Over the years, I’ve encountered mold-stained or mildewed wood on more than one occasion. During my career as a home-performance contractor, I used to see mold-blackened surfaces from time to time in locations where moist air was contacting a cold surface, such as the underside or back of OSB roof or wall sheathing. These days, I work as a project manager in a new-construction environment, but I still sometimes see surfaces where moisture has allowed mold to grow. In all of these cases, dealing with the situation requires two steps: Remove the source of moisture, and clean up the mold-blackened surface.
From experience, I’ve learned to rely on one particular cleaning product for cleaning up moldy OSB: MMR mold stain remover from Bad Axe Products (badaxeproducts.com). The formula for MMR includes sodium hypochlorite (which bleaches the wood and cleans up the mold stains) and some proprietary surfactants (which help the formula soak into the surface).
Before you handle this powerful chemical, you should be prepared. I follow manufacturer recommendations and suit up with DuPont Tychem 2000 full-body chemical protective coveralls and a full-face respirator with a P100 organic vapor cartridge, available online from Jon-Don janitorial products (jondon.com), which also supplies MMR. I don plastic gloves and tape the gloves to the protective suit sleeves. Then I pour the MMR into a hand-pump sprayer and spray it full strength onto any surfaces I need to clean.
The product requires no scrubbing. The powerful bleach starts to work within seconds and brings the blackened wood surface back to a lumberyard-clean, bright condition in less than a minute. Once the material dries (in a day or so), it leaves no residual trace.
