Does anyone have an idea why this happens? We had a new asphalt shingle roof put on about 5 years ago. The chimney lead flashing was replaced with new, and when all done, it was lying flat on the shingles as it should be.
About 4 months ago I noticed that one of the corners of the lead had curled up enough that wind-driven water might have been able to get into the house, so I went up on a step ladder and reached up with a very long snow roof rake to squash it back down flat. Worked easily. Now, i see that it is slightly curled up again, lifted perhaps an inch at this point.
Does anyone know what the mechanism is that is causing the lead flashing to curl up on that one corner?
Thanks.
emichael