Ever wonder what those black streaks on the roofs of thousands of homes are? Those stains are not mold, but the result of an algae known as gloeocapsa magma, which thrives in areas where the summer climate is hot and humid. This algae proliferates everywhere in the U.S. except for western states where the climate is less humid. The first stains usually appear on the north-facing sides of a roof, which receives less light. Algae travel through the air, so if one neighbor receives a few spores, the whole neighborhood will soon be sporting the black streaks.
The issues caused by gloeocapsa magma go beyond aesthetics, although that alone is an important reason for having it removed. Neighbors and potential home buyers are finding the growing masses of black streaks to be so unsightly that they focus their attention on your roof instead of on the rest of your property’s beautiful exterior. But the physical damage starts with the style of shingles that have become popular in the last 20 years and are likely on your own house. When the algae settle in moist areas on a roof, they feed on microorganisms in the moisture. When that food supply is gone, they begin to feed on what remains causing premature aging, rotting and the destruction of the limestone component of your roof.
Unfortunately, not even a heavy thunderstorm can wash away gloeocapsa magma. In fact, rain makes it worse by adding additional moisture to the colony and by spreading it as the rainwater flows down your roof. That’s why even on highly infected rooftops you often see clean spots in front of dormers where the water does not flow.
Instead, it’s important to have these nasty invaders killed and your roof cleaned periodically. Have your roof cleaned and disinfected by a professional. They will soft clean and remove the stains, then follow up with a proprietary system that kills the algae and prevents its regrowth. This highly economical occasional investment is far less expensive than replacing your roof.