Q.: For the past 5 years our 12-year-old cathedral dome has been showing moist spots on the interior surface whenever it rains or snows. The moisture is not uniformly distributed over the surface, so it is not condensation. About 3 or 4 years ago a thin seal coat was applied to the exterior surface but it didn't reduce the leakage. What do you recommend for repairing and sealing the dome effectively?

A.: We suggest you ask two expert waterproofing contractors in your area to examine the dome and make recommendations as to whether or not you have small cracks that need to be repaired by injection. If there are small cracks that are of no structural significance the contractors may be able to seal them by injecting a urethane foam designed for the purpose. Structural cracks may have to be repaired by injecting with epoxy. If the problem is not too severe it may be possible to prevent leakage without injecting the cracks but by applying a neoprene-hypalon coating system to the exterior.