What Are the Black Streaks on My Roof?

For maintenance-conscious homeowners, few things are more frustrating than the unsightly black streaks that often appear on aging roofs.

They’re high and out of reach. They seem to show up out of the blue. And they can create a fair bit of worry. If you’re in this position, you’ve likely asked yourself some of the following fretful questions.

What are these black streaks?

Believe it or not, these streaks are from a growth that’s scientifically named gloeocapsa magma. Because the original growth is green, many people refer to it as a type of algae. However, it’s actually a species of bacteria.

Homeowners often don’t notice this growth until the black streaks have started to appear on the roof. By this time, the growth has developed a durable, UV-resistant coating (hence the dark colour).

How did these bacteria get on my roof?

It’s pretty much impossible to keep these spores from appearing on your roof. Since they’re airborne, they travel through the wind and find their way to hospitable environments. They can also be carried by birds and other wildlife that make pitstops on the top of your home.

These bacteria spores prosper in locations that are dark and have an abundance of moisture. So, if you live in a humid environment – like Greater Vancouver – your home is a prime target. They especially love the North-facing sections of your roof, where they can avoid direct sunlight.

Why do they like my asphalt shingles?

The unfortunate truth is that your asphalt shingles often contain crushed limestone, which is one of these bacteria’s preferred meals. So, once they end up on your roof, these spores discover that you’ve laid out an all-you-can-eat buffet for them.

From here, the growth can eat and relax. Left unimpeded, the colony will creep down your roof, growing downward thanks to the pull of gravity. Over time, it will also deteriorate your shingles, lessening their reflectivity and shortening their service life.

Can I get rid of this growth and keep it from showing up again?

The good news is that these stains are not permanent. They can be addressed and removed with chemical sterilization treatments. These formulas are designed to kill the growth you can see as well as any hidden spores that might try to hide away underneath your shingles.

Once the stains are gone, you can also take extra measures to keep new bacteria from moving in. Roofing contractors install preventative metal strips (often zinc strips or copper) underneath the top of roof shingles. As rainwater washes over the strips, it distributes toxins from the metals that will kill any new spores without damaging your roof or the surrounding environment.

Should I hire professionals to clean my roof?

We’ll answer your question with a question: do you want to climb up on your roof and risk damaging your shingles?

For most, the answer is an immediate “No!”

At West Coast Moss Removal, we’re proud of our trained, professional team. We show up to every project with the equipment, experience, and expertise to remove these bacteria without damaging your roof. Reach out and book your roof cleaning service today.