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Does your roof have ugly black streaks?  Wonder what is going on?  The culprit is gloeocapsa magma, also known as roof algae.  This occurs in all but the driest climates, but especially thrives in warm, humid climate we have here in Northeast Florida.  It spreads through airborne spores and animals.  While the algae can grow on all roof types (tile, metal, wood shakes) it particularly thrives on asphalt shingles.  Gloeocapsa magma uses the limestone filler used in shingles as a nutrient to support growth.  Like moss on the trunk of a tree, roof algae normally starts on North side of your roof that receives the least amount of sun.  To learn more about the biology of gloecapsa magma click here. 

What can you do?  First thing you can do it keep your roof as dry as possible and exposed to as much sun as possible.  Have a licensed tree service trim any trim any limbs overhanging your roof, keep your roof clear of any dead leaves and pine needles, and your gutters clean and draining.  While these steps will not eliminate the bacterium, they will help slow its growth. 

According to the Asphalt Roofing Manufactures Association, the best way to kill the glaecapsa magma is a roof soft wash with sodium hypochlorite, the active ingredient in bleach.  While home improvement stores sell roof cleaning solutions, we have seen any on the market strong enough to effectively solve the problem.  Clean Slate ProWash recommends a 4 to 6% solution of sodium hydrochlorite (SH) applied directly to the singles.  This can be done with with a pump up garden spray filled with 50% water, 50% liquid pool chlorine (10% to 12.5% SH), and a splash of liquid laundry detergent as a surfactant and letting it dwell.  The cleaning solution will kill the actively growth and remove the resulting black stains.  We do not recommend rinsing.  The stains will turn brown and will come down with the next rain storm. Any areas that are still black will need to be retreated (if it's brown, it's coming down, if it's black, your going back.).

***Please note, ladders can be dangerous.  Proper precautions need to be taken before accessing your roof.  10% to 12% concentrated sodium hydrochlorite is a strong caustic solution and proper care and PPE should be used (eye protection, long sleeves and pants, chemical resistant gloves, eye protection and respirator.). Also, a SH solution will make any surface extremely slippery, making accessing the treated roof more dangerous.  Do not walk on treated areas that are still wet.  Please check the manufacturer of your home's specific roofing system before cleaning and always do a test spot.  Always rinse area of the home below roof  and landscaping before, during and after roof wash application.  Strong roof wash solution can kill vegetation, oxidize metals, and discolor certain paint pigments***

Alternatively, you can call a pro like Clean Slate ProWash LLC for a roof wash.  We have low pressure, soft wash equipment specifically designed to safely and effectively clean your roof.   We take all property protection measures to protect your home and landscape from damage while restoring your roof's appearance.  NEVER LET A CONTRACTOR USE A HIGH PRESSURE ON YOUR ROOF.  Pressure washers can cause catastrophic damage to your shingles.  Click here to start an estimate for a roof soft wash estimate from Clean Slate or call us today at 904-860-8760.