Can you tell me what causes a black mold to form in the bathroom? It is mostly in the corners and edges between the walls and the ceiling. There is a ceiling fan. The bathroom does have a shower which is used regularly. This black mold also forms along the edges of some of the windows. Is there a moisture problem, if so how is it corrected? Is this mold harmful in any way, i.e. allergy? I listen to your show on NTR 650 here in Saskatoon, Saskatchewan but it is a bit early to call you(i. e. eastern time).
Answer:
Bathrooms should have 110 CFM (cu. ft./min.) exhaust fans vented to the exterior. Lack of adequate ventilation can cause mildew, peeling paint and blistering plaster. About the most effective way to control such a fan is to have it energized simultaneously with the light. Going a logical step beyond that would have the two of them on the same time delay switch so when it is turned off, both fan and light stay on for another 3 to 5 minutes. That gives steam a bit of time to cool and thereby become less harmful to wallpaper, paint, plaster and the like. Tub area tap flanges and soap dish need to be sealed to the walls to avoid injecting water into the wall cavity during showers and the like. If the tub slopes into the room as opposed to sloping toward the back wall it will cause a portion of shower water to flow onto the floor instead of back into the tub. That in turn, tends to deteriorate plaster in the effected area and eventually, to rot trim, underlayment, sub-floor and framework. This is not to even mention the attraction soap (usually containing at least some animal fat) and water have for all kinds of creepy crawlies.
