How to Remove Black Streaks From Your Roof in Florida
If your roof has dark streaks running down the shingles, you're not alone — it's one of the most common sights on Florida homes. The good news: those streaks aren't permanent stains, and you don't need a new roof to get rid of them.
What Are the Black Streaks on My Roof?
Those streaks are a blue-green algae called Gloeocapsa magma. It feeds on the limestone filler in asphalt shingles and thrives in Florida's heat and humidity. As colonies grow and die, they leave the dark, streaky stains you see running down the roof — almost always worse on the shaded, north-facing slopes.
Left alone, the algae holds moisture against your shingles, which can shorten roof life and drive up cooling costs as the dark surface absorbs more heat.
Why You Should Never Pressure Wash a Roof
It's tempting to blast the streaks off with a pressure washer — but high pressure tears the protective granules off asphalt shingles, forces water under them, and voids most shingle warranties. The fix becomes more expensive than the problem.
The correct method is soft washing: a low-pressure application of professional cleaning solution that kills the algae at the root. Once it's dead, the streaks rinse away and your roof looks years younger — without any damage.
How Professionals Remove Roof Streaks
1. Soft-wash treatment
A biodegradable cleanser is applied at low pressure, breaking down the algae, mold, and lichen across the entire roof surface.
2. Dwell and rinse
The solution does the work — no scrubbing or blasting. The dead growth lifts away and a gentle rinse leaves the roof clean.
3. Long-lasting results
Because soft washing kills the organism rather than just hiding it, results last far longer than a quick power-blast ever could — typically several years before regrowth.
How Much Does It Cost?
Roof soft washing runs about 25¢ per square foot of roof surface, with a $100 minimum. You can get an exact number in seconds with our estimate calculator, or read our full pressure washing cost guide.
DIY or Hire a Pro?
Roof work means ladders, slick surfaces, and chemicals that need the right mix and handling. For most homeowners it's safer and more cost-effective to hire a professional — see our take on DIY vs. professional cleaning. If you're in Clermont, Winter Garden, or anywhere in Central Florida, we'd be glad to take a look.
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