Service
Black streaks are algae. Pressure is the wrong answer.
Those dark runs down your shingles are a living organism holding moisture against your roof. We treat it chemically, never mechanically.
The black streaking on asphalt shingle is gloeocapsa magma, an algae that feeds on the limestone filler in modern shingles. It holds moisture against the roof deck, and moisture is what shortens a roof’s life. It is not dirt and it will not wash off.
Why pressure destroys a roof
Shingles are protected by a layer of mineral granules. Those granules are what block UV and keep the asphalt underneath from drying out and cracking. Pressure washing strips them. You’ll see them in the gutter afterward. Most shingle manufacturers void the warranty outright if a roof has been pressure washed.
What we do instead
A low-pressure application — under 100 PSI, gentler than rain — of a treatment that kills the algae at the root. It rinses clean and the streaking lifts over the following days as the dead growth washes off naturally. No walking the roof more than necessary, no granule loss, no warranty issue.
How long it lasts
Typically two to three years in this climate before regrowth becomes visible again, depending on tree cover and how much shade the roof gets. North-facing slopes under oaks come back soonest.
Soft wash only
<100 PSI
No granule loss
Warranty-safe
Common questions
Before you book
Will the treatment hurt my landscaping?
Not with proper prep. Everything below the roofline gets watered down and covered before we start, and rinsed after. This is the step that matters most on a roof job because gravity sends everything into your beds.
Why do the streaks take a few days to disappear?
The treatment kills the algae on contact, but the dead growth needs rain and time to release from the shingle surface. Most roofs look dramatically better immediately and fully clear within a week or two.
Can you clean a metal or tile roof?
Yes. Both take a different approach than asphalt shingle, and tile in particular needs care around the underlayment. Send photos and we’ll tell you what it needs.
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What else we clean
Get your free estimate today
Send a few photos and we’ll price it in writing. No site visit needed for most residential jobs.