Why Georgia Humidity Causes Black Roof Streaks
Georgia summers are brutal. The heat stays. The humidity stays. And apparently, so does something called Gloeocapsa magma. That is the blue-green algae behind every black streak running down your roof right now.
It feeds on the limestone filler inside asphalt shingles. Warm air and moisture give it exactly what it needs to multiply fast. Georgia just happens to be a five-star resort for this stuff.
To survive intense sun and UV rays, Gloeocapsa magma builds a dark pigmented outer shell for protection. That shell is what you are seeing. Not grime. Not pollution. A living organism doing its thing on your shingles.
Left untreated, those streaks can shave five to ten years off your roof's lifespan. The algae acts like a moisture sponge, keeping shingles damp long after rain stops.
The good news is it is cleanable. The better news is it is preventable. Algae-resistant shingles with copper or zinc granules are now widely available and they work.
Your roof is not aging badly. It just needs the right attention before Georgia's humidity wins.