BLACK STREAKS ON YOUR ROOF
It’s Not Dirt –It’s Alive!
It’s algae, a type of cyanobacteria, and it feeds on the limestone in asphalt shingles. As it eats your shingles it grows, forming a dark protective coating that absorbs sunlight, increases roof temperatures, keeping moisture on the roof surface longer, and creating conditions that encourage moss growth, and deterioration.
Black algae often begins on the north-facing or shaded sections of a roof where moisture lingers. The spores are spread by wind, so once one home in an area has algae, neighbouring roofs can gradually become affected as well. That’s why entire lakeside neighbourhoods often develop similar black streaking over time.