What Causes Black Streaks On Roof Shingles

Over time this algae accumulates developing a black outer coating which causes stains on roof shingles.

What causes black streaks on roof shingles.

While the streaks do not cause a great deal of damage they can cause the shingle to age prematurely. Areas of the country with low humidity have fewer instances of roof streaks while the problem is relatively common in the southeast where it s more humid and warm. Black streaks on shingled roofs are a common though mysterious sight. Algae growth may cause discoloration on roofs resulting in brown or black streaks on a rooftop.

Most black streaks form on the northern slopes of roofs where it s darker and wetter ideal for algae growth. Algae growth on asphalt shingles. Algae arrive on the rooftop through the air in the form of spores or clumps of cells. If you re seeing black streaks running along your roof chances are you ve mistaken them for dirt or even mold.

The most common type is known as gloeocapsa magma also known as blue green algae. 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. Black streaking on roofs is a common problem. Why are there dark streaks on my roof.

Algae may be mistaken for soot dirt or tree droppings most of which typically produce only localized discoloration. This algae growth usually begins as small spots and then eventually becomes visible streaks. The streaks are caused by a type of algae known as gloeocapsa magma. While not immediately damaging they can prematurely age shingles.

Here s what they are and what to do about them.