CSLB C-39 Roofing ContractorSafety and RepairMedium
A roofing crew is performing a tear-off on a residential roof in California. They encounter a section of the roof deck that has been severely compromised by dry rot, affecting approximately 20 square feet. The existing sheathing is 1/2-inch plywood. What is the correct procedure for repairing this dry rot damage before installing the new roofing system?
- ACut out the compromised sheathing to the nearest sound framing members and replace it with new, matching plywood.
- BFill the rotted areas with a wood filler compound and then sand smooth before installing the underlayment.
- CApply a fungicidal treatment to the dry rot and then cover it with a new layer of plywood.
- DReinforce the damaged area with metal strapping and then proceed with the new roof installation.
Show answer & explanationAnswer & explanation
Correct answer: A. Cut out the compromised sheathing to the nearest sound framing members and replace it with new, matching plywood.
Dry rot significantly weakens the structural integrity of the roof deck. To properly repair it, the compromised material must be completely removed to the nearest sound framing members and replaced with new sheathing of the same thickness and type to maintain structural continuity and support for the new roofing system.
Why the other options are wrong
- B. Wood filler compounds are not suitable for structural repairs of dry-rotted sheathing.
- C. Fungicidal treatment alone is insufficient for structurally compromised dry rot; replacement is necessary.
- D. Metal strapping does not address the underlying structural weakness caused by dry rot.
Dry Rot Sheathing Repair
The process of removing and replacing roof sheathing damaged by dry rot to restore structural integrity.
- Dry rot weakens wood.
- Compromised material must be fully removed.
- Replaced with matching new material.
Memory trick: Rotten wood? Cut it out, new wood rout!