How to Remove Mold From Your Roof

In recent years, roofing manufacturers have begun mixing copper granules into roofing products to produce algae resistant shingles. If you live in an area susceptible to algae growth, be sure to specify this type of shingle when replacing your roof.  If for some reason you have already gone through roof repairs or replacement and see algae stains on your roof that you’d like to try and remove yourself there are some tips. 

Algae stains can be removed by cleaning, though they usually return. While an occasional cleaning might not harm your roof, repeated use of harsh chemicals, or the erosive effects of pressure washing, can damage or shorten the life of asphalt shingles. There are several products on the market specifically designed to remove algae stains from roofs, such as Wet & Forget and Moss Out. A mixture of trisodium phosphate (TSP), bleach, and water will also remove stains. Oxygen bleach lightens stains as well and is less harmful to the environment, but it doesn’t produce as immediate or dramatic an effect as chlorine bleach.


Heres what you’ll need:

  • Cleaner
  • Pump sprayer
  • Garden hose with spray nozzle
  • Safety glasses or goggles
  • Rubber gloves
  • Safety rope
  • Old clothes
  • Slip resistant shoes
  • Ladder


If you’re concerned that you may damage your plants or lawn, here are some other tips to help with that process of preparation.


Working on a roof can be dangerous, and it becomes even more hazardous when wet, so be sure to take adequate safety precautions. Avoid working on steep roofs, wear slip resistant shoes, and use a safety rope where needed. When working with harsh chemicals, be sure to protect your skin and eyes. Bleach can damage or kill other plants in addition to algae, so wet down any grass, shrubs, or other plants where runoff will occur before and after applying bleach. Covering bushes with plastic after wetting them down help as well.



It’s best to clean your roof on a cloudy day to prevent the cleaner from evaporating too quickly. If you know the manufacturer of your shingles, contact them or check their website for specific recommendations on cleaning. When using a product made for cleaning roofs or oxygen bleach, follow the directions on the container.

While the recipe for cleaning a roof with bleach can vary, the basic formula is:

  • 1-quart bleach (6% sodium hypochlorite)
  • 1-gallon water
  • ¼ cup TSP (trisodium phosphate) or other heavy duty cleaners (don’t use a cleaner that contains ammonia or is not recommended for mixing with bleach, as it can result in poisonous chlorine gas)

Pour the ingredients into a pump type garden sprayer, mix well, and spray. After wetting down the roof with the solution, allow it to remain on the roof for about 15 minutes before rinsing off with a hose.

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