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  • Josiah Hart

What Causes Black Streaking on Roofs?

Black streaking on older roofs is a common sight throughout the south eastern US. It plagues homeowners with its unsightly appearance, and can cause premature deterioration and granule loss on shingle roofs.


These black roof streaks are typically caused by the growth of algae and photosynthesizing bacteria: specifically Gloeocapsa magma. This bacteria thrives in warm, humid climates and is usually found growing on the north-facing slopes of roofs and areas that receive less sunlight. The black streaks themselves are the result of the bacteria's pigmentation, which is a dark color and helps it to absorb sunlight more effectively. As the bacteria continues to grow and spread, the black streaks become more pronounced and can cover a large portion of the roof. Gloeocapsa magma photosynthesizes and breaks down the limestone in your shingles as it grows, spreading across the roof and causing premature shingle deterioration and loss of shingle granules, putting extra strain on your home's gutter system and reducing your roof's lifespan.


So how do you get rid of it? Gloeocapsa magma is organic growth just like algae or mildew. This means that a specifically formulated roof soft wash can resolve the issue safely and effectively. Depending on the severity of the Gloeocapsa magma staining, the pitch of your roof, and the condition of your shingles, we adjust our chemical ratios to formulate a solution capable of instantly neutralizing the Gloeocapsa magma on your roof. After the chemical wash has been applied, we let it dwell to ensure the bacteria is killed to the root. The chemical will continue to actively kill bacteria for up to 12 hours after application and will break down into salt and water after it's completed its job. Any staining will wash away with the next rain and the chemical breakdown means that your lawn will stay happy and healthy! But don't take our word for it, a chemical soft wash is the number one recommendation for resolving roof stains from the biggest shingle manufacturers.


As a final note, never ever use pressure to clean your roof. Doing so will cause granule loss, void your roof's warranty, and could cause water ingress. Pressure washing may remove surface level stains, but bacteria growth under the shingle surface will ensure the stains quickly return. If you'd like to learn more about roof cleaning, feel free to call our office number. We'd love to talk!


A no pressure roof wash can make your roof look brand new!
A no pressure roof wash can make your roof look brand new!

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