Algae Stains and Roof Discoloration:
Best Way To Remove Them?

Algae stains are caused by airborne particles and look like mold or mildew. If you see stains or discoloration on your roof (see photos below), follow these steps:

  1. Protect bushes and shrubbery around the perimeter of house by covering with plastic.
  2. Combine one cup of trisodium phosphate, one gallon bleach and four gallons of water in a bucket or hand-held sprayer.
  3. Spray the stained areas and let the solution sit for ten or fifteen minutes.
  4. Lightly rinse with water and/or use a soft scrub brush for stubborn areas. Try not to remove the protective granules on the shingles. Avoid using a pressure washer for this reason.
  5. Repeat the process if necessary.
  6. When finished be sure to rinse bushes and shrubbery thoroughly to remove any remaining solution before it dries.

(click photos for larger view)