Those dark streaks running down your roof aren’t dirt — it’s algae (the scientific name is Gloeocapsa magma), and Georgia’s humidity makes it one of the most common calls we get. It won’t cause your roof to fail overnight, but it means moisture is sitting on those shingles longer than it should, and that shortens their life.
Pressure washing helps short-term, but most people don’t know this: too much force strips the protective granules right off the shingle, which speeds up wear and can void your manufacturer warranty. If you’re replacing a roof anyway, ask about algae-resistant shingles — they use copper granules that keep streaks from coming back for years, not just months.
If your roof is past 10-12 years old and covered in streaks, don’t just wash it and hope — get a real inspection. We’ll tell you straight whether it’s cosmetic or something worth watching.