Black, gray or brown areas of fungus growth on the surface of paint or
Possible Causes Mildew paint
Forms most often on areas that tend to be damp, and receive little or
no direct sunlight (walls with a northerly exposure and the underside of
eaves are particularly vulnerable).
Use of a lower quality paint, which may have an insufficient amount of mildewcide.
Failure to prime bare wood before painting.
Painting over a substrate or coating on which mildew has not been removed.
Solution Mildew paint
Test to distinguish mildew from dirt by applying a few drops of household bleach to the discolored area; if
it disappears, it is probably mildew. Treat the mildew by applying a mixture of water and bleach, 3:1, and
leave on for 20 minutes, applying more as it dries. Wear goggles and rubber gloves. Then scrub and rinse
the area. Apply an exterior latex primer, then a top-of-the-line exterior latex paint in flat, satin, semigloss or
gloss finish, depending on the desired appearance.