ripples and waves on my new roof

Old 02-06-10, 05:50 PM
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ripples and waves on my new roof

In Dec, I found leaks from the north half of my roof. I ordered the new roof for the whole thing, but only stripped that leaky part down. It was ship lap under the felt, so I put down 3/8 OSB to smooth it out. Then I laid my metal edge, and the felt, and the shingles on top. However, something is wrong. There are several sections where the shingles are not flat. There are sections, some as long as 10 feet, usually going from top to bottom pretty directly, but sometimes on a diagonal downward path, where the shingles look like they are on top of a roll in the roof. The risen sections are perhaps a foot wide, and as mentioned above up to 10 feet long. When I walk on those sections, I feel the section depress, as though it buckled underneath and now there is just air.... The rise is only an inch or so, but it looks horrible!
I laid that part in December, it was just above freezing through the days, but I had to sweep the frost off every morning. I tried to ensure the underlayment was flat, but there may have been some SLIGHT bubbles. Not like what I am seeing now though. I put nails into the new 3/8 OSB every 18 inches or two feet. Each shingle was nailed down as per direction on the product. What the heck went wrong??
Old 02-08-10, 03:36 PM
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My guess it that some moisture was trapped under there. If you post some pics to
someone may be able to give you a better answer.
Old 02-08-10, 05:17 PM
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Not enough nails in OSB to hold it flat.
Old 03-05-10, 07:17 PM
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Did you properly space the OSB while installing it? Typically OSB and other types of plywood call for 1/8" spacing to allow for expansion. Also you probably should have used screws because if you used a smooth shank nail it could have already started pulling up.

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