About 4 or 5 years ago I had my roof re-shingled, and as the main bathroom is in the center of the house with no natural light, I decided to have the roofers install a skylight. About 2 years ago, I noticed that the bead at the bottom of the skylight shaft joining the ceiling, began to show brown spots, almost like stains. The spots came off by wiping, but are back again. Also, the paint inside the skylight shaft as well as other parts of the bathroom ceiling is peeling, one place going right down past the drywall. I applied a primer before painting the ceiling and skylight shaft with an oil based paint when the skylight was installed. I also installed a 50 CFM fan in the bathroom. Up in the attic, the skylight is insulated, and so is the fan exhaust pipe. Why is the peeling taking place, and what must I do to prevent it?
Answer:
It's condensation. In small amounts but because there is no air movement in that area, it does build up and then undermines the paint or paper or whatever is there.
