By Dwight Barnett
Q: I have had mold buildup on the walls of my master bedroom, and I have been managing it by washing it down every year or so. But it comes back even though I keep it ventilated. It is the only room in the house with this problem. It tends to be damp and the other rooms are dry. The only difference is that the bedroom is a step down and lower than the rest of the house. There is a crawlspace, and during the raining season it will get wet. But there’s no standing water and it tends to dry up as summer comes and goes. I was told to paint the walls with mold-resistant paint, but I read that this would not solve my problem. Please advise.
A: Mold thrives in dark, damp and warm environments such as a closet or where furniture is placed tightly against an outside wall. Mold needs three things to survive and grow: water, warmth and a food source. Your drywall is an ideal food source because the paper on both sides of the drywall contains cellulose, the basis of all paper.
If you see mold on the room side of the drywall, there is a 90 percent chance there is a larger area of growth on the backside of the drywall in the dark, often-damp recesses of the home’s structure.
By cleaning the mold, you are adding water to the already affected area, thereby aiding in the growth and expansion of the mold problem. I often hear stories of homeowners using household bleach to clean mold, but bleach only adds to the problem.
According to the Clorox Company, “Regular Clorox bleach contains water, sodium hypochlorite, sodium chloride, sodium carbonate, sodium hydroxide and sodium polyacrylate, in descending order of concentration.” Therefore, do not use bleach to clean away mold.
Because the bedroom floor is lower than the other rooms in the home, the floors are closer to the damp soils of the crawlspace and I would assume the room is on the northwest side of the home. The northwest is the coldest side of the home, where condensation forms in colder months. As the soils under the floors dry, they release warm moisture-laden air that finds its way to the wall cavities of the bedroom.
The moisture-laden air condensates and feeds the mold on both sides of the wall.
My solution would be to first locate the electrical wiring inside the walls so that you do not accidentally cut the wires.
Next, use a drywall saw to remove the affected drywall, discarding it outside of the home. Remove damp or moist wall insulation and any vapor-barrier materials you encounter. Allow the wall cavity to dry before replacing the insulation and drywall.
Wearing a painter’s mask and rubber gloves, go into the crawlspace to inspect the floor joists and floor decking for mold. Use a wire brush to remove any mold found on the wood surfaces.
Severe cases of mold growth in a crawlspace will require a treatment performed by a mold-remediation contractor. Add a 6-mil-thick plastic ground-cover vapor barrier over the entire crawlspace floor to restrict moisture migration. If water in the crawlspace is an ongoing problem, a foundation drainage system needs to be installed.
What I am advising you to do is to eliminate the water and moisture source that feeds the mold. In more severe cases of mold growth, a dehumidifier is temporarily installed in the crawlspace to alleviate the humidity problems and allow the wood-floor system to dry.
The mold will always be there in the wood, but when dry, it goes dormant. Wood is considered dry when it contains less than 19 percent moisture by content.