Mildew

Black, gray, or brown spots or areas on the surface of paint or caulk.

Possible Cause:

• Forms most often on areas that tend to be damp, or that receive little or no direct sunlight (e.g., bathrooms, kitchens and laundry rooms).

• Use of an alkyd or oil-based paint, or lower quality latex paint.

• Failure to prime a bare wood surface before applying the paint.

• Painting over a substrate or coating on which mildew has not been removed.

Solution:

Test for mildew by applying a few drops of household bleach to the discoloured area. If it disappears, the discolourant 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. Power washing is also an option. Rinse thoroughly, prime any bare wood, then apply one or two coats of high quality exterior paint. To protect against mildew in high humidity areas, use a quality kitchen and bath paint.