Black Streaks from Algae on Your RoofIn the Raleigh area, black streaks on roofs are a common sighting.  It’s not only ugly, but also insurance companies are starting to require that you have it removed or they may cancel your homeowner’s policy.

The good news? Your shingles aren’t destroyed, and you don’t need a new roof.  What you have is prehistoric gleocapsa magma, or more commonly known as roof algae.

Below are some common questions we hear about roof algae:

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Prehistoric Roof Algae?

Yes!  The algae on your roof is from a family called “cyanobacteria”, or blue-green algae.  It has been on Earth for over 3 billion years!!  Gloecapsa magma is the species that causes those lovely black streaks on roofs in our area.

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How Did It Get There?

Roof algae arrives on your roof as either spores or clumps of cells.  You may have noticed that the streaks only seem to grow on one side of your roof.  That is because the sun is less harsh on north facing roofs, where moisture is more plentiful and the algae itself has a chance to grow.

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Why Does Algae Like My Roof?

The shingles in our Raleigh area contain limestone, which is actually pretty great.  It allows your shingles to be heavier, durable and more reflective to shield from heat.  However, roof algae feeds off of limestone, which can eventually weaken your shingles.

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How Does This Affect My House Other Than Looking Bad?

Those pesky algae cells create a dark pigment to protect themselves from the sun.  As this builds up, your roof becomes less reflective and absorbs more sunlight.  This translates into higher AC bills!

In addition, if the algae on your roof is left to grow, it can join forces with a fungus to form lichen.  Moss eventually grows within this teamwork, building up a great layer to absorb seeds from trees or other plants (probably from bird droppings).  Once you start seeing sprouts, it’s way past time for a new roof.

This isn’t something that’s going to happen overnight; more like years.

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How Can I Prevent Roof Algae?

Even though most people call us a “pressure washing” company, we utilize low to no pressure on most surfaces.  Roof cleaning requires no pressure.

Blasting away at the algae will definitely get rid of it, but will more than likely destroy half of your shingle life at the same time.  A low pressure application of specialized roof detergent, along with a rinse or a good rainfall will do the trick.

Special care needs to be taken with plants around your home, since this detergent is rather strong and can kill almost anything green!


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