Washing before painting: the prep coat nobody prices in
Yes — wash the house before the painter arrives. Paint bonds to whatever sits on the wall, and after a few Sydney years that is chalk, salt film and mould — a substrate no coat will hold to. Painters quote assuming a clean wall. A soft wash runs from $300, most single-storey homes $420-$960, done about a week before the first coat.
Paint sticks to whatever is underneath it
Paint does not bond to your wall. It bonds to whatever is on the surface of your wall — and after a few Sydney years, that surface is rarely paint. It is chalk from the old coating breaking down in the sun, a film of salt if you are anywhere near the water, and mould in every shaded corner. Roll a new coat over that layer and the paint sticks to the chalk. The chalk sticks to nothing.
The failure is slow and then sudden. The new coat looks fine at handover, fine for a season, then starts flaking wherever the substrate never held it — usually the southern wall first, where mould lived under the film. Worse, mould painted over is not mould killed. It keeps growing under the coat and ghosts back through as grey shadowing you cannot wipe off. At that point the fix is not a wash. It is another repaint.
Your painter is assuming a clean wall
Read a painting quote closely and you will find prep means sanding, filling, spot-priming and masking. It rarely means washing whole elevations, and it almost never means treating mould properly. That is not the painter cutting corners — surface cleaning is a different trade with different gear, and pricing it into every job would make every quote uncompetitive. So the assumption sits there quietly: the substrate you hand over is sound and clean.
The assumption has teeth. Paint guarantees and workmanship warranties are tied to correct surface preparation, and a coat applied over chalk, grime or active mould gives everyone an exit if it fails. If the wall was dirty when the first coat went on, the failure becomes your problem, not theirs. Washing first is not gold-plating the job. It is the difference between a warranty that holds and one that was void on day one.
Soft wash is the right prep — pressure is not
The instinct is to hire a pressure washer and blast the place the weekend before. Do not. High pressure drives water behind cladding and into window seals — exactly the moisture a painter needs gone — and it scars soft surfaces: it furs timber, etches render, and can cut into weathered fibre cement. James Hardie's own maintenance bulletin specifies gentle washing for its fibre-cement cladding, not high pressure. The manufacturer of the wall is telling you how to wash the wall.
A soft wash works the other way around. Low pressure, the right detergents and dwell time do the lifting: the chalk rinses off, the salt film dissolves, and the mould is killed at the root rather than beheaded — which is what stops it ghosting back through the new coat. What is left is a dull, clean, sound surface. That is exactly the wall a primer wants, and it is a surface no amount of pressure can produce.
Timing: wash a week out, not the day before
Book the wash for roughly a week before the painter starts. That gives the walls time to dry right through — paint over a damp substrate and you have swapped one adhesion problem for another — and gives you a window to see what the grime was hiding. A soft wash routinely uncovers hairline render cracks, failed sealant and flaking patches that were invisible under the dirt. Better your painter finds those in the quote than in the second week.
It is also the cheapest moment to deal with everything else at height. With the poles and ladders already on site, adding gutters to the same visit costs less than booking them separately — bundling services on one visit saves 5-15% at Schmick. Windows are the exception: painters leave a fine dust of their own, so many owners run those after the final coat instead. Either order works. Doing neither does not.
What the prep coat actually costs
House soft washing starts at $300, and most single-storey Sydney washes land between $420 and $960 depending on wall area. Two storeys adds about 40%. Against a full exterior repaint — routinely a five-figure job on the North Shore or in the Eastern Suburbs — the wash is a rounding error, and it is the layer everything above it depends on. Skipping it to save a few hundred dollars is a strange way to protect ten thousand.
You do not need a site visit to find your number. The Schmick instant quote asks about the house and returns a firm, bookable price in about 60 seconds — a real figure that holds unless the place is materially different from what you described. Run it before you sign the painting quote, put the wash a week ahead of the first coat, and hand your painter the one thing every guarantee assumes: a clean wall.