What Causes Streaks on Roofs?

 

As home inspectors, we are often faced with the question from a potential home buyer about what the ugly black streaks on a roof are, and more importantly how do they get rid of them?

Many people believe the streaks are caused by dirt or pollen building up on the roof, but more often than not the culprit is actually an algae that is growing on the roof and feeding off the roof materials.

The algae is most commonly Gloeocapsa Magma, a blue-green algae that travels and propagates through airborne spores.

The algae doesn’t typically do much damage to the roof, but it does look unsightly. And many people argue as to how to deal with it. Continue reading “What Causes Streaks on Roofs?”