What type of algae growth is commonly found on roofs?

Algae that holds moisture and causes rot is a significant concern for roofing systems. This type of algae, often referred to as Gloeocapsa magma, typically appears as dark stains on roofs, particularly on asphalt shingles. These algae thrive in moist environments and can retain moisture on the roof surface, which in turn creates an environment conducive to the growth of other harmful organisms, such as mold and moss.

The presence of this algae can lead to the deterioration of roofing materials over time. Its ability to hold moisture can make shingles brittle, leading to damage and reducing their lifespan. It can also contribute to rot in the underlying roofing structure, which poses a risk to the integrity of the entire roofing system. This is why it's important for roofing contractors to take preventive measures, such as installing algae-resistant shingles or maintaining proper roof drainage, to minimize algae growth and its associated risks.