they make this great stuff for icedams compensation these days. It is a roll of Shingle material that is peal and stick on the back. It is about 4 feet wide. You put it down as a solid layer before shingling and then the lake formed by the icedam can't seep through. So easy to apply.... but would require reroofing the building. That or just get some of the heating things that go around the gutters and melt the dams.
I think the major damage was caused by ice dams, but you know what? I'm thinking now that condensation is forming on the underneath side of the metal roof and running down, then into the wall down there at the end! The gutters are clear, I just checked, and draining well...
There is still a good inch of ice still on the top of the shop in all but a couple of areas...so you've got warm air in the shop coming in contact with that ice cold tin roof (it's almost 50 degrees out there now.)
I vacuumed up as much of the flood as I could, but it's still dripping. I put down buckets, turned on a fan and turned on a dehumidifier. Probably don't want to heat up the shop though...