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Estimate the professional price for soft washing a roof and compare it against doing it yourself. Cost is driven by roof area, pitch, storey height and how heavily algae, moss or lichen has taken hold. Pressure washing strips the ceramic granules that protect asphalt shingles, so the estimate assumes low-pressure soft washing throughout. Read the roof cleaning guide for the method, the solution and the safety gear before deciding which way to go.
Roof cleaning is priced per square foot of roof area, and the two things that move the price are access and how bad the growth is. It is soft washing — a low-pressure chemical process — not pressure washing, which strips the granules off shingles.
| Footprint | 4/12 | 6/12 | 8/12 | 12/12 |
|---|---|---|---|---|
| 1,000 sq ft | 1,054 sq ft | 1,118 sq ft | 1,202 sq ft | 1,414 sq ft |
| 1,500 sq ft | 1,581 sq ft | 1,677 sq ft | 1,803 sq ft | 2,121 sq ft |
| 2,000 sq ft | 2,108 sq ft | 2,236 sq ft | 2,404 sq ft | 2,828 sq ft |
| 2,500 sq ft | 2,635 sq ft | 2,795 sq ft | 3,005 sq ft | 3,536 sq ft |
| 3,000 sq ft | 3,162 sq ft | 3,354 sq ft | 3,606 sq ft | 4,243 sq ft |
Quotes are usually given per square foot of roof surface, so the pitch matters — the same house at 12/12 has about a quarter more roof to clean than at 4/12.
Zinc or copper strips near the ridge suppress regrowth for years — rain carries a trace of metal down the roof. Cutting back overhanging branches removes the shade and damp the algae needs. Between them they make the next clean much further away, and both are cheap next to repeating the job.
Per square foot of roof surface, not of the footprint — so pitch matters. The same house at 12/12 has about a quarter more roof to clean than at 4/12.
Never, on asphalt shingles. It strips the granules, voids most warranties and takes years off the roof. The correct method is soft washing — low pressure, a cleaning solution, dwell time, then a gentle rinse.
Pitch and height above all, then how established the growth is, the covering — tile cracks underfoot — and how much landscaping below needs masking and pre-wetting.
Zinc or copper strips near the ridge, so rain carries a trace of metal down the roof, and cutting back overhanging branches. Both are cheap next to repeating the clean.
Doing it yourself? Follow how to clean a roof safely before you climb up with a sprayer.
Choosing the cleaner? The best roof cleaners are compared for moss and algae streaks.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.