Why is the plywood roof decking sagging on my new house?
Premature sagging and warping on new roof decking is typically caused by trapped moisture due to poor attic ventilation. This excessive humidity compromises the structural integrity of the plywood, leading to noticeable dips between the roof rafters.
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.
- 1contacting the contractor's licensing board to enforce a judgmentDid this help you?
- 2putting solar panels on to hide the damageDid this help you?
- 3ripping off and replacing the roof sheathingDid this help you?
- 4Withholding final payment until the issue is fixedDid this help you?
- 5Leaving the sag alone to avoid potential problems and leaks from tearing up new shingles and underlaymentDid 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.
“The attic is poorly ventilated. The moisture has affected the plywood decking causing it to sag.”source ↗
“It's definitely not a good sign that it looks like that. It's indicative of issues with the roof deck.”source ↗
“Insurance covered my roof replacement and the sheet that they put shingles over was definitely torn up pretty good and should have been replaced, imo. There’s a clear dip in this section of the roof.”source ↗
“I've got the same situation. Before I bought my house, someone put a foot through a rotted section of roof. They just replaced the majority of the rotted section. They didn't put any hclips, and the new piece sagged. 11 years later, this year actually, we paid for a new roof. I specifically told the roofer to replace the sag. He forgot.”source ↗
Where this came up
People with this problem also raised
- 2Why is my new roof bulging?
- 2Rotted roof decking and mold around chimney
- 11Do I need a structural engineer for a sagging floor beam?
- 5Is a gap in roof sheathing at the ridge okay before shingling?
- 5Why is my new house roof made with cheap materials and visible beams?
- 11How to fix cement fiber siding touching roof shingles