Q: My wife and I are getting ready to sell our house. We have a white substance on part of our basement walls. I have been told that it is efflorescence. The parts of the walls where it appears are below ground, but it’s only on a portion of the walls. Do I need to get this off the walls before selling the house? Is it harmful? It is hard to clean off. Am I better to hire someone to do it?
A: Yes, it is efflorescence, which is lime being leached out of the concrete by water. It is harmless but annoying, and scary for the uninitiated. The walls are wet from condensation of warm, humid air escaping into the basement. It can be corrected by venting the basement and insulating its ceiling with 9-inch fiberglass batts with the paper vapor barrier up, touching the ceiling boards between joists. Or insulate by inserting 4 or more inches of rigid foam insulation. Sweep it off with a broomIt will come back if you don’t do something about it.
Q: I have brown water stains on a ceiling. Home Depot suggested spraying the stains with white Kilz spray, then a coat of white latex ceiling paint.
A: That will work, but don’t forget the mold in the middle of that stain. Treat it with 1 part bleach and 3 parts water, and continue over the entire ceiling with this solution, which can also take off other stains. Be careful using Kilz because it is so intensely white that it is hard to cover with one coat of paint. So if you use the Kilz, do the entire ceiling (in that room) before using the ceiling paint.