Our roof looks wavy. For three months there was a delay, so they never finished the smaller part of the roof and left the stacked shingles on the roof for three months. Did the weight of the shingles warp the roof???
Very good chance is was from the weight sitting on the sheathing area that was in between the trusses .
Weight on that area for a short time wouldn't be a problem , but for three months it would be.
The wood sheathing will get soft after it rains ,
And if all that weight sits on the sheathing between studs (trusses) the sheathing will warp.
To repair it the sheathing will need to be replaced in the bad area
It could very have caused the strand board sheeting to deflect and stay that sway after the weight was removed but looking at the pictures, it looks more high in the one spot than low. This can happen when the starter membrane is installed too loose or the shingles are installed too tight. If you can step on the high spot and it flattens out than the answer is in the membrane/shingles and not the sheeting.
It is more likely that the leading edge shingle or a regular shingle near the bottom row were nailed too tightly which would cause for the lift in the middle of the shingle.
A roofer should be able to get in there and replace a few shingles to complete the proper install. As someone else already mentioned - if you can step on that area and it goes flat, then it is just the shingle that is out of place.
Its seems like there might be an piece of roofing that might be causing this wave. I cannot say from pictures if the structure was altered by the weight of the shingles stack left there for 3 months. I can be reached at 5068742339 for further questions.
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