Clean Mold in a Basement

Put on protective gear before inspecting or cleaning mold. Find out the size of the affected area, then decide if you prefer to hire a professional. To clean it yourself, apply a mold-killing cleaning agent such as diluted bleach, undiluted vinegar, or 3% hydrogen peroxide. Let the solution sit briefly, then scrub and rinse the area. Eliminate any leaks, condensation and excess humidity, since reducing moisture is the most important way to combat basement mold.

Steps

Evaluating the Scope of the Problem

1. Put on protective gear first. Wear old clothing and long gloves that extend to the middle of your forearms. Put on an N-95 respirator, and follow the instructions that came with it to ensure a proper fit. Wear goggles without ventilation holes.
   • You can purchase an N-95 respirator mask online or from a hardware store for about $12 to $25.
   • Inspecting for mold can stir up airborne spores, so it’s important to wear protective gear.
2. Check the HVAC system for contamination. Look for mold near the intake of your heating/ventilation/air conditioning system. Inspect inside the air ducts for a musty smell or noticeable mold growth. If all you find is dust in the return registers, that’s normal and you can vacuum or remove the registers to clean them.
   • If you don’t find any signs of mold, and no one in your household has unexplained illness, symptoms or allergies, your air ducts are most likely not contaminated.
   • If you suspect contamination in your HVAC system, turn it off and don’t run it until you have the air ducts cleaned.
3. Recognize when a professional service is needed. Contact a professional mold removal service if you find a strong odor, damage from contaminated water, and/or areas of mold larger than ten square feet (three meters), approximately three feet by three feet (91 cm by 91 cm). Read online reviews or obtain a referral for a qualified mold remediation contractor. Check their references and ask what EPA recommendations or other professional guidelines they’ll follow.
   • For large areas of mold, the basement and HVAC may need to be sealed off with plastic sheeting.
   • Contaminated water can occur from flooding or sewage backup.
   • A strong, moldy odor may indicate unseen mold growth behind walls, under flooring or beneath baseboards.
   • You may be able to obtain a free estimate detailing what services are needed. The average cost for mold remediation is about $7,500.

Removing the Mold

1. Ensure proper working conditions. Ventilate your working area as much as possible. Open windows and doors, and use fans. Wear the same protective gear you did when you were inspecting: old clothing, long gloves, an N-95 respirator, and goggles without ventilation holes.
2. Remove contaminated items. Take any moveable items from the area outside to inspect them. Throw away disposable items like cardboard boxes. Wash and dry any contaminated clothing. Clean contaminated items before returning them to the basement, once you’ve finished cleaning the basement mold.
   • You can deep clean leather, wood or inorganic furniture.
   • Upholstered furniture with visible mold will need to be disposed of or reupholstered by a professional.
   • Don’t store cellulose-based items, such as cardboard, paper, or firewood in your basement.
3. Clean or replace carpeting, if applicable. If you see visible mold on the surface of carpeting, sweep it with a broom to loosen the mold. Use a vacuum with a HEPA filter to vacuum the carpeting. Apply a cleaning solution and scrub the area. Allow the carpet to dry completely.
   • If the carpet is removable, let it dry outside in the sunshine. If not, turn fans on to help the carpet dry.
   • Dispose of any carpeting that’s been soaked through.
4. Choose a cleaning agent. Perform a small test area first on each item you’re cleaning to make sure the cleaning agent doesn’t damage it. You can clean mold with diluted bleach, diluted Borax, undiluted vinegar, a baking soda solution, or 3% hydrogen peroxide. Depending on which method you choose, you can use a bucket or spray bottle to hold the solution.
   • For hard surfaces, combine a gallon of water with a cup of bleach, or one part bleach to sixteen parts water. For porous surfaces, try one part non-ammonia, liquid dish detergent, ten parts bleach and twenty parts water.
   • To use baking soda, combine 1/4 to 1/2 teaspoon (1 to 2 mL) baking soda with a full spray bottle of water. Alternately, combine 1/2 cup (118 mL) baking soda with one cup (250 mL) of water and one tablespoon (15 mL) of mild liquid detergent.
   • Borax is safe for porous and nonporous materials. Combine a cup (225 mL) of Borax with a gallon (4 L) of water.
5. Apply the cleaning agent and allow it to sit. Use a spray bottle, a sponge or a rag dipped in your cleaning agent to apply it to the moldy area. Allow the cleaning agent to sit for five to fifteen minutes.
6. Scrub the area with the cleaning agent. Use a scrub brush or cloth to scrub the area with your chosen cleaning agent. Make sure to get into hard-to-see areas like cracks and crevices as well as the visible surfaces. Rinse the brush or cloth often to avoid spreading mold residue.
7. Rinse the area with clean water. Use a clean sponge or rag to wipe down the area with water. Change the rinse water regularly to keep it clean. Once the area dries, check for any mold you may have missed. If you still see signs of mold, repeat the scrubbing and rinsing process.

