Black Streaks on Roof and Green Stuff on Siding

Black Streaks on Roof and Green Stuff on Siding

Black Streaks on Roof

Let’s start with the black streaks on your roof. These unsightly marks are actually layers of microorganisms. In the first few years after your roof is installed, you might not notice anything unusual. However, between 4 and 7 years, streaks often begin to appear, typically on the north-facing side of your roof. By years 7 to 12, the streaks may spread across your entire roof.

The good news? These streaks can be professionally removed by a roof cleaning service, like Outdoor ProWash LLC in Nashville, TN. And no, having black streaks doesn’t necessarily mean your shingles need replacement—though by 12 to 15 years, that might be a consideration.

These microorganisms trap moisture, creating a welcoming environment for other organisms to thrive. Over time, this growth can form root-like structures that penetrate the shingles, loosening granules. While this might slightly reduce the lifespan of your roof, most homeowners are more concerned about the streaks’ unattractive appearance. If you’re reading this, chances are you just want the streaks gone!

What Causes Black Streaks on Roofs?

The culprits are heat, moisture, and nutrition. This combination creates the perfect environment for growth. In some cases, these organisms even feed on the materials in your roofing (learn more about roofing materials).

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Green Stuff on Siding

If you live in the South, you’ve probably seen the green stuff growing on siding—and maybe even on your own home. This growth isn’t picky; it can spread across fascia, trim, vinyl windows, and even gutters, where it appears black or spotty. It’s particularly heavy on the front of gutters and in shaded areas.

This “green stuff†is a mix of microorganisms that thrive on almost any surface. Vinyl siding is especially vulnerable during certain times of the year, when dew forms much like condensation on a cold glass. This moisture, combined with lingering dust on the surface, provides the perfect conditions for airborne spores to grow.

While brick siding is less prone to this type of growth, it can still occur in areas exposed to constant moisture—like near overflowing gutters, at the ground level in damp areas, or on horizontal surfaces where water collects.

What Causes Green Stuff on Siding?

The same trio of heat, moisture, and nutrition allows green stuff to flourish. In this case, “nutrition†often comes from dirt, hydrocarbons, or even aging paint. Over time, the biocides in paint wear off, and some of its ingredients can even become a food source.

This green growth—often referred to as mildew—commonly forms near dryer vents or on the north side of houses, where conditions are ideal for its spread.

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Want to Get Rid of It?

Professional cleaning services can effectively remove black streaks from your roof and green stuff from your siding, restoring your home’s curb appeal. Visit Roof Cleaning in Nashville TN to learn more about our services and how we can help!

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