While obviously unsightly, the presence of mildew on interior or exterior surfaces is more than just a cosmetic problem. It's almost always an indicator of a deeper and potentially more destructive moisture condition.
Painting over it won't cure the condition, as the mildew will return sooner or later, and in the meantime the hidden moisture is working away at insulation, wood framing and other parts of your house.
Mildew, a form of mold, is most often seen as a black or sometimes white or greenish growth on siding, drywall, roofing and in other areas. In order to grow, mildew first of all needs a food source.
Because mildew likes organic materials, the typical home offers lots of choices, including drywall, wood, paper, wallpaper paste, cotton, linen, leather, wool and many other materials and surfaces.
In addition to the food, mildew will grow best in areas where it's moist and warm, and where there's a general lack of sunlight an...