How to Get Rid of Roof Algae & Black Streaks in Florida

If your Florida roof has dark streaks running down it, you don't have dirt or "aging shingles." You have a living organism — and Florida is its favorite place on earth.

What those black streaks actually are

The streaks are a blue-green algae called Gloeocapsa magma. It feeds on the limestone filler in asphalt shingles and the moisture our climate provides in abundance. Heat, humidity, and afternoon rain make Central Florida a perfect breeding ground — which is why nearly every untreated roof here eventually streaks.

Why it's more than just ugly

Algae holds moisture against your roof and slowly breaks down shingles, shortening their life. Left alone it spreads, and on the north and shaded sides it invites moss and lichen, which are even more destructive. So it's not only curb appeal — it's protecting the roof you paid for.

What NOT to do

• Don't pressure wash it. High pressure strips the protective granules off shingles, can crack tile, and voids many warranties.
• Don't scrub or use bleach randomly. The wrong mix and method damages landscaping and doesn't kill the algae at the root, so it returns fast.
• Don't ignore it. It only spreads and gets more expensive to deal with.

The right way: soft washing

The industry-correct method is soft washing — low pressure plus a roof-safe solution that kills the algae at the root. Because the organism is actually killed (not just rinsed off the surface), a proper soft wash keeps streaks gone for years, not weeks. It's safe for tile, shingle and metal, and it won't harm your warranty.

How to keep it from coming back

Trim back overhanging branches for more sun and airflow, keep gutters clear, and have the roof soft washed when streaks start to reappear. In our climate, a gentle wash every year or two keeps algae from ever getting a foothold.

Seeing streaks now? Send us your address and we'll fly a drone over the roof and get you a free quote — no obligation.