Fix any plumbing leaks and cracks that are allowing in external water before you start spraying away at the mold. You don't want your hard work undone by providing moisture for a new mold infestation.
Prepare a solution of a half gallon of 10 percent hydrogen peroxide (H2O2) with a cup of boric acid. Don't use the 3 percent solution that drugstores sell; that won't make a concentrated-enough antiseptic. Dilute 35 percent H2O2 if 10 percent isn't available.
Thoroughly moisten the black mold before scrubbing. Otherwise, you can send spores airborne, spreading the mold to new surfaces.
Scrub the mold off in layers. Scrub off only moist mold, then re-wet it. Then scrub off another layer. And so on.
Soak the surface with solution after all the mold is gone, so it seeps in deep to get any small invisible growths.
Things You Will Need
- 10 percent hydrogen peroxide
- Boric acid
- Use a facemask when scrubbing black mold, and take breaks if hay-fever-like symptoms overwhelm you.
- Cut out a piece of the wall if the mold seems to go all the way through. See if the other side of the wall has mold too. You may have to replace a large part of the wall instead of just spraying and scrubbing it.
- After removing all of the mold, install a dehumidifier in the room and run it 24/7, emptying the water bin regularly.
- Install fluorescent lights near the mold infestation. Leave them on a few hours each day so the small amounts of UV light keep the mold from growing back. A tanning lamp emits more UV, but requires wearing protective eyewear.