I've lost count of the peeling exteriors where the last painter skipped the wash, or blasted the house with a hire-shop machine and painted it the next morning. Both fail the same way. Here's how we wash a house before painting, what pressure suits what surface, and how long it needs to dry.
Why paint fails over an unwashed wall
Paint fails at the bond line, where the new coat meets whatever was on the wall when it went on. If that layer is salt, chalk, mould or dust, the paint is stuck to the contaminant, not the house, and comes off with it.
Salt is the worst because it's hygroscopic: it pulls moisture out of the air. Salt under paint keeps drawing water through the coating, and within a couple of summers the ocean-facing wall is blistering while the back of the house looks fine.
Chalk is the powder old acrylic turns into as UV breaks it down. Run a hand across a north-facing wall and if it comes away white, that's chalk. Mould and algae are alive and keep growing under a new coat. Dust and cobwebs still cut adhesion. A proper wash deals with all four in a morning.
What we're actually washing off
Front row: Coogee, Bondi, Bronte and Maroubra beachfront
Within a couple of hundred metres of the surf, salt is the main job: a dull grey bloom on the seaward wall, sometimes crystals on the sills. A good repaint on those walls lasts 5–7 years, and skipping the wash is the fastest way to make that three. Our guide to how long exterior paint lasts near the beach covers the exposure bands.
A few streets back
Most of Coogee, Bondi and Bronte sits here. Still salt, just less of it, plus the usual chalk and mould. These homes run a 7–10 year cycle.
Inland: Randwick, Kensington, Kingsford
Salt barely registers a couple of kilometres in. The wash is mostly about chalk on the north and west walls, mould on the south side and behind hedges, and plain dirt. Less critical, and I still won't paint without it. Done properly, these houses go 10–12 years or more between repaints.
On every house the wash also lifts the loose, flaking edges that were coming off anyway, which shows us where the scraping has to happen.
Pressure wash or soft wash? It depends on the surface
The pressure washer is a tool, not a method; what comes out of the nozzle has to suit the wall. "Soft wash" means low pressure, garden-hose-plus, with the cleaning done by the solution and a brush rather than the water. As a guide:
| Surface | What we use | Why |
|---|---|---|
| Sound cement render | 1,500–2,500 psi, 25–40° fan tip, held 300 mm off the wall | Takes the pressure; shifts chalk and salt |
| Face brick | 1,500–2,000 psi, fan tip; lower on old lime mortar | The mortar is what blows out |
| Weatherboard and timber trim | Soft wash under 1,000 psi, wide tip, washed downwards | High pressure drives water behind the boards |
| Old or soft render (hollow when tapped) | Soft wash, brush and rinse only | Pre-war render holes under a jet |
| Fibro or any pre-1990 sheeting | Never high pressure. Wet, low-pressure hand wash only | Assume asbestos; nothing that could release fibres |
| Colorbond and metal cladding | Low pressure, fan tip, washed with the laps not into them | Water forced into the laps sits against bare steel |
| Decks | Low pressure, along the grain, with a deck cleaner | Anything more furs the boards |
Weatherboard homes are the ones most often wrecked by a wash; our weatherboard painting guide covers the whole job.
The damage high pressure does
A 3,000 psi jet finds every gap between weatherboards and drives water into the wall cavity, where it sits for weeks. Paint the outside, seal it in, and the boards cup and the paint bubbles from behind.
On timber, high pressure lifts the grain into a fuzzy surface that paints rough and fails early; decks are worse again, which is why our deck restoration guide spends so long on washing gently.
Old lime mortar and soft pre-war render blow out under a turbo nozzle, adding a patching job before painting can start. Aim a jet at perished window putty or rubber seals and the water ends up inside the frame.
And a jet strong enough to strip paint strips the good with the bad, leaving a hard edge that shows through every coat. Sound paint gets left alone. Failing paint gets scraped and feathered by hand, not blasted.
