Roof cleaning that does not wreck your shingles
Low-pressure soft washing kills the algae causing black streaks without stripping the granules off your roof. Get quotes from contractors who do it properly.
Never let anyone pressure wash a shingle roof
High pressure strips the granules off asphalt shingles. Those granules are the roof's UV protection. A roof that is blasted clean can lose years of life in an afternoon, and it usually voids the shingle warranty.
The correct method is a low-pressure soft wash with a cleaning solution that kills the algae at the root. It looks less dramatic on the day and it is the only method most manufacturers and roofing associations endorse.
- Ask directly: “Do you soft wash or pressure wash roofs?”
- If the answer involves pressure, stop there
- Ask how they protect gutters, plants and the drive-off area
Typical roof cleaning pricing
| Roof | Typical range |
|---|---|
| Single-story, simple pitch | $400–$650 |
| Two-story or complex pitch | $600–$1,100 |
| Metal roof | $350–$800 |
| Tile roof | $600–$1,400 |
Steep pitch, height and access all move the price. Quotes come from the contractor.
Those black streaks
They are a living organism — gloeocapsa magma, a blue-green algae that feeds on the limestone filler in shingles. Scrubbing does not stop it. It has to be killed.
How long it lasts
A proper soft wash typically holds for three to five years. Shaded, damp and north-facing roofs return faster.
Cheaper than a roof
Algae shortens shingle life. Cleaning at a few hundred dollars every few years is considerably cheaper than replacing a roof early.
Roof cleaning questions
Is roof cleaning safe for my shingles?
Soft washing is. Pressure washing is not — it strips protective granules and can void your shingle warranty. Always confirm which method the contractor uses.
What are the black streaks on my roof?
An algae called gloeocapsa magma. It feeds on limestone filler in asphalt shingles and spreads in humid, shaded conditions. It has to be killed chemically, not scrubbed off.
Will it hurt my gutters, plants or driveway?
Not if the contractor pre-wets and rinses landscaping and controls runoff. That is a standard part of the job for anyone who does this properly.
How often does a roof need cleaning?
Every three to five years for most homes. Heavily shaded roofs in humid climates may want it more often.
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