What Causes Mold?
Molds need two main things: organic material like wood or paper for nutrients, and a moisture source. In search of these things, mold spores settle on surfaces just waiting for conditions to be right for growth.
As our buildings are full of wood and paper food sources for mold, the key to where mold will grow is moisture. For some molds the moisture source can be as scant as humidity levels over 50%, which is very common in basements, while other molds require pretty wet conditions like those found after flooding or a leak.
To avoid mold growth indoors always fix water leaks ASAP and monitor and maintain humidity at under 50%.
Drywall is an absolutely perfect growth medium for mold as it is two layers of cellulose (paper) with a middle layer of gypsum that holds water like a sponge. When you see mold on your wall it is likely that the back side of that wall is even worse as it is unpainted, meaning it is an easier food source for mold, and stays wet longer than the outside part of the wall.
Common conditions For mold growth
Humidity over 50%
Plumbing leaks
Leaks from roof, around doors or windows
Basement flooding or water seepage
Condensation on and around airconditioning ducts
Condensation on drywall from poorly insulated walls in winter
