How to Remove & Prevent Mold & Mildew on Concrete Block Walls

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Things You'll Need

  • Gloves

  • Ventilation mask

  • Goggles

  • Plastic scraper

  • Stiff brush

  • Bucket

  • Water

  • Detergent

  • Bleach

  • Plastic garbage bag

  • Paint brush

Mold should be killed before it spreads.

Molds are microscopic organisms that thrive in damp places with poor ventilation. Mildew is mold at an early growth stage. Mold performs an invaluable role in nature's regeneration process. Without mold, dead organisms would not decay. Unfortunately, mold often shows up in such areas as concrete basements, bringing with it the potential for significant damage to your health and home. Removing mold and preventing its return are imperative for any homeowner who recognizes mold's damp, pungent odor in the home.

Step 1

Put on the mask, goggles and gloves. Identify areas of mold growth. Only mold grows on concrete blocks, so identifying mold is simple. Look for dark, hairy-looking spots (mildew), jelly-like growths and small mushrooms. All are forms of mold.

Step 2

Scrape away all surface mold and mildew, and place the scrapings in a plastic garbage bag.

Step 3

Clean the area with a stiff brush and a mixture of hot water and detergent. Rinse with clean water and dry the area with paper or other disposable towels. Put the towels and scraper in the plastic garbage bag.

Step 4

Open the windows if you are inside. Disinfect the area with a mixture of bleach and water (1/2 cup of bleach per gallon of water). Allow the area to dry naturally. Do not mix bleach with an ammonia-based cleaner; mixing them causes toxic fumes.

Step 5

Apply a coat of clear concrete sealer to prevent the mold from returning. Search for leaking pipes or other sources of water. Repair any leaks and explore options for increasing ventilation in the affected space. Dispose of the trash bag.


Address dampness immediately; mold develops in less than two days. Mildew is mold; don't let commercial products fool you. Consider putting a dehumidifier in damp, poorly ventilated areas.


Robert C. Young

Robert C. Young began writing professionally in 1989 as a copywriter for an advertising specialty company. From 2000 to 2007 he operated a real-estate development and construction company. His work has been published online at SFGate and various other websites. He graduated with a Bachelor of Business Administration in economics from Georgia State University.