Those black streaks on your roof are alive.
Why Central Florida roofs get black streaks (Gloeocapsa magma algae), what it does to shingles, why pressure washing makes it worse, and how a soft wash removes it for 18 to 24 months. · 5 minute read
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What the streaks actually are
The dark stripes running down shingle roofs across Longwood, Lake Mary, Orlando and the rest of Central Florida are not dirt, soot or tar bleeding out of the shingle. They are a colony of Gloeocapsa magma, a blue green bacteria that feeds on the crushed limestone used as filler in asphalt shingles. It builds a dark protective coating to survive the sun, which is the black you see. It spreads on the wind, roof to roof, which is why one house on the street gets it and the rest follow within a couple of seasons.
Why Florida roofs get it so badly
The bacteria wants heat, humidity and moisture that lingers overnight. That describes every night in Central Florida from May to October. North and west facing slopes dry last in the morning, so they streak first. Homes under oak canopy in Casselberry, Winter Park or Tuscawilla streak faster than homes on open lots in newer communities, but every roof gets there eventually.
What it does to the roof
The colony holds moisture against the shingle and slowly eats the limestone filler. Over years that loosens granules and shortens the useful life of the roof. It is also the number one reason HOAs in Seminole and Orange County send exterior violation letters, and insurers and inspectors photograph it during roof inspections. Note what it does not do: there is no credible evidence that roof algae makes the people in the house sick. Anyone selling you a roof wash on a health scare is selling.
Why pressure washing is the wrong tool
A pressure washer blasts the visible streak off the surface and takes shingle granules with it. The bacteria is still in the shingle, so the streaks return in months, and most shingle manufacturers state that high pressure washing can void the warranty. Roofers see the damage from a wand across the shingles all the time.
How soft washing fixes it
Soft washing applies a cleaning solution at roughly garden hose pressure. The solution kills the bacteria at the root and the roof rinses clean with rain and a light rinse. Because the colony is dead rather than scraped, the roof typically stays clean 18 to 24 months in Central Florida. Moss and lichen die on contact but take a few rains to let go, which is normal. We soak plants before, during and after, control runoff, and rinse gutters, walls and the driveway when we finish.
What to expect from a professional roof wash
A quote from a photo or an on site visit, a written guarantee (ours is 12 months on roofs, 24 for Care Plan members), plants protected, before and after photos texted to you, and payment after you have seen the result. If you want a clean roof in Longwood, Lake Mary, Orlando or anywhere in our four counties, text a photo of the roof to (321) 450-4586.
Questions people ask about this.
Can I remove roof streaks myself?
You can buy roof cleaning solutions, but applying them from a ladder on a wet roof is how homeowners get hurt, and the products at the hardware store are weak versions of what professionals use. For a one story roof with a gentle pitch it is possible; for anything else it is not worth the risk.
How much does roof cleaning cost in Central Florida?
It depends on the roof size, pitch, material and how heavy the growth is. Text us a photo and your address and we quote most roofs the same day from the photo and county records.
Will it come back?
Eventually, yes, because the spores are in the air. A soft wash keeps it away for 18 to 24 months; a Care Plan puts the next wash on a schedule at a locked price.
Want us to take a look?
Text a photo of the roof, wall or driveway with your address and we will tell you what it needs and quote it, fast during office hours and always within one business day.