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What are those black streaks running down my roof?

WHAT are they?

The black streaks you see running down your roof are a hardened form of algae known as, gloeocapsa magma. Overtime these blue-green algae will begin to harden on your shingle, taking on a much darker color and causing more than just an eye-soar from the ground level.


WHY is it growing on my roof?

The algae you see up there is actually feeding on your roof. Composition shingles consist of a variety of different "fillers". One of the most abundant fillers in the shingle is, limestone. Shingle manufacturers have been using limestone as a predominant filler for decades due to its attractive cost and abundance of supply. Although the limestone will fight back and eat away at the blue-green algae, it will never win the war. As the algae begins to harden on your roof surface, the limestone inside of the shingle becomes defeated.


DO I need a new roof?

If your home has fallen victim to the gloeocapsa magma, you are not alone. Most roofs over the age of 10 will start to show signs of algae growth, and it will continue to spread over time. You may be thinking, my roof still has 5,10 or even, 15 years left in it, unfortunately this might not be the case. Keep in mind, the algae are slowly eating away at the shingle which can significantly decrease its lifespan.


If the streaking on your roof is abundant or if you are getting ready to sell your home, it would be a good idea to replace the roof. An abundance of streaking likely means that the algae has been eating away at the shingle for many years, making the existing roof structure much weaker than it has been before. Not only does the abundance of black streaking make your roof weaker, but it also provides a potential buyer (if you are planning to sell your home) a bargaining chip at the table. Realtors will coach their clients to look at the roof before they look at anything else on the home, as they know that this is a large expense their buyer will incur.


HOW can I keep the black streaks away?

  • Consider purchasing an ALGAE RESISTANT shingle for your next roof

  • Install copper or zinc strips on your next roof

  • Mixture of TSP, Bleach and Water can temporarily remove staining (do not scrub excessively)







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