What’s eating your roof?

Mimi Vanderhaven • July 1, 2026

Those unsightly black streaks on the roofs of area homes (maybe even yours) are not mildew. They are airborne bacteria. Here’s why the colony is dangerous—and how to get rid of it.

A stack of books sits on a wooden table, next to a lit candle and a warm cup of coffee or tea.

The telltale black streaks on roofs are actually Gloeocapsa magma—bacteria that feed on the limestone in your shingles, shortening your roof’s lifespan.


One of the most prominent eyesores on homes in Northeast Ohio is the black streaks on so many rooftops. These curb-appeal-killing streaks are not mildew. They are caused by airborne bacteria called Gloeocapsa magma, which first appeared in the Southeast and has since spread throughout most of the rest of the United States and Canada.


One reason for the spread of the bacterium is the increased use of limestone filler in the manufacture of asphalt shingles since the 1980s. Limestone not only holds moisture but is also calcium carbonate, the natural food of Gloeocapsa magma.


It is literally eating your shingles.


These bacteria can cause significant damage to roofs, including shingle decay and reduced reflectivity. Over time, Gloeocapsa magma breaks down the shingles, decreasing the roof’s ability to reflect ultraviolet radiation and shortening the roof’s lifespan.


“Once the bacteria become noticeable, the stains continue to worsen year after year if left untreated,” explains Ken Wilson, founder of Pristine Clean, the popular, locally owned power-washing company. “As the colony grows, it is pulled downward by gravity, creating the black streaks on roofs you now see everywhere.”


Protect Your Homeowners Insurance

Insurance companies are so concerned about Gloeocapsa magma many are now using overhead Google images to identify roofs with the telltale black streaks and cancel home insurance policies unless the roofs are cleaned. It’s now common for homeowners to receive a letter from their insurance company featuring an overhead image of their house and a threat to cancel their policy.


And because Gloeocapsa magma is an airborne bacterium, it can spread from house to house throughout a neighborhood.


These concerns—combined with the sheer unattractiveness of the roof stains—are a good reason to have your roof cleaned.


Safe, Effective Cleaning

“We’ve been fighting Gloeocapsa magma for years,” Ken says. “Over that time, we’ve developed an antibacterial soft-wash system that removes black streaks and eliminates the bacteria without damaging your roof. It’s become one of our most popular services.”

Pristine Clean’s technicians receive classroom and in-the-field training, along with an apprenticeship program, to ensure the safety and effectiveness of every job.


In addition to simply cleaning your shingles, Pristine Clean can extend the life of your roof up to 15 years with “Roof Renew,” an eco-friendly, soy-based application service that restores suppleness to your shingles, reducing cracking, breakage and granular loss. 


Siding and Concrete, Too

In addition to roof cleaning, Pristine cleans and seals siding and concrete surfaces, including driveways, patios and sidewalks. “There is still plenty of summer left and time to enjoy your patio and backyard,” Ken adds. “Removing grime, mold and mildew dramatically enhances the enjoyment of your outdoor activities.”


In just a few weeks, we’ll hear the rumble of school buses and the whistle of referees as preseason football begins. That means now is also a good time to schedule Pristine’s Concrete Clean & Seal to protect your driveway from Northeast Ohio’s damaging freeze-thaw cycle.


Fair Pricing

Unlike some home improvement companies that charge as much as they think they can, Pristine’s pricing is based exclusively on the square footage of your job. “By looking at an image of your home online, we can give you a quote right over the phone,” Ken says. “You pay what your neighbors pay.”


Pristine Clean Power Washing

Serving all of Northeast Ohio

440-454-7041

PristineClean.com

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    Pristine Clean’s technicians use an antibacterial soft-wash system to safely remove black streaks and eliminate the bacteria.

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  • Slide title

    Over time, Gloeocapsa magma breaks down the shingles.

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    Ken Wilson, founder, Pristine Clean

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Save 10% Today!


Right now, Pristine Clean is offering 10% off four big services: House Wash, Concrete Wash, Roof Wash, and Roof Renew. Offer good through August 15, 2026. Call 440-454-7041 for a quick, over-the-phone quote or visit PristineClean.com.

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