During the last few years, we’ve noticed an increasing number of roofs streaked with unsightly black stains. You’ve probably noticed them to, and because of our expertise in roofing, we often field questions about what causes these stains and whether the pose a threat to the roof or people living in the house. Invariably, we’re also asked how to get rid of them. Here are the answers to those questions.
What are the stains?
The black stains are plantlike bacteria growing on your roof. The scientific name for the bacteria is Gloeocapsa Magma, and they’re taking advantage of a new ingredient common asphalt shingles. These shingles employ limestone as a filler, and limestone provides the water and organic material the bacteria need to grow and reproduce. Rising temperatures and humidity certainly don’t hurt their spread, but shingles made with limestone are the main culprit.
What harm can the stains do?
A lack of scientific research makes this a bit of a gray area. Here’s what we do know: these bacteria collect moisture and consume organic material, which can speed up the aging and deterioration of the roof. Venturing further a field, we also know another organism that thrives on moisture and organic material: mold. Mold can live off the tar on your roof or even the bacteria themselves. Once mold enters the picture, we need to start talking about the health of people in and around the house, because mold can be toxic.
How can I get rid of the stains?
The good news is that removing the stains can be relatively easy. Allied Remodeling offers non-pressure stain removal through its sister company Advanced Roof Restoration. Visit www.advancedroofrestoration.com to learn more or contact Allied Remodeling at 410-769-9700 to schedule a free estimate.

