Q At some time, my concrete basement floor was painted with latex paint over oil-based paint. When I try to clean it, the paint peels up. My basement is dry. What are my options for this 1912 house?
A It sounds as though the latex paint didn't adhere to the oil-base layer and that's what's peeling. Or it could be that there is moisture working its way through the floor and breaking the paint's hold on the concrete. That would be expected in an older home like yours. Many newer homes have a moisture barrier under the slab, so moisture migration isn't a problem.
To test for moisture, cut open a plastic garbage bag (or several). Secure to the floor by taping around the perimeter, creating a tight seal. After several days or a week, lift and check for moisture. If so, try to change the conditions that cause it. Basically, keep rain, snowmelt and sprinklers away from the foundation so the soil doesn't become charged with moisture, which is readily sopped up by concrete and passes through in the form of vapor. Make sure that gutters and downspouts discharge water at least 10 feet from the foundation. Adjust any hard surfaces that slope toward rather than away from your house.
When you've done as much as possible to eliminate moisture migration, you can paint again. But first you'll need to remove the existing paint. Scrape off all loose paint or use a chemical stripper. Scrub with hot water and a strong detergent or degreaser. Rinse thoroughly and let the surface dry for several days. Once the floor is clean and dry, acid-etch with phosphoric or citric acid, following label directions. (Home, hardware and paint stores sell these products.) When it's dry, paint the floor again.
An alternative is to leave the paint and cover the floor with wood laminate or a floating floor with vinyl.
Send your questions to Fixit in care of the Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-7032, or e-mail fixit@startribune.com.
