CSLB C-39 Roofing ContractorSafety and RepairHard
A contractor is performing a reroof of a residential building in an area prone to high winds. The existing roof deck is comprised of skip sheathing. What specific California Building Code (CBC) requirement related to roof sheathing must be addressed during this reroofing project?
- AA minimum 1/2-inch plywood or OSB overlay must be installed over the skip sheathing.
- BNew roofing materials must be mechanically fastened through the skip sheathing directly into rafters.
- COnly lightweight roofing materials are permitted over existing skip sheathing.
- DAll skip sheathing must be removed and replaced with solid sheathing for any new roof covering.
Show answer & explanationAnswer & explanation
Correct answer: A. A minimum 1/2-inch plywood or OSB overlay must be installed over the skip sheathing.
The CBC (and generally good practice) requires a continuous, solid substrate for most modern roofing materials. For existing skip sheathing, this means installing an overlay of at least 1/2-inch plywood or OSB to provide a proper fastening surface and structural integrity.
Why the other options are wrong
- B. Nailing directly into rafters through skip sheathing is generally insufficient for proper fastening and wind resistance of modern roofing, which requires a continuous substrate.
- C. This is incorrect; the type of roofing material is less relevant than ensuring a solid, continuous deck for proper fastening and structural support, which an overlay provides.
- D. While replacing with solid sheathing is an option, an overlay is often permitted and more cost-effective if the skip sheathing is otherwise sound.
Skip Sheathing Reroofing
When reroofing over existing skip sheathing, the California Building Code requires an overlay of at least 1/2-inch plywood or OSB to create a solid substrate.
- Skip sheathing is not suitable for most modern roofing.
- Overlay provides continuous fastening surface.
- Ensures structural integrity and wind resistance.
Memory trick: Skip sheathing needs a solid cover, for the new roof to forever hover.