What Should You Do About Mold on Walls?

The CDC says mold will grow where there is moisture, such as around leaks in roofs, windows or pipes or where there has been a flood, and can grow in dust, paints, wallpaper, insulation, drywall, carpet, fabric and upholstery. The EPA says that if the moldy area is less than about 10 square feet, roughly a 3 foot by 3 foot patch, in most cases you can handle the job yourself, but that if there has been a lot of water damage or mold covers more than 10 square feet, you should consult its guide to mold remediation in schools and commercial buildings.

Porous materials are harder. The EPA says absorbent or porous materials such as ceiling tiles and carpet may have to be thrown away if they become moldy, because mold can fill their empty spaces and crevices and be difficult or impossible to remove completely. It says mold may be hidden on the back side of drywall, wallpaper or paneling, inside walls around leaking or condensing pipes, and on wall surfaces behind furniture where condensation forms. Investigating hidden mold requires caution, the EPA says, since removing wallpaper with mold on its underside can release a massive amount of spores, and if you believe you have a hidden mold problem, you should consider hiring an experienced professional.

Control the moisture. The EPA advises keeping indoor humidity below 60 percent, ideally between 30 and 50 percent, which can be measured with an inexpensive humidity meter, and acting quickly to dry the surface and reduce the moisture source if condensation collects on windows, walls or pipes, since condensation can be a sign of high humidity. Its Ten Things You Should Know About Mold gives a range of 30 to 60 percent, reached by venting bathrooms and dryers to the outside, using air conditioners and dehumidifiers, and increasing ventilation.