Greetings! Long time lurker. Part time carpenter when I’m not teaching at a local trade school. My wife and I are building a house with a mono slope roof in mid coast Maine . We went with TJIs for rafters, 8 inches closed cell spray foam and capped with Zip sheathing, underpayment and owens Corning shingles.

I trust our roofer (he’s done dozens of jobs for the crew I work with) and we have a real head scratcher on our hands. All of the drip edge is cupping off the roof at each of the seams (they are overlapped, not butted.) See pictures below.

The roof was put on at the end of November but it wasn’t terribly cold that day. About 50 degrees. That makes me think that thermal expansion isn’t a crazy huge issue but I can’t think of any other reason for this to happen. The rest of the roof looks fine except for one spot where the shingles were a little tight. (Forgiveable and has been fixed.)

My current thinking is that there is a much larger temperature swing on the eaves of the roof (16” overhangs) and so it’s going though much larger heat cycles. But that is a shot in the dark. Any other thoughts are greatly appreciated. The roofer really wants to make it right but without understanding the cause it’s hard to follow through on that.

Note: that one piece of shadow board that has a curve hasn’t always been that way. Cedar has been tough to come by lately and that piece was more curved as could be.)