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House washing cost calculator

House washing is priced on wall area, not floor area, and it is a chemistry job. The pressure that cleans a driveway will drive water behind vinyl and into the sheathing. What you are selling is a dilute hypochlorite mix, a surfactant that makes it cling, a dwell, and a low-pressure rinse — plus the time spent protecting the planting.

Vinyl or fibre-cement siding estimate

Estimated price range

$360 - $810

100-500 (soft wash) PSI · Black soap then 40 deg white rinse · 45-72 min on site

Detergent: 0.5-1.5% SH + surfactant. This is a planning band, not a survey figure: measure the site and price your own labour.

Photograph-style house corner in vinyl siding, algae-green on one side of the diagonal and bare clean on the other
Soft wash
Grey vinyl siding at a house corner, algae on one side of the cut and bare cladding on the other.

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

Estimating wall area without a ladder

Perimeter times wall height is close enough to quote from. A 40 x 30 ft single-storey house has a 140 ft perimeter; at 10 ft to the eave that is 1,400 sq ft of wall before gables. Add roughly 100–150 sq ft per gable end. Two storeys doubles the height, not the perimeter — and pushes the job into the hard access band because the top course needs reach.

HousePerimeterWall sq ftAccess band
Single storey, 1,200 sq ft floor1401,400Easy
Single storey with two gables1401,650Easy
Two storey, 1,800 sq ft floor1603,200Hard
Split level with a walkout1502,400Awkward

The mix is the job

Siding wants roughly 0.5–1.5% sodium hypochlorite at the wall, plus a surfactant so it clings long enough to work. From 12.5% stock that is about one part stock to eight or twelve parts water, or a downstream injector drawing at 1:10 with stock in the bucket. Anything stronger is a roof mix and will take the sheen off painted trim and burn foliage.

Surface damage risk

High pressure on lap siding forces water up behind the courses and into the wall assembly. The damage shows up months later as staining, swollen sheathing or mould inside — long after the invoice cleared. Soft wash means low pressure by definition, not just a wider tip.

Painted and cedar siding

Chalking paint transfers to a mitt with a wipe. Test before you quote: a chalked wall may need to be told it is a paint job, not a wash job. Cedar takes a percarbonate cleaner, not hypochlorite, or it darkens.

Worked example

1,650 sq ft of vinyl on a single-storey with two gables, moderate green on the north elevation, spigot on site. At $0.20–$0.45 with no multipliers that is roughly $330–$740; the time line reads 41–66 minutes of application and rinse, and realistically half a day once bed protection and the walk-round are counted.

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