Black Streaks & Moss on Your Roof: What They Mean and When to Worry
Quick answer: Dark streaks on asphalt shingles are almost always algae (Gloeocapsa magma), not dirt or mold, and they’re a cosmetic issue — but moss and lichen growing in the same spots trap moisture against shingles and can shorten roof life by years if left untreated. In humid metro Atlanta, algae streaking typically appears within…