Black streaks on asphalt roofs are caused by blue-green algae (Gloeocapsa magma). In this blog, Residential Concerns shares an in-depth look at what blue-green algae is, how to rid your residential roofing system it and how to make sure it never returns.
Algae metabolize sunlight through photosynthesis and can subsist on water alone for long periods of time. Blue-green algae is a common species that thrives on open-air surfaces such as rooftops. Its dark, outer “skin” protects it from ultraviolet (UV) rays and heat from the sun and is what causes the black streaks you see on the roof.
Blue-green algae subsist on the limestone content of asphalt shingle granules, but it does not cause any real damage. Still, its unsightly appearance is an eyesore that can drag down your home’s curb appeal.
Fortunately, you have several options when it comes to removing the algae:
Professional Cleaning — Hire a roofer that offers cleaning and maintenance services. This is the safest option for most homeowners. With an experienced roofing contractor, you won’t have to worry about damaging the roof or voiding the roofing warranty.
Spray the Roof With a Cleaning Solution — You can spray the roof with an off-the-shelf algae remover. You’ll need to measure the roof area first to determine how much you should purchase. You can also use a 1:1 bleach and water solution.
Pressure Washer — Using a pressure washer isn’t generally recommended for roofs. If you must use it, make sure you are using nozzles with medium to low force.
Install Zinc Strips — You can purchase zinc strips that are designed to be installed at the roof ridge. The strips disperse zinc particles onto the roofing surface when it rains. You can have zinc strips installed on a new roof as a preventive measure.
Roofing manufacturer GAF offers a preventive solution to blue-green algae: StainGuard Plus™ Shingles. Algae-fighting copper capsules are blended with the roofing granules. StainGuard Plus Shingles also feature a proprietary time-release technology, which releases copper particles gradually and consistently throughout the roof’s service life.
Residential Concerns is your leading provider of roofing services, including roof inspection and repairs. Give us a call at (770) 304-1311 or fill out our contact form. We serve homeowners in near Sharpsburg, GA.
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