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How To Remove Algae From Your Asphalt Roof Using Oxygen Bleach

by Tara Pena

One of the methods of removing algae growth from an asphalt roof involves the use of oxygen bleach. Other bleaching products such as chlorine may work, but oxygen bleach is best because it is not toxic to the environment. Read on to learn how you can use it to clean your algae-infested roof.

The Requirements

Here are the supplies you need:

  • Oxygen bleach
  • Slip-resistant shoes, safety goggles and gloves
  • Ladder
  • Backpack sprayer
  • Water
  • Garden hose
  • Safety rope

The Conditions

For the bleach to work, it needs to stay on the roof for several minutes. This means you should not do the cleaning on a very sunny day when the solution will just evaporate off the roof fast. At the same time, you should not do it on a rainy day because the rain might wash it off. A perfect day would be dry and overcast.

Safety Concerns

As an amateur, you face more danger working on the roof than a professional roofer. Therefore, you shouldn't try it if you don't have a buddy to help you in case of an emergency. Even with a buddy, there are several safety precautions you should take such as:

  • Wearing slip resistant shoes (rough soles)
  • Wearing goggles and gloves
  • Avoiding DIY projects on steep roofs
  • Having a strong ladder
  • Using a safety rope

The Procedure

Once you have everything ready, mix the oxygen bleach with water and pour it into the sprayer. Check the mixing ratio on the bleach's user instructions, they may vary by manufacturer.

Next, climb onto the roof and spray it with the solution. A backpack sprayer is good because it frees your hands for maneuvering in case you stumble. Remember to spray the entire roof, and not just the dark patches of algae. If you just concentrate on the patches, then your roof will have light (bleached areas) and dark (unbleached areas) areas when it dries, which isn't pretty.

Once you have covered the whole roof, leave the solution to sit and soak into the shingles for a few minutes. If the algae growth is particularly bad, you can use a scrub brush (or a stiff broom) to scrub them off the roof. Just make sure you do it gently so that you don't remove the granules.

After the wait time is over, take your garden hose and thoroughly rinse off the bleaching solution.  Don't use a pressure washer or an overly focused stream of water because that may damage your shingles' granules too.

This will get rid of the algae from your roof, but it is only a temporary measure. If you don't want to do it regularly, then you should get a roofing contractor to install strips of copper or zinc metals on your roof. The metals are algae inhibitors and prevent their growth.