Black Streaks on Roof Shingles? Here’s What to Do

Have you noticed black streaks on roof materials or patches along your rooftop, especially in the shade? Roof shingles often fade into lighter colors over time, but sometimes the opposite effect can occur thanks to subtle plant growth. Fortunately, there are ways of removing those black patches.

Black streaks: Blame the algae

Those black streaks on your shingles may look like problems with old age or damage, but they are really caused by algae – specifically, gloeocaspa magma is usually to blame for those wavy, dark shades that grow as the algae bloom spreads.

Many homeowners are surprised to find that algae is growing on their rooftop, because algae is usually associated with pools and seashores. However, given the right conditions it can also flourish on shingles: Those conditions include plenty of moisture or humidity (homes in the central United States do not suffer from this problem), and the right kind of minerals for the algae to feed on.

So, how do you know if those black streaks on roof shingles are indeed algae, or a different problem? One of the best signs is how the algae behaves around metal. If you have metal vents, chimneys, or metal flashing along your roof, take a look: Do the black streaks die out around and underneath those metal pieces? During rainfall, elemental traces of zinc and copper often leak down from metal through your shingles. These traces are poisonous to algae, which will avoid these sections of your roof.

Getting rid of the algae

Yes, you can get rid of those black streaks on roof shingles, but it will require a powerful chemical cleaning. Contact local roofing professionals and ask them about chemical cleanings. Not only do professionals have power-wash tools to make cleaning effective and safe for your shingles, but they will also know what chemical solutions to use. Regulations may prevent the use of certain chemicals in your area – also, some algae-killing chemicals are also poisonous to the plants and shrubs around the edges of your house, so avoiding these pitfalls is key.

Algae-resistant materials

Chemical washes can kill the current crop of algae, but algae can grow back over time, so it’s a temporary solution. However, if you are considering replacing your shingles or doing other roof repair, ask your roofer about shingles that resist algae growth. Current products on the market include shingles that have algae-fighting granules built in to fight this problem. If you do not want to replace your shingles, then consider installing zinc or copper strips along your roof ridges, a simple procedure that discourages algae from growing all along your roof.

Photo Source: Flickr