How often does a house actually need washing?
Every one to two years for most Sydney homes. That is not a cleaner's upsell — James Hardie's maintenance bulletin specifies gentle washing for fibre-cement cladding, and BlueScope's TB-4 requires regular fresh-water washing of Colorbond, more often near marine environments. Salt air, rendered walls and shaded southern faces all shorten the interval. Most single-storey soft washes run $420–$960.
The manufacturers already answered this
You do not have to take a cleaner's word for it. James Hardie — the company behind most of the fibre-cement cladding in Sydney — publishes a maintenance bulletin that specifies gentle washing to keep its boards in condition. BlueScope goes further: its TB-4 technical bulletin requires regular fresh-water washing of coated steel like Colorbond, and states plainly that the interval shortens near marine environments. These are the people who made your walls, telling you in writing that the walls need washing.
Translated to a calendar, that lands at every one to two years for most Sydney homes. Two years if you sit inland with open exposure and regular rain doing part of the job. Closer to one if the house is near salt air, under trees, or rendered. The interval is forgiving — a few months either way changes nothing. Skipping cycles entirely is what changes things, because the grime that builds in year three does not rinse off the way year one's does.
Salt, render and shade set your clock
Salt is the big accelerant. BlueScope's bulletin is explicit that coated steel near marine environments needs washing more often, and the reason is simple: salt settles on the surfaces rain never reaches — under the eaves, on sheltered wall faces, along window heads. In Mosman, Manly or Vaucluse, the haze off the water is quietly loading your walls all year. Rain rinses the exposed faces and leaves the sheltered ones to concentrate.
Render pulls the interval in from a different direction. Its texture holds grime and moisture, and the southern face of a rendered house — the wall that rarely sees direct sun — is where the green tinge starts. Big trees add their own load: sap, pollen, shade, and the organic film that follows all three. A rendered home under gums on the North Shore is an annual wash, whatever the postcode. A brick bungalow in full sun can wait the full two years.
What a wash fixes, and what it cannot
A proper soft wash takes off the salt film, the traffic grime, the cobwebs, the organic growth and the general grey that settles over everything. The colour that comes back is usually a surprise — most owners have forgotten what the house looked like at handover, because the change happened one week at a time over two years.
It will not fix everything, and you should hear that before anyone starts. Chalked and failing paint is a painting job. Cracked render is a rendering job. Rust staining from old fixings does not wash away. A wash reveals those problems honestly rather than hiding them under grime — which is useful, but it is not repair. If a wall needs a trade rather than a clean, we say so and leave it alone.
Gentle is the specification, not a preference
Note what both manufacturers actually ask for. James Hardie's bulletin specifies gentle washing for fibre-cement — not high pressure. BlueScope warns against harsh treatment of its coatings. Neither says blast it. High pressure drives water behind cladding joints and into weep holes, strips paint that was holding on fine, and etches render. It makes a wall look clean in the way sandpaper makes it look clean.
Soft washing is the method that matches the bulletins: low pressure, the right detergents for the surface, and a thorough rinse. It takes longer than pointing a pressure lance at a wall, which is exactly why the cheap operators do not do it. If the quote is suspiciously fast and the machine is suspiciously loud, the house is being treated in the way the manufacturers specifically warn against.
The cost, and the sixty-second answer
House soft washing starts at $300, and most single-storey washes land between $420 and $960 depending on wall area. Two storeys adds about 40% for the access and time. Bundling it with windows or gutters on the same visit saves 5–15%, and if you would rather never think about intervals again, the Schmick Plan puts the wash on a schedule alongside everything else.
So: every one to two years, sooner near salt or shade, gently, by someone who has read the bulletins. The only variable left is your house — its wall area, its storeys, its surfaces. The instant quote takes those and returns a firm, bookable price in about 60 seconds, and it holds unless the place is materially different from what you told us. That is the whole process. No inspection theatre, no callback.