Why Are There Black Marks On My Roof

The black streaks running down roofs are actually a hardy algae called gloeocapsa magma.

Why are there black marks on my roof.

Technically the black streaks on roofs are a form of algae known as gloeocapsa magma. While the streaks do not cause a great deal of damage they can cause the shingle to age prematurely. Why black streaks moss and fungus grow on roofs. This algae growth usually begins as small spots and then eventually becomes visible streaks.

The black streaks are also known as black algae or roof mold. It appears in streaks or patches of slime that can be anywhere from blue green to dark black. Although it may look like mold or fungi these unsightly black streaks or smear like stains may indicate a type of roof algae known in technical terms as gloeocaspa magma. The black roof stains are caused by a form of algae that has been around for years typically found in the woods on the north side of trees or on exposed rocks.

Across the entire eastern half of the country roof shingles tend to grow a species of algae called gloeocapsa magma. Although these dark spots and ugly black streaks on your roof may look like dirt mildew soot or mold what they really are is algae. The remedies for and means of preventing stains on roof shingles are discussed as well. If you live in a humid area of the country you ve probably seen unsightly dark streaks on asphalt shingle roofs.

As the blue green algae accumulate they develop a dark hardened outer coating which results in the black stains you see. Roof algae rarely poses a threat to the health of the roof. The algae will worsen and become more noticeable each year trapping moisture and causing premature shingle aging and granule loss. Roof experts tell our researchers that though other components are being added to shingles to hinder algae growth they still get calls to deal with black marks on relatively new roofs.

Over time this algae accumulates developing a black outer coating which causes stains on roof shingles. Black marks became a problem about 20 years ago when manufacturers began adding limestone granules to add weight to material used to coat shingles. Green or black algae stains. Dark black or brown roof shingle stains are often caused by black algae bleed through or extractive bleeding of asphalt dirt soot or organic debris.

But now this black algae is termed a roof shingle algae because of the annoying discoloration on a asphalt shingle roof. Photo courtesy of angie s list member paul r. The most common type is known as gloeocapsa magma also known as blue green algae. Here s why algae grows on roofs.

But there are other roof stain colors and causes. Dark streaks or splotches on your roof could be caused by bacteria and commonly occur on the north side or shaded area of the roof. The algae feed on the limestone in shingles.