Black Streaks on my Roof

Do You Have Black Streaks on Your Roof?

What is that stuff? Have you looked up at your roof for the first time in a while and notice black streak marks running down your shingles? You might be wondering if it’ll come off or if it means your roof needs to be replaced. What is it anyway? Dirt, mold, mildew or defective shingles? It’s actually an algae called Gloeocapsa Magma which is usually spread by airborne spores or animals and it’s actually a blue-green color. This algae feeds on the limestone deposits in your asphalt shingles and then creates a protective, black coating around itself. So what are you supposed to do about it? If it’s starting to bother you or you’re thinking about putting your house on the market, you may want to consider cleaning your roof or calling the professionals to clean it for you. At USA Roofing & Gutters, we do not clean roofs; however we do install algae resistant shingles when replacing a roof. The shingles we install have copper lined granules, which helps inhibit the growth of algae to keep your roof beautiful.

How to clean it

Please be careful cleaning your roof yourself. Not only is there risk involved due to the danger, it’s also important to note that doing it yourself may void any warranties and/or your home insurance policy, so make sure to double check with your insurance agent or refer to your policy and shingle warranty first. With that being said, you can actually buy a cleaner specifically for getting rid of this unsightly mold or you can even make some yourself using these instructions from Tom Silva of This Old House.

Use a pump sprayer to wet down the roof with a mix of one part bleach to two parts water. Bleach will damage foundation plantings, so rinse them well with fresh water before you start and after you’re done. Then scrub the surface gently with a soft window-washing brush mounted on a telescoping extension pole. Don’t use a pressure washer, which could damage the shingles. Also, do this work from the safety of a ladder or from the ground, not by climbing on the roof.

Like Tom said, DO NOT get on your roof and be careful while using a ladder!

Can the black streaks be prevented?

The answer is a little complicated since algae spores travel fairly easily, so it’s difficult to completely and permanently get rid of them; however, there are preventative measures you can take that can help. If you already have asphalt shingles (that contain limestone), but haven’t noticed the black algae streaks, then we can put copper or zinc strips of metal along your roof ridges so that rain water will run over it and pick up ions that can prevent the algae. Pretty cool, isn’t it?

You have options when it’s time for a new roof too– you can ask about shingles with algae-resistant granules or go with a new metal roof.

The professionals at USA Roofing and Gutters are your trusted Birmingham roofing contractors and Huntsville roofing contractors so we can help with any roofing problem you may have, including algae growth on your shingles. Contact us today for a free inspection and estimate for any roofing needs you may have!

2 thoughts on “Do You Have Black Streaks on Your Roof?”

  1. Madaline Smith

    Thanks for the tips/ advice I was looking everywhere for a detailed explanation/ how to thanks again!

    1. usacrocker

      You’re welcome! We are glad our blog was able to help you!

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