Roof Sheathing Lifting After Roof Replacement
About two months ago I had a complete tear-off and roof replacement on my 1963 Cape Cod style home. This included replacing eighteen 4 X 8 sheets of plywood, due to what I believe is 45 years or so of moisture from the inside of the house breaking the plywood down. The wood replacement was on the north side of the roof only. All other roof areas had good wood. Shingles were Certainteed AR 25 (year warranty).
About a week after the roof was installed I noticed slight "bulging" on the surface of the roof in various places, only on the portion where the plywood was replaced. I figured I would give it a couple of months for the shingles to lay flat and then take a close look, but the bulging got a little worse.
I examined it closely yesterday. The plywood that was replaced is bowing, or bulging, lifting up the shingles in a few places. You could see it plainly at the edges of the roof. The bulge is about half an inch to an inch high and covers about five feet or so and is in several places across the roof.
I watched the roofers closely when they worked. The plywood is exterior grade, but no plywood clips were used to provide a gap between adjoining pieces, where installed. The plywood was installed without any gap (I think the shingle package stated to have a small gap).
I think the plywood must have expanded and lifted, or that it was not properly fastened -- perhaps only the corners were nailed down and its lifting in the middle.
I think the only proper fix is to tear off the roof and start over and correctly replace the wood on the north side. I plan to have the roofer come by and offer his explanation, but imagine he will tell me "Its OK, don't worry about it, it will be fine".
Is this a big problem that could shorten the life or compromise the roof, or just a slight cosmetic issue? Is the roofer at fault, or is this an unavoidable bowing or a defect in the plywood? I have never noticed this problem on any other roof I have seen installed. Opinions?