Mould needs treatment, not just water
Water alone spreads mould. Blast a mouldy south wall and you've spread live spores across the whole elevation; it's back within a year, under your new paint.
So mould gets treated first: a diluted sodium hypochlorite solution (pool chlorine) or an oxygen-bleach product, left to dwell for 10–20 minutes. The dwell time does the killing. Then the wash removes what's dead and the wall is rinsed properly. Plants get soaked with clean water before and after, and covered where the run-off is heaviest.
How long after pressure washing can you paint?
As a guide, 2–3 dry days. Not 2–3 days: dry days. A shower on day two resets the clock. Weatherboards look dry within hours, but the end grain and laps hold water for days, so I want a moisture meter reading under 15% before primer goes near them.
Render and brick soak water up like a sponge. A sunny north wall in summer can be ready in 48 hours. A south wall in July, with no direct sun and dew every morning, can take a week. That's why winter exteriors get sequenced around the house, sunny walls first.
Paint over damp and you've sealed water in. The sun heats the wall, the water turns to vapour and pushes the film off in blisters. That's the first-summer failure, and it's avoidable by waiting.
What to expect on the day
A full house wash takes half a day to a day. The machine is a commercial petrol unit, about as loud as a mower. We check every window and door is closed, cover power points, light fittings and intercoms, and hose down and cover plants near the walls. Run-off is mostly water and dead grime, and it goes where rain goes.
What a wash does not replace
A clean wall is the start of the prep, not the prep. Once it's dry we still scrape the loose paint, feather and sand the edges, fill, spot-prime bare timber and chalky areas with a bonding primer, and re-caulk the joints. The wash makes that possible; it doesn't do it for you.
Our surface preparation page walks through the full sequence, and it's why we can put a 5-year written guarantee on exterior work. The right product matters too; see our guide to the best paint for coastal homes.
What it costs
If we're painting the house, the wash isn't a line item you can cut; it's built into every Proview exterior quote because the guarantee rests on it. A full exterior repaint in the Eastern Suburbs runs $8,000–$25,000+ depending on size, access and condition; our house painting cost guide breaks that down.
As a standalone house wash without painting, a typical Eastern Suburbs home is $400–$1,200 as a guide. Size, height, mould treatment and whether driveways and paths are included move it within that range. For beachfront homes a wash every year or two between repaints is the cheapest maintenance there is; details are on our pressure washing service page, or get in touch and we'll quote it.
Frequently asked questions
Do you need to pressure wash before painting?
Yes, or at least wash it. Every exterior repaint needs the salt, chalk, mould and dust removed before the first coat, or the paint bonds to the contaminant instead of the wall. Whether that is a pressure wash or a low-pressure soft wash depends on the surface.
How long after pressure washing can you paint?
As a guide, 2–3 dry days in summer and up to a week on a shaded south wall in winter. Timber should read under 15% on a moisture meter before primer goes on. A shower in between resets the clock, and painting over damp is the usual cause of blistering in the first summer.
Can you pressure wash a weatherboard house before painting?
Only at low pressure. High pressure drives water behind the boards, furs the timber and strips sound paint. Weatherboards get a soft wash: mould treatment, a wide fan tip at garden-hose-plus pressure washed downwards along the boards, then several dry days before scraping or priming.
What is the difference between soft washing and pressure washing before painting?
Pressure washing uses the force of the water, typically 1,500–2,500 psi through a fan tip, and suits sound render, brick and concrete. Soft washing uses low pressure and lets a cleaning solution and a brush do the work. Timber, old render, fibro and Colorbond get soft washed because they cannot take the pressure.
How much does it cost to pressure wash a house before painting?
If we are painting the house, nothing extra: the wash is built into every Proview exterior quote. As a standalone house wash, a typical Eastern Suburbs home runs $400–$1,200 as a guide, depending on size, height, mould treatment and whether driveways and paths are included.