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musty smell on old drywall

I have lived in a 65+ year-old-house on a slab, no crawl space, for almost 20 years. I used to have two window air conditioners, but I still had trouble with moisture on my walls. I got central air a few years ago which seemed to help greatly. My problem is that I was going to paint my walls, and there was some peeling paint so I started peeling and before I knew it, I had almost all of the paint off the wall. The drywall smells "musty" like a damp basement. The walls are dry but have a chalky substance on them. It also appears these walls were never primed appropriately. Is there something I can do to "clean up" the walls so I can prime and repaint?

Thanks a bunch!

Re: musty smell on old drywall


You state, "I still had moisture problems on my wall". Do you mean you had condensation to the point it would run down the wall? A 65plus year old house would probably have had minimal insulation.

You don't state where you live, a hot or a cold climate. I assume you are in a hotter climate because you have always had A/C. In very warm climates, the vapor barrier is often put on the exterior wall, especially when the house is air conditioned. Airborne moisture tries to migrate to the less humid area. In Florida, for example, the outside air is more humid than the inside air-conditioned air. If moist air is reaching the back of the cool, air conditioned inside wall, you could be getting condensation on the back side of the drywall. Mold and moldy smells generally need moisture to exist. Some how you must stop the moisture from entering the wall cavity. I think I would consult with a qualified contractor or architect in your area to see what steps might be taken.

You also state that your house is concrete on grade. If a vapor barrier was not placed under the concrete, you are probably taking a lot of moisture from the floor also. If your heat registers are in the floor, you might be able to see if plastic is visible right under the concrete. Otherwise, it would be difficult to know if it is there. You can test for floor moisture by taping a heavy piece of plastic, such as a piece of heavy garbage bag, to the bare floor for 24 hours. If when you pull it , you see moisture on the back, you have a problem.

You don't state what kind of flooring you have, carpet or hard flooring. There are vapor proof barriers that can be put under both types, but of course, the flooring would have to come up first to do so.

As to how to re-paint your peeling walls: It is hard to know what was used 65 years ago as a primer. Drywall was in its infancy right after World War Two. At this point, I would scrape and sand the loose paint the best I could. Then I would prime the exposed drywall with a quality acrylic drywall primer. After it dries, "feather" in the areas where it transitions to the paint still stuck on the wall with drywall compound. Sand those patches, spot prime, and then prime the whole wall with a good acrylic primer. Finally, paint your walls.

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