Roof cleaning cost calculator
Roof cleaning is priced on roof area, which is bigger than the footprint because of pitch, and it is the one job on this site where the method is not negotiable. The asphalt shingle manufacturers’ own association rules out pressure washing outright. What is being sold is a low-pressure hypochlorite application, a dwell, and a gentle rinse.
Asphalt shingle roof estimate
Estimated price range
$880 - $1,650
Soft wash only — never pressure PSI · Low-pressure soft-wash tip · 77-121 min on site
Detergent: ~3% SH, 15-20 min dwell (ARMA). This is a planning band, not a survey figure: measure the site and price your own labour.
PSI & nozzle quick reference
- 0 degRed
- Spot jet. Etches most surfaces.4000 PSI
- 15 degYellow
- Stripping bare concrete.4000 PSI
- 25 degGreen
- General concrete and walkways.3500 PSI
- 40 degWhite
- Siding, wood, vehicles.1500 PSI
- ~65 degBlack
- Detergent draw, low pressure.500 PSI
Footprint to roof area
Multiply the ground footprint by a pitch factor. A 1,500 sq ft footprint on a 6/12 roof is about 1,680 sq ft of shingle; the same footprint on a 10/12 is nearer 1,950 and moves the job into the hard access band, because that pitch is not walkable.
| Pitch | Multiplier | Working from |
|---|---|---|
| 4/12 — shallow | 1.06 | Walkable with care |
| 6/12 — common | 1.12 | Ladder and reach; do not walk it wet |
| 8/12 | 1.20 | Ladder only |
| 10/12 and steeper | 1.30 | Ladder and extension wand, hard band |
Pitch multipliers are geometry: the roof plane is the hypotenuse of the run and the rise. Nothing sourced, nothing assumed.
The ARMA method, in order
- Wet everything below. Beds, lawn, downspout outlets. Then wet them again mid-job.
- Apply from the ladder, working the gun across the plane. Do not walk a wet roof.
- Dwell 15–20 minutes. The algae dies in that window; scrubbing does nothing but shed granules.
- Rinse gently, top down, at garden-hose pressure. Then rinse the landscaping a third time.
Surface damage risk
Warranty and access
Worked example
A 1,500 sq ft footprint on a 6/12 pitch is about 1,680 sq ft of shingle. Heavy algae streaking on the north plane, ladder work throughout. At $0.40–$0.75 times 1.25 for condition and 1.15 for awkward access, the band lands near $965–$1,810 — and the dwell means the crew is on site far longer than the machine is running.