How To Clean Mold and Mildew from Concrete
Concrete in your garage, basement and driveway is subjected to the intrusion of moisture and organic material carried by people, vehicles and the environment, and may not always be properly ventilated. This combination can provide a hospitable environment for mold and mildew growth. The growth of mold and mildew on concrete can not only cause unattractive stains, but can be hazardous to your health and spread to materials that you are storing nearby. Normally, bacteria and other organic growth will be less likely to flourish if the alkaline/basic pH of the concrete is maintained as it is not hospitable. For this reason, use a pH neutral or alkaline cleanser to help maintain a mold/mildew free concrete surface. Concrete base materials and surface treatments can vary, so test all cleaning solutions and application techniques in an inconspicuous location before using them in a wider area.
Scrape away any bulk mold and mildew residue from the surface. Use the appropriate protective clothing such as gloves and a ventilation mask, and work with disposable cleaning tools like paper towels and rags. Mix an alkaline cleaning solution using 1 gallon of hot water and 3 ounces (3 scoops) of a commercially available sodium percarbonate powder cleanser like Oxyclean. Scrub the stain directly with the cleaning solution, refreshing the cleaning solution as necessary. When the mold/mildew stain has been alleviated, rinse the area well with clean water. Blot any excess water with clean newspaper. As an optional finish, follow with an overall cleansing of a lightly sudsy solution of water and mild pH neutral dish liquid. Rinse with water, and blot with clean newspaper. Allow the area to dry thoroughly.
Keep an eye on the affected area over the next few days to watch for the reappearance of the stain, which would indicate continuing presence of mold/mildew spores. The treatment can be repeated, but keep in mind that severe, persistent or cyclical mold/mildew stains may require the assistance of a professional.
Caution: Never mix cleaning agents or chemicals, the result can be dangerous or deadly. Before cleaning, always test the agent on an inconspicuous location to determine its suitability and to make certain it does not damage the material. Wear appropriate clothing such as gloves and protective eyewear, and work in a well-ventilated area. Accidental inhalation or ingestion of cleaning agents can be hazardous and even fatal, particularly to pets and children.