It is important to understand the simple basics of what it takes for mold to grow. There are four things which, if present, can bring about mold growth. These are:
1. Mold spores:
Mold spores are everywhere in our normal environment, including at least a few inside our ceiling and wall cavities.
Roof leaks, window leaks, plumbing leaks, groundwater intrusion from patios; any of these can result in building materials getting wet. Even high humidity which results in condensation on surfaces can be sufficient for some varieties of mold to grow.
Food is any organic material that the mold can digest. Excellent food sources for mold include drywall paper, wallpaper paste, and MDF baseboards.
In the correct temperature range (many molds thrive throughout the human comfort range).