, then file promptly. Policies often set deadlines for reporting.
How to keep decking from rotting again
Prevention comes down to keeping water out and letting the roof breathe.
- Inspect twice a year and after storms. GAF lists annual and post-storm inspections, gutter and downspout maintenance, debris removal and early attention to roof problems among the best protections.
- Keep gutters and downspouts clear so water does not back up under the roof edge. Fascia and soffit boards matter too, and we cover them in our guide to fascia and soffit repair.
- Ventilate the attic properly so warm, moist air has a way out.
- Vent exhaust fans outdoors, never into the attic.
- Seal air leaks around attic hatches, recessed lights and wiring openings.
- Fix small problems fast. A single lifted shingle is cheap to repair. A season of leaking through it is not.
Our perspective
Most homeowners call us about a stain on the ceiling or a spongy feel in the attic and ask how much a new roof will cost. The better question is where the water came from. Rotted decking is a message from the roof, and a repair that ignores the message is just a short delay.
We think the honest way to handle decking is to put it on paper before the job starts. That means a per-sheet price for any bad panels, photos of what we find at tear-off, and a plain explanation of the moisture source we fixed. Surprises on a roof job usually come from vague estimates, not from the wood itself.
We also tell homeowners to get more than one estimate. If our Best Price Guarantee is right for you, we will show it on paper, and if you have a storm claim, we will walk you through the insurance steps so you know what to document and what to ask.
Dan
Get your roof deck checked in Central Texas
If you see sagging, ceiling stains, a musty attic or soft spots, we can inspect the roof and the attic and tell you what is wrong, what caused it and what the fix involves. We handle repairs, full replacements, storm damage and insurance claim guidance for homes across Central Texas, with free estimates.
Start with our roofing repair and replacement services, or if a storm is involved, see how we make insurance claims easier. You can also browse past work in our roofing and siding gallery.
Your next steps
- Look, do not climb. Check for sagging and wavy shingles from the ground. Check the attic underside with a flashlight.
- Photograph everything with dates, especially after hail or wind.
- Stop the source. Cover obvious openings and clear gutters, but leave roof work to a professional.
- Get two or three written estimates that state the per-sheet decking price and how hidden damage will be handled.
- Check your policy and call your agent if a storm may be involved.
- Fix the cause with the wood. Ask each roofer how they will deal with ventilation, flashing and attic air leaks.
FAQ
How do I know if roof decking is rotted?
Look for sagging, soft or spongy spots, crumbling wood, dark stains, powdery growth and a musty smell. The attic is the safest place to check, since you can see the underside of the deck. Confirm with a roofer before deciding, because damage often hides under the shingles.
When should roof decking be replaced?
Replace it when the wood is soft, crumbling, delaminated or will not hold nails, and only after the source of moisture has been fixed. A small area that got wet briefly and dried firm may not need replacement. A roofer should check from both the roof and the attic.
Will insurance cover roof rot?
Typically not when rot is caused by poor maintenance or a long-ignored leak. If a covered event such as wind or hail damaged the roof and let water in, a claim may apply. Policies vary, so check your policy wording or ask your agent.
Is it expensive to replace roof decking?
It depends on how many sheets are bad and how hard the roof is to reach. Contractors usually price it per sheet on top of the roofing work, and doing it during a full re-roof is generally more efficient. Ask every bidder to put the per-sheet price in writing.
Can I just shingle over rotted decking?
No. Shingles need solid wood to hold nails, and covering rot hides a moisture problem that keeps spreading. Rotted panels should be cut out and replaced before new roofing goes on.
Sources
- Moisture-Safe Unvented Wood Roof Systems, U.S. Department of Energy Building America
- Roof Deck Wood Rot: How to Spot Damage, Prevent Decay and Replace Sheathing, GAF
- What is Wood Rot and When to Replace Roof Sheathing, IKO
- Which disasters are covered by homeowners insurance? Insurance Information Institute