Black, gray, or brown spots or areas found on the paint film or caulk bead.

Possible Cause:

  • Mildew forms most often on areas that tend to be damp, or receive little or no direct sunlight (e.g. bathrooms, kitchens, and laundry rooms).
  • Painting over a substrate or coating on which mildew had not been completely removed.
  • Use of a low quality latex paint.


Test for mildew by applying a few drops of household bleach to the affected areas; if he suspected mildew turns lighter in color or is bleached away, the discolorant is probably mildew. Remove all mildew from the surface by scrubbing with a diluted household bleach solution (one part bleach, three parts water), while wearing rubber gloves and eye protection. Rinse thoroughly. To protect against future mildew growth, use a top quality semi-gloss or high gloss latex paint. Clean regularly with common household cleaners that contain bleach. Take steps to remove excessive amounts of moisture from the area, i.e. dehumidifier. For high moisture areas such as bathrooms, consider installing an exhaust fan leading to the outside of the home.