Cement’s porous nature makes it vulnerable to mold in the presence of moisture or humidity. In fact, it takes as little as 48 hours for visible mold growth to appear on damp surfaces. Because of the serious health problems that mold can cause, it is important eliminate it as soon as possible so it doesn’t spread. From moldy basements to dingy walkways, there are some effective ways to control mold growth on your own when it affects a smaller area. For bigger jobs, it’s a good idea to call the experts.

Avoid Chlorine Bleach

The old school of thought regarding the elimination and control of mold on cement was to use chlorine bleach. However, more experts are moving away from this technique, particularly because the U.S. Environmental Protection Agency and Department of Labor advised against its use in 2013. While chlorine bleach is an effective disinfectant and cleaning product, it is best for use with certain types of fabrics and hard, nonporous surfaces. Many bottles state this on the label.

Chlorine bleach is not designed to soak into surfaces. Because it is 90 percent water, the chlorine dries quickly when you apply it on a surface, leaving behind mostly water (mold loves water) and dangerous fumes. Therefore, when you use it on cement with mold or mildew problems, it may eliminate the surface stains, but not the spores that you can’t see. Moreover, chlorine bleach is caustic and can breakdown or weaken cement.

When cleaning mold or mildew from cement surfaces, it is best to use non-chlorine, oxygen bleach-based detergents (like those that start with the word Oxy-) that penetrate the hidden spores within cement.

Mold Removal Tips and Techniques

  • When cleaning mold, ensure that the area is well ventilated and wear the proper safety gear:
    • N-95 respirator
    • Long gloves
    • Goggles
    • Long pants
    • Long-sleeved shirt
  • Scrub mold off hard surfaces with an oxygen-based detergent, following the manufacturer’s instructions. If the mold caused stubborn stains, you may use a pressure washer to remove them. Ensure that the pressure washer’s pressure setting is not too high, or you may damage the cement.
  • In addition to killing mold, you must also remove it. Do this with a wet/dry shop vacuum equipped with HEPA filters.
  • Allow the area to dry completely. Use a fan or dehumidifier if necessary.

Determining the Cause of Mold Growth & Preventing Future Mold Growth

It is important to note that killing and removing mold is not enough. You must also take steps to prevent its growth by identifying and remedying the cause of the damp environment. Moldy basements, for example, sometimes have moisture problems because of poor landscaping drainage, inadequate ventilation or leaky pipes. To help resolve the issue, you may need to adjust the landscaping grade so water flows away from the building, fix leaks or install a dehumidifier.

Another issue that you may encounter is the failure of moisture barriers, which are supposed to help prevent moisture problems in cement. If this is the case, you may need to replace the moisture barrier.

In addition to preventing mold growth by keeping the area dry, use a few coats of a solvent-based polyurethane acrylic sealer to help prevent water or moisture intrusion and mold growth.

If you have attempted to remove mold from a certain area several times, the spores might be in places that are too deep for detergents to penetrate. If this is the case, you may need to replace the affected concrete.

Professional Pressure Washing for Mold

If the moldy area is greater than 10 square feet, it is best to call a professional pressure washing service. The experts have access to equipment and powerful eco-safe detergents, and assume the health risks that come with mold cleanup. After the professionals finish killing and removing the mold, you must still remedy the moisture problem and seal the cement.

PWNA Safety Procedures

The Power Washers of North America, a group that informs members on best practices for safety in pressure washing. Make sure your technicians are ready for work, wearing appropriate clothing and operating power washers in a safe manner. Take time before each project to train our pressure washing crews on safety issues.