What are the black spots on my roof? Black markings are a well-known occurrence that many homeowners have had to deal with. Let’s look at some of the potential causes of dark spots on the roof, including the most common.

Most Dark Spots on Roofs Are Algae

In most cases, algae are responsible for the dark spots and streaks — more specifically, algae called Gloeocapsa magma. These blue, green, and black-colored algae grow more easily in moist conditions, making their presence more common on homes built in warm and humid climates. Additionally, you’re more likely to find the black algae growing in dark locations, such as parts of the roof shaded by trees or on the north side of the roof that has less exposure to sunlight.

Gloeocapsa magma starts out as smaller spots that grow into the more familiar black stains over the course of two months or more. This alga shields itself from the UV rays of the sun by creating a hardened coat with a dark pigment — resulting in its well-known color. The streaking occurs because of gravity, as the algae spots are gradually pulled down the roof over time and stretch out.

Although algae can grow on many different kinds of roofing, it is found more often on asphalt roof shingles. Just like all other organisms, algae need to eat food to sustain themselves and survive — and the limestone in asphalt shingles just so happens to be its favorite food. As the algae feeds off of the limestone, it continually weakens the shingles and causes them to age prematurely. In addition, the longer algae remains on your roof, the bigger it will grow and the worse its effects will become. With that in mind, it’s best to remove dark spots on the roof as soon as you can to prevent them from becoming any larger.

What Are the Black Streaks on My Roof If They’re Not Algae?

While Gloeocapsa magma is a common culprit of dark spots on your roof, it is not the only possibility. There are other causes of black roof streaks that homeowners should be wary of, including:

Mold and Mildew

Just like with algae, mold and mildew grow more readily in moist conditions. Not only are their black spots unappealing, but their dampness will result in roof rot. As a result, it’s best to get mold and mildew off your roof as soon as you can. A professional cleaning company like Poseidon Power Washing can make quick work of removing unattractive mold and mildew from roof surfaces.

However, it’s worth noting that the growth of mold and mildew can occur because of algae. Algae is the first stage of growth that can lead to numerous other organisms including lichens, which indicate a serious infestation you will want addressed immediately.

Accumulated Debris

If the dark spots on the roof aren’t algae or mildew, then they might just be built-up debris. The roof can collect a lot of dirt, branches, leaves, and other forms of debris over time, which can build up near the gutters and cause damage. Unlike algae, homeowners can clean away dirt and leaves more easily.

Do You Have Black Spots on Your Roof? Contact Us Today!

Whether you have black spots on the roof or stains on your concrete driveway, the team at Poseidon Power Washing will be happy to help. We offer various cleaning assistance, including our dumpster pad cleaning service, gas station cleaning services, and many more. For more information and to schedule an appointment, give us a call today!

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