Our friends cottage has developed a leak in the shingle roof of the
screened porch part of their cottage. The leak isn't heavy, and is
less likely to occur during a rainstorm but rather at off rain times.
e.g. seems to happen each morning. The roof construction is un-
insulated/exposed in this portion of the house. I look up and saw a
16" wide x 6" patch of damp plywood sheathing centered on one of the
rafters.

The shingles are old but not curling. This is the only leak and it's
not a heavy one. One thing I noticed is that they get a heavy dew
build-up in the night time. I wasn't sure if that might be more
consistent with the leak.


I didn't get on the roof to check it but might be going back in
September when I will try to check it.


Any suggestions?


Thankyou in advance.