Those Black Streaks Are Algae
The dark streaks running down your shingles are roof algae — organic growth that feeds on the limestone filler in asphalt shingles. It starts on the north-facing and shaded slopes, where the roof stays damp longer, and it spreads over time. Beyond curb appeal, heavy growth traps moisture against the roof surface.
Soft wash roof cleaning treats the algae with a low-pressure application and a treatment mix designed for organic growth, then rinses clean. The streaks wash away and the growth is killed at the root, so the roof dries to its normal color.
Why Soft Wash Instead of Pressure for Shingles
A pressure washer can blast streaks off a roof — and take protective granules, shingle edges, and warranty coverage with them. Asphalt shingles are built to shed water, not to take a high-pressure jet. Force can lift granules, break seals between shingles, and drive water underneath the roof surface.
- Low pressure — about garden-hose strength, not a pressure jet
- Kills algae and mildew rather than just rinsing the surface
- Safe for asphalt shingles and most roofing surfaces
- Results last longer because the growth is dead, not just hidden
Our Roof Soft Wash Process
- Inspect — We walk the roof visually for shingle condition, flashing, and problem growth areas.
- Protect — Landscaping and plants get rinsed and covered where needed before we apply anything.
- Treat — Low-pressure application of the soft wash mix, with dwell time to kill algae and mildew.
- Rinse — Gentle rinse washes the streaks away and finishes the clean, with cleanup before we leave.
Roof soft wash pairs naturally with a full house washing — one visit, one scheduling call, whole exterior covered.
Frequently Asked Questions
What are the black streaks on my roof?
Those dark streaks are usually roof algae — an organic growth that feeds on the limestone filler in asphalt shingles. It shows up most on north-facing and shaded roof slopes and spreads over time if left alone.
Is roof soft washing safe for asphalt shingles?
Yes. Roof soft washing uses low pressure — about garden-hose strength — plus a treatment mix that kills algae and mildew at the root. It does not lift granules or break shingle seals the way high-pressure washing can.
How long does a roof soft wash last?
Because soft washing kills the growth rather than just rinsing it off, results typically last a year or more. Shade and tree cover affect how quickly streaks return.
How much does roof soft washing cost?
Cost depends on roof size, pitch, and how much algae is present. Call (423) 556-9801 for pricing — many homeowners pair a roof soft wash with a full house wash in the same visit.
More on the method: soft washing.
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