Tips for Cleaning Roof Stains – Algae

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Cleaning algae roof stains:Tips for Cleaning Roof Stains - Algae

I hate seeing black or green stains on a roof. There are many reasons that cause mold, lichen and algae to grow on a roof but that doesn’t mean you have to tolerate it. There are ways to eliminate these ugly stains and this article will show tips for cleaning roof stains and specifically algae stains off your roof.

People often ask me if these stains are a sign of roof wear. The answer to that is “no” the black staining is typically caused by algae and it will not damage the shingles, and it won’t make your roof leak. These stains usually show up on areas on the North side of a the roof or in areas that are blocked by trees or do not get much sunlight.

Blue-Green Algae:

The black mold-like stains and streaks that appear on roofs is usually a blue-green algae (Gloeocapsa magma) These stains mostly appear on light colored roofs but do grow on all roofs.

Roof Cleaner:

There are all types of consumer products that you can buy to remove algae stains off roof  but the best solution I’ve found is to use a mixture of two parts water to one part bleach and apply it with a garden sprayer.

For more tips on cleaning roof stains, click here.

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Robert Robillard is the editor of the blog, A Concord Carpenter, Assistant Editor of Tool Box Buzz and principal of a carpentry and renovation business located in Concord, Massachusetts. Rob hosts the Concord Carpenter... Read more

5 comments on “Tips for Cleaning Roof Stains – Algae

  1. T. Winston

    Thanks for this post! When in doubt though it’s good to go with a professional roof cleaner though, as you don’t want to risk damaging your shingles by scrubbing or power washing!

  2. Monica Chavez

    It’s interesting how you point out that black mold-like stains and streaks that appear on roofs is usually a blue-green algae. My mom and dad have several stains on the top of their roof, and they’re worried that it could be this blue-green algae. I think they should probably have a professional come and power wash it so that they can get rid of the stains.

  3. Trias Cello

    Thank you for this valuable information! Homeowners must educate themselves about cleaning the roof if you don’t have time to clean your roof its time to hire the best roofing contractor in your area that specializes in just roofs and provide the best quality service.

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