Roof cleaning cost in 2026, and what those black streaks on your roof are
What a soft-wash roof cleaning costs on three roof sizes, what causes black streaks and moss, why shingles should never be pressure washed, and how often a roof needs cleaning.
The black streaks running down so many roofs are not dirt. They are algae, and the wrong way of removing them shortens the roof's life. Here is what causes them, what a proper roof cleaning costs, and how long it lasts.
What the streaks and the green are
- Black streaks: usually an algae called Gloeocapsa magma. It spreads from roof to roof in warm, humid weather and does best on the north side and under trees. At first it is cosmetic.
- Moss: grows on shaded roofs that stay damp. It holds water against the shingles and can lift their edges, which is where leaks start.
- Lichen: crusty grey-green patches that grip the surface hard. It needs a treatment and time to die off, not scrubbing.
What roof cleaning costs
| Type | 1,200 sq ft house | 1,800 sq ft house | 2,600 sq ft house |
|---|---|---|---|
| Soft wash | $619 | $869 | $1,202 |
| Soft wash + moss treatment | $844 | $1,207 | $1,690 |
| Wash + treatment + 2-year warranty | $1,166 | $1,690 | $2,387 |
Priced by the same engine our free quote tool uses, on the roof surface at a 6/12 pitch (about 12% more than the house's footprint). Steeper roofs, three storeys and heavy moss cost more. Cleaning the gutters while the ladders are up is usually a small extra.
How often a roof needs cleaning
- Soft wash alone: streaks typically return in 3–5 years.
- With a moss and algae treatment: 4–6 years.
- To slow it down: trim branches back from the roof so it dries faster, and keep gutters clear. Zinc or copper strips along the ridge release metal ions with each rain that discourage regrowth below them.
Clean it or replace it?
Cleaning fixes the look, not the age. If shingles are curling, cracked, or bald of granules, or the roof is near the end of its life, cleaning it first is money spent twice. Get a free instant roof quote to compare.
Common questions
How much does roof cleaning cost?
About $869 for a soft wash on a typical 1,800 sq ft house, or $1,207 with a moss treatment.
What are the black streaks on my roof?
Usually algae, which spreads in warm, humid weather and on shaded roofs.
Can you pressure wash a roof?
Not a shingle roof: it strips the granules. Roofs are soft washed.
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