Cinder block walls are strong, long lasting and resistant to elements such as wind and rain, however, they are still subject to the effects of mold growth. If dirt settles on a cinder block wall and moisture collects as a result from flooding, humidity or rain, mold spores can settle on the wall surface and begin to expand. If you notice patches of mold on your cinder block wall, take action at once.
Vacuum the wall. For best results, wait until the wet weather has subsided and the wall has dried considerably. If that is not an option, vacuum the wall surface using a wet-dry vacuum. Otherwise, the EPA recommends vacuuming the cinder blocks with a HEPA vacuum, to draw out the impurities. Remove as much of the mold as possible.
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Put on rubber gloves. Mix 3 quarts of water and 1 quart bleach in a bucket. Add 1 ounce of powdered detergent and 1 ounce of sodium orthophosphate and mix well. Sodium orthophosphate is sometimes marketed as trisodium phosphate and is sold in home-supply stores.
Apply the mixture directly to your cinder block wall wherever mold appears using a sponge or with a spray bottle. Apply enough to penetrate the mold and allow the mixture to remain on the wall for about five days before you proceed.
Put on rubber gloves. Scrub the wall with a firm wire brush to loosen and remove any remaining mold particles. Rinse the wall with cool water and allow it to dry. Vacuum again to eliminate the dead spores.
Clean your cinder block wall regularly with water and mild detergent. Keeping the wall clean deprives mold spores of necessary nutrients and prevents active mold from returning. At the very least, spray the wall from time to time using a spray nozzle to blast away the accumulated dirt.