Exterior house washing: how to do it, and how often

"Pressure washing your house" is one of those phrases that quietly causes a lot of damage, because for almost every house exterior the correct answer is not high pressure. A proper house wash is a low-pressure, chemistry-led clean that strips mould, algae, cobwebs, dust and pollution film off your walls without pushing water where it shouldn't go. Here's how it works and how often your place needs it.

What exterior house washing actually removes

• Mould and algae — the green and black film that forms on shaded walls, especially the south side and anywhere near a fence line or garden bed.
• Lichen — the crusty grey-green patches that grip render and mortar and won't hose off.
• Dust and pollution film — the invisible grey layer that dulls paint colour. Most people only notice it once a section has been cleaned.
• Cobwebs, wasp mud and insect residue — concentrated under eaves, around windows and in corners.
• Rust and bore-water staining — streaks running down from gutters, brackets and sprinkler overspray.

Soft washing, not blasting

Soft washing uses pressure barely above a garden hose, combined with a solution that kills mould and algae at the root. The chemistry does the work; the water just rinses. Because the growth is killed rather than knocked off, the finish stays clean roughly twice as long as a high-pressure blast that leaves spores behind. We cover the full comparison in soft washing vs pressure washing.

Surface	Method	Watch out for
Rendered walls	Soft wash	Pressure cuts permanent wand marks into the top coat
Painted brick	Soft wash	Pressure flakes paint at the edges and hairline cracks
Face brick	Soft wash, low pressure rinse	Blowing out old, soft mortar joints
Weatherboard & fibro	Soft wash, always downward	Water driven up under the boards into the wall cavity
Colorbond cladding	Soft wash, soft brush	Abrasives and harsh solvents dulling the finish
Eaves, soffits, fascia	Soft wash	Water forced into vents and roof space
Windows & seals	Low pressure rinse	Breaching seals and flooding the inside sill

The method, step by step

1. Prep the perimeter. Close windows, move furniture and pots clear, cover or pre-wet plants against the wall, and isolate outdoor power points.
2. Knock down cobwebs and loose debris. A dry pass with a soft brush on a pole saves smearing everything into a paste later.
3. Apply the cleaning solution bottom-up. Working upward stops concentrated solution running down dry wall and leaving streaks that are hard to remove.
4. Let it dwell. Ten to fifteen minutes. Re-mist if it starts drying, particularly on a warm day.
5. Agitate the stubborn spots. Lichen and heavy mould in sheltered corners need a soft brush, not more pressure.
6. Rinse top-down at low pressure. Always angle downward on weatherboard and cladding so water runs the way the boards shed it, never up underneath.
7. Finish the details. Rinse windows and frames, then hose down the paths and driveway below so you're not leaving a dirty tide line. If you're having the glass properly cleaned, that goes last, after all the wet work.

How often should you wash your house?

Situation	Suggested frequency
Standard suburban home, open aspect	Every 18–24 months
Shaded or south-facing walls	Every 12 months
Close to trees, a damp fence or a creek line	Every 12 months
Before selling or listing photos	One to two weeks before the shoot
Before repainting	Always — paint won't bond over mould or chalking

The economics favour doing it regularly. An annual or biennial wash is a straightforward job; a wall that's been left for eight years needs pre-treatment, a second pass and sometimes hand agitation, and it costs accordingly.

Where DIY house washing goes wrong

• Water intrusion. Aiming upward under weatherboards, eaves or cladding laps pushes water into the wall cavity, where it does slow, invisible damage.
• Wand marks on render. Instant and permanent. Rendered walls are the single most commonly wrecked surface in DIY washing.
• Streaking. Applying solution top-down, or letting it dry on the wall, leaves runs that can be harder to remove than the original grime.
• Plant damage. Undiluted solution straight onto garden beds kills plants. Pre-wetting and rinsing afterwards prevents it.
• Ladders. Most serious injuries in this work come from working at height off an unstable ladder with a hose in one hand, not from the machine.

What it costs

A house exterior soft-wash in Canberra usually falls between $250 and $600, from around $249. Storeys, footprint, condition and access set the number. Because the bulk of the cost is mobilising the gear, adding the roof, gutters or the driveway to the same visit is far cheaper than separate bookings. Full ranges are in the Canberra cost guide, and if the mould is the main problem, see removing mould from a house exterior.

FAQs

How often should you pressure wash your house?

Every 12 to 24 months for most Canberra homes. Walls that face south or sit in permanent shade, or anything close to trees or a damp fence line, usually need doing annually because mould re-establishes faster there. If you can see green or black film forming, it's already overdue.

Can I pressure wash my house myself?

You can wash a single-storey house yourself if you use low pressure and a cleaning solution rather than blasting it. The real risks are forcing water up under weatherboards and eaves, stripping paint, carving wand marks into render, and working off a ladder. Anything two-storey is best left to someone with the reach gear and insurance.

How much does house washing cost in Canberra?

A house exterior soft-wash typically runs $250 to $600, starting from around $249. Double-storey homes generally sit 30–50% higher than the single-storey equivalent because of the extra time, reach equipment and safety setup involved.

What's the best time of year to wash a house in Canberra?

Spring and autumn are ideal — mild temperatures let cleaning solutions dwell without flash-drying, and surfaces dry properly afterwards. Avoid washing during a frost, in freezing conditions, or in the middle of a hot afternoon when solution evaporates before it can work.

Does house washing damage paint?

A correctly done soft wash won't. High pressure will — it lifts and flakes paint, especially on older weatherboard, and drives water into joints. That's exactly why house exteriors are soft washed at low pressure with cleaning chemistry rather than blasted.

How long does a house wash take?

Most single-storey homes take two to four hours. A large or double-storey house, or one with heavy mould that needs pre-treatment and a second pass, can be most of a day.