Definition
What is roof decking and rafter repair?
Roof decking and rafter repair replaces rotted or damaged sheathing and strengthens or replaces damaged framing so the roof has a solid base again.
Decking is the layer of plywood or OSB sheathing nailed to the rafters or trusses. Shingles and underlayment are fastened to it, so if it softens, nails lose their grip and the roof surface above starts to fail. Rafters and truss members carry the weight of the roof; if they're damaged, the roofline can sag.
This work usually follows a leak that went on for a while, or a storm that broke through. It's one of the less common roof leak fixes for Cibolo homes, but one of the most important, because new shingles on rotten decking won't hold. Many homeowners find out about it when a roofer lifts shingles for a routine repair and finds soft wood underneath, which is exactly the right time to fix it.
Methods
How are rotted decking and rafters repaired?
Repairs are sized to the damage, from a single sheet of decking to reinforcing framing.
- Locating the damage. The roofer checks from the attic for dark, soft or delaminated sheathing and from the roof for soft spots underfoot.
- Removing roofing above it. Shingles and underlayment over the damaged area are removed.
- Cutting out bad decking. Damaged sheathing is cut back to solid wood, with new edges landing on rafters or with added blocking.
- Installing new sheathing. New panels matching the existing thickness are fastened with the correct spacing and nailing pattern.
- Framing repairs. Damaged rafters are sistered with new lumber fastened alongside, or replaced where needed. Truss damage may require guidance from the truss manufacturer or an engineer.
- Re-roofing the area. New underlayment, flashing and shingles are installed and tied into the surrounding roof.
Where the leak came from matters too. There's no point replacing rotten wood if the original flashing or pipe boot is still failing. The source repair and the structural repair should happen together, and a good provider will show you both before any wood is replaced. Photos of the damaged wood before it's covered are worth asking for, since the finished roof hides everything underneath.
Edges and eaves get special attention. Decking along the eave often softens first because overflowing gutters and heavy runoff hit it repeatedly. Fascia and the tails of the rafters behind it can be affected too, and a thorough repair checks all three before the new roofing goes on.
Warning signs
8 signs of damaged decking or rafters
Some of these you'll see from inside the attic. Others show up on the roof itself.
- A dip or sag in the rooflineDecking or framing has weakened.
- Soft or spongy spots on the roofDecking underneath is rotted.
- Dark, delaminating sheathing in the atticWood has been wet repeatedly.
- Daylight through the deckingHoles or gaps have formed.
- Rusty nails and water tracks on raftersLong-term leaking along the framing.
- Cracked or split raftersFraming is damaged or overloaded.
- Shingles that won't stay nailedFasteners can't grip soft wood.
- Mold or fungus on attic woodMoisture has been present long enough to cause decay.
Causes
What damages roof decking and rafters?
Wood roof structures fail for predictable reasons, and most of them involve water.
- Long-term leaks. A slow drip from a pipe boot or flashing can soak the same spot for months.
- Attic moisture. Condensation from poor ventilation keeps decking damp over large areas.
- Gutter backup at the eaves. Overflow soaks the edge of the decking and fascia; see gutter and drainage repair.
- Storm impact. Falling limbs can crack decking and rafters directly.
- Extra weight. Equipment added to the roof without support can overload framing.
- Previous poor repairs. Layered patches that trap water accelerate rot.
OSB sheathing in particular tends to swell and lose strength when it stays wet, which is why early leak repair protects more than just the ceiling. Plywood holds up somewhat better but still delaminates after repeated soaking.
Sagging isn't always rot. Rafters that were undersized, cut to fit new equipment, or overloaded by a second layer of shingles can bow over time. An experienced provider can tell the difference, and will say plainly when a question needs an engineer's opinion rather than a roofer's.
Safe checks first
What can you check from the attic?
An attic check with a flashlight is the safest way to spot structural problems.
- Walk only on the framing, never between joists, and bring a strong flashlight.
- Look at the underside of the decking for dark, swollen or flaking areas, especially around vent pipes and at the eaves.
- Check rafters for water tracks, cracks and splits.
- From outside, look along the roofline from the street for dips or waves.
- Note any spots where daylight shows through, and photograph what you find.
Pay special attention to the areas around plumbing vents, chimneys and skylights, and along the lower edge of each slope. Those are where water enters most often, so they're where rot starts. Dark wood that's dry today can still be weak, since the damage stays after the leak stops.
If you're not comfortable in the attic, a roofer can do the check. Share any photos you've taken and the history of past leaks, which helps them know where to look first.
Press gently on stained decking from the attic with a screwdriver handle. Solid wood resists. Wood that feels soft or crumbles means it needs replacing, not just drying.
The pro visit
What happens during a structural roof repair?
Structural repairs follow a careful sequence.
Inspection from above and below
The provider checks the attic and roof to map the damaged area.
Find and fix the source
The leak causing the damage is identified so it's repaired at the same time.
Remove roofing and bad wood
Shingles and underlayment come off, and rotted decking is cut out.
Repair framing
Damaged rafters are sistered with new lumber or replaced as needed, and you're shown the work before it's covered.
Install new decking
New sheathing matching the existing thickness is fastened to solid framing with the correct nail spacing.
Re-roof and inspect
Underlayment, flashing and shingles are installed and tied into the existing roof.
Cost factors
What affects the cost of decking and rafter repair?
Structural repair pricing comes from the provider after an inspection. These factors drive it most.
| Factor | Keeps cost lower | Pushes cost higher |
|---|---|---|
| Area of damage | One or two sheets of decking | Large section across a slope |
| Framing involvement | Decking only | Sistered or replaced rafters or truss repairs |
| Roofing to remove | Single layer of shingles | Multiple layers or specialty roofing |
| Access | Low pitch, open attic | Steep roof or tight attic |
Urgency
When is structural roof damage an emergency?
Structural roof damage is an emergency when the roof or ceiling is visibly sagging, when you hear cracking, when a limb has broken through, or when a large soft area appears after a storm. Keep people out of rooms under the sagging area.
If there's an opening in the roof, get it covered with emergency roof tarping while the structural repair is planned.
Never walk on a roof that feels soft or sagging. Weakened decking can give way underfoot.
Questions
Roof Decking & Rafter Repair questions from Cibolo homeowners
How do I know if my roof decking is rotten?
Soft spots on the roof, dark or delaminating wood in the attic, and shingles that won't hold nails are common signs.
Can rotten decking be repaired without a new roof?
Yes. Damaged sections can be cut out and replaced, then re-roofed and tied into the existing shingles.
What does sistering a rafter mean?
It means fastening new lumber alongside a damaged rafter to restore its strength without removing the original.
Can trusses be repaired?
Often, but truss repairs may need guidance from the manufacturer or an engineer. Ask the provider how they handle it.
Should decking be replaced during a re-roof?
Damaged sections should be. A good provider checks the decking once shingles are off and replaces what's soft.
How long does decking repair take?
Small repairs can be done alongside a standard repair visit. Larger areas or framing work take longer.