Reducing Moisture

1. Control the humidity. Increase the ventilation in your basement. Run air conditioners and dehumidifiers as needed. If you have a humidifier, clean and treat it with an antimicrobial solution.
   • You can increase ventilation by using oscillating fans, opening windows and doors, and using a dehumidifier.
   • You can purchase antimicrobial solutions online or at a hardware store.
2. Check major appliances for proper venting and drainage. Make sure your large appliances, such as your washer and dryer, are vented. Your washing machine needs a floor drain and secure hose connections. Install a pan for overflow right under the machine, if needed.
3. Check your gutters and pipes. Ensure that your gutters discharge water at least six feet away from exterior walls. If your gutters are sending water too close to the home, install gutter extenders. Look for leaky pipes, and repair your piping, if needed.
   • Sump pumps should discharge water at least twenty feet from your home.
4. Check the perimeter of the home. Ensure that the ground slopes away from the house so that water won’t pool up against the foundation. Clear away any wet leaves against the exterior walls and don’t allow debris to accumulate there.
5. Check your air conditioning pan and duct joints. Clean the condensation pan under the coil of your central AC with a 1/2 percent bleach solution. Check that the continuous drain is functioning. If you find any leaky duct joints, seal them with flexible mastic, which you can purchase at a heating and cooling supply store.
   • Clean the AC condensation pan before each cooling season.
6. Ensure that you have proper insulation and waterproofing. Make sure your roof is insulated, and there are no leaks in your roof or ceiling. Insulate your Insulate Windows with proper flash and caulking to minimize condensation. Waterproof and insulate exterior walls.
   • You can have your basement waterproofed professionally, or apply sealant to your walls and floors. Fill in any cracks with a waterproof filler.
7. Replace vinyl wallcoverings, if applicable. Remove any vinyl wallcoverings, which trap humid air between drywall and the wallpaper. After fully cleaning the area, use paint or wallcoverings with permeable paper backings instead.
8. Cover any bare earth flooring. Unfinished basements or crawlspaces with bare earth flooring transmit a lot of moisture. Have flooring put in, or do it yourself by covering the area with 6-mill poly sheeting. Make sure the basement is heated, cooled and humidified equally with the rest of the house.

Tips

• Clean your basement weekly and vacuum it with a HEPA vacuum to help prevent mold.

Warnings

• Consult with a health professional before starting cleanup if you have concerns about your health, such as allergies or respiratory problems.
• If you’re using a strong disinfectant, such as bleach, wear gloves made from natural rubber, nitrile, neoprene, polyurethane or PVC.
• Never mix bleach with products containing ammonia or other chemical cleaning agents. Don’t mix multiple cleaning solutions unless you’ve confirmed that it’s safe to do so.
• Don’t touch any mold or contaminated items with your bare hands.
• Mold can be cleaned, but may cause permanent staining or cosmetic damage.
• Clean all moldy surfaces before applying any paint or caulk.

Things You'll Need

• Old clothing
• Long gloves
• N-95 respirator
• Safety goggles
• Cleaning agent of choice
• Bucket or spray bottle
• Scrub brush or rags
• Clean sponge or cloth

Sources and Citations

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