Is it ok to install OSB over plywood roof decking?
Adding OSB over existing plywood provides a better surface for shingles to hold onto. However, installing foil-backed OSB tightly against plywood fails to insulate the house because the foil must face open air in the attic to work. Instead, this double-layered installation risks trapping moisture between the wood.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1hoping the shingles are installed tightly to prevent moisture entryDid this help you?
- 2relying on attic ventilation through soffit and ridgeDid this help you?
- 3install the roof immediately over the wet decking to prevent further soakingDid this help you?
- 4leave the decking exposed to the rain and wait for a prolonged dry spell to resume workDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Yeah that's kind of what im concerned about. The installation looks clean. I guess I'll just hope the shingles are installed really tight so no moisture gets in”source ↗
“I was talked into adding OSB onto the plywood, which my understanding is would create a better surface for the shingles to hold onto.”source ↗
“They also said it would insulate my house, which im reading is inacurate since the foil side of the osb would have to be facing open air in the attic to have an effect like that, and that in fact, foil facing plywood, how its installed, may trap moisture.”source ↗
“Is it ok that osb was installed over my plywood ?”source ↗
“Should we let the decking get rained on for the next 10 days and then let it dry out for a few days and start the roofing process after a few sunny days or go ahead and put the roof on with wet decking before the long stretch of rain?”source ↗
Where this came up
People with this problem also raised
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- 2Why is my house so hot after getting a new roof?
- 4Why is there condensation and damp spots on walls only on laundry days?
- 19How to temporarily waterproof a damaged roof until replacement
- 4Can I install siding, soffit, and fascia before roof shingles?