Mildew is a fungus (mold) that grows on many exterior painted surfaces, as well as on interior bathroom walls and other humid or poorly ventilated interior areas. If not corrected, mildew will continue eating the existing paint away, causing eventual paint failure in the affected areas. There is no way to absolutely prevent mildew growth, however, it maybe controlled if the proper precautions and recommendations are followed.


  • Failure to prime a bare wood surface before applying the paint
  • Painting over a surface previously infected with mildew
  • Excess humidity or other moisture problems


  • First, to determine if the problem is mildew, apply a few drops of bleach to the surface. If the dark color bleaches out in a few minutes, it is likely mildew, as dirt or other contamination would not be affected.
  • Locate and correct any sources of moisture accumulation or excess humidity.
  • Protect all plants and shrubs with dropcloths before cleaning the surface.
  • Clean the surface with a commercially prepared mildew remover or use a homemade solution of one quart liquid chlorine bleach, three quarts warm water and 1/4 cup ammonia-free liquid dishwasher detergent.
  • Rinse the surface and surroundings thoroughly with clean water.
  • Allow the surface to dry completely before painting.
  • Use an appropriate primer and then apply a high-quality paint in the desired finish.


Chlorine bleach must never be mixed with ammonia or with any detergent or cleaners containing ammonia. These mixtures will form vapors that can be harmful or even lethal. Gloves, goggles and protective clothing should be worn for protection.

Dunn-Edwards uses mildewcides in all exterior paints to resist new mildew growth. In addition, a fungicide or mildewcide may be added to the primer and paint if extra protection is desired.

Please note that these suggestions are provided as a service to you. We are unable to guarantee or be responsible for the results obtained by these procedures. If you have additional questions, ask any of our expert sales associates.