Q: We are remodeling our kitchen. When we opened one of the walls that adjoins a bathroom, we found water damage. It seems that every time the bathroom sink was used, water would leak inside the wall. The drywall and studs have mold on them. I know we need to get rid of the mold. However, do I need to tear out my bathroom wall as well as the mold? The mold is visible only on the gutted portions; it has not penetrated into the bathroom itself.
A: We hate surprises, but tearing out a wall often means you’ll be confronted with the unexpected. The older the home, the more likely something strange is going on behind the walls.
You’re lucky you caught the leak before any further damage was done. A little mold and mildew are easy to deal with. If the leak had been allowed to linger longer, it’s likely that the framing and flooring would have developed dry rot. That would mean replacement with new material, which could be a big job.
Tearing out the bathroom wall won’t be necessary. But some remediation needs to be done. It sounds as if the damage is only in the area of the leak, so that’s the only area you’ll have to treat. It’s also good you’ve got the wall open as part of the remodel. That makes the work you’ll have to do easy.
Mold requires three things to live and propagate: food, the right temperature and moisture. The food is the drywall and wood in your walls. The controlled space in the kitchen and bath provides the right temperature, and the leak provided the moisture.
You can’t do anything about the first two, but the moisture will go when you fix the leak. We assume you’ve already repaired the drain and vent pipe and that the leak is gone.
After the leak is repaired, let the area dry thoroughly. A week to 10 days should do the trick. If you want to speed up the drying process, point a small electric space heater at the area. But don’t leave it unattended. You wouldn’t want to burn down the house.
Once the area is dry, check for possible dry rot by poking the wall framing with a screwdriver. If you detect a small area of rot, you can treat it by digging out the debris and brushing the remaining wood with a wood preservative.
Next, wash the entire area, including the wallboard, with a 50-50 solution of chlorine bleach and water. Rinse the bleach residue off with clear water and let the area dry.
Finally, paint the entire area with a good latex primer laced with an antifungal additive. Once you’ve completed this process, your mold problem should be a thing of the past.