Sweep the wall to remove any dust build-up and loose debris. Use a push broom, dust broom or bristle brush.
Remove any loose or peeling paint from the wall with a wire bristle brush. Scrape across the surface to break the paint off. If the wall is brick, scrape across the entire surface of the wall to remove any loose brick that has decayed.
Scrub the wall with hot soapy water mixed with a mildew cleaner. You can use a nylon bristle brush to scrub the wall. Once scrubbed, allow time for the wall to dry.
Fill in any vertical cracks in the wall that are no less than ¼-inch thick with a polyurethane sealing caulk. If you have vertical cracks wider than ¼-inch or you have horizontal cracks, consult a structural engineer before continuing to ensure the foundation does not require major repairs. If given approval by the engineer, fill in the remaining cracks with the polyurethane caulk.
Place a dehumidifier into the basement and reduce the humidity to a range between 50 and 60 percent humidity.