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  • Writer's pictureJason Gentry



Tired of looking at those black streaks, or even moss covering your roof? Worried about the potential damage this organic growth is causing to your asphalt shingles? Considering replacing your roof because of these unsightly stains? Don’t replace your roof. Just clean it! No need to worry any longer about the eye soar and potential damage mold, mildew, and moss is causing to your roof. Roof cleaning is as much a part of routine home maintenance as any other task. Roof cleaning will not only keep your home looking its best, but it will protect

your home from damage often caused by organic debris and moss build-up. If your roof is less than 20 years old but is looking a little worn, you should consider having it professionally cleaned.

What Are the Black Streaks on My Roof?

The black streaks on your roof are caused from Gloeocapsa magma which is a species of cyanobacteria.

These cyanobacteria are responsible for creating the unattractive black roof stains and/or streaks commonly noticed by many. The bacteria accumulate over time; this accumulation begins to show the problematic black stains as the cyanobacteria develop their dark and hard UV-protective outer coating.

The main reasons for the rapid spread and noticeability of these cyanobacteria are:

  • Gloeocapsa magma spores are spread mainly by wind but also by animals and locate themselves on the north side of roofs where the lack of sunshine stimulates their growth and formation

  • Rising humidity and temperatures combined with more and more bacteria spores promote their spread with these favorable conditions.

  • A predominate filler used in composition shingles, because it is so plentiful and inexpensive, is limestone. It is the calcium carbonate in limestone that Gloeocapsa magma really likes to feed off, along with moisture that naturally collects on a roof’s surface. Once the algae growth becomes noticeable as those dark streaks on the roof, gravity and rainwater flowing down the roof carry the spores down the roof, causing the commonly seen pattern of streaks extending downward on the roof. And, as the algae feeds off the limestone over time, it invades the structure of the shingles and shortens their lives.

Is Gloeocapsa Magma Dangerous?

Besides looking very unsightly and diminishing any home’s curb appeal and value, what other damage can Gloeocapsa Magma roof algae do? When roof algae are not taken care of, they stop the shingles from reflecting heat from the sun’s UV rays. When this happens, it can affect your home’s heating and cooling costs without you even realizing it. Also, because the shingles cannot reflect heat they start to diminish prematurely. Signs of wear are curled corners, wavy or humped shingles, broke or loose shingles, and an excess of shingle granules appearing in your gutters just to name a few.

What Can I Do to Help Prevent Gloeocapsa Magma?

  • Trimming tree branches back to allow more sunlight to reach the roof and minimize debris accumulation will provide an environment less inviting for such growth

  • Debris that does begin to accumulate on the roof should be cleared regularly with a leaf blower or similar, non-abrasive method as part of a regular maintenance program.

  • Air flow should be directed down the slope to avoid driving debris under the edges of the shingles.

  • Keep gutters clean to promote proper water drainage. Do not allow gutters from an upper roof to drain directly on a lower roof; extend the downspout from the upper roof into the lower gutter.

How Do I Get Rid of Gloeocapsa Magma?

One of the fastest and most effective methods of getting rid of Gloeocapsa Magma from your roof's surface is with a professional roof cleaning. At Gentry Surface Restoration we use a low-pressure cleaning process which is the only process approved by ARMA (Asphalt Roofing Manufacturer’s Association) for cleaning an asphalt shingle roof. This process will not void your roof’s warranty or impact your insurance.

Want to learn more about our cleaning services or receive free estimate? Click Below



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