Washing a house yourself: a safe DIY guide

Updated 2026-10-06

A single-storey house with light grime is a fair weekend job if you keep your feet on the ground, use a gentle wash and keep the run-off out of the drains. This guide covers what to use, the order to work in, and the signs that it’s time to hand the job to a crew. If you’d rather skip it, our house washing page explains what a professional soft wash includes and costs.

What’s the best thing to wash a house with?

For general dirt, warm water with a mild detergent and a soft, long-handled brush is the safest start. For mould, mildew and lichen you need an exterior house wash product made for the job, usually based on sodium hypochlorite or a quaternary ammonium compound. Follow the label dilution exactly, test a small patch first, and never mix two cleaners together.

The two main product types work differently. Hypochlorite-based washes, related to household bleach, work within minutes and show results on the day. Quaternary ammonium products, sold as spray-and-leave moss and mould treatments, work more slowly and keep going for weeks. Both are hazardous to aquatic life according to their safety data sheets, so both need the run-off controls described further down.

• Read the whole label: dilution, dwell time, surfaces to avoid, and protective gear. Gloves and eye protection are the minimum for any solution stronger than dish soap.
• Protect glass and aluminium: hypochlorite washes can etch them if left to dry, so rinse joinery while the wall is still wet.
• Be careful with homemade bleach mixes: household bleach strengths vary, it can mark paint and plants at full strength, and it is never to be combined with ammonia-based or acidic cleaners.

That last point is a safety issue, not a cleaning tip. Health authorities such as the Washington State Department of Health warn that bleach mixed with ammonia releases chloramine gases, and mixed with acids releases chlorine gas. Both damage the lungs. Use one product, rinse the bucket between products, and work outside with the wind at your back.

Can you pressure wash your own house?

You can, but it’s the riskiest way to wash painted walls, and we don’t recommend it. A home or hire water blaster held close can strip paint, fur up timber, crack plaster and drive water behind weatherboards and window seals. It must never be used on a roof or cladding that could contain asbestos. A garden hose and a soft brush do a safer job.

If you do use a machine on the house, keep it on its lowest setting with the widest fan nozzle, stand well back, and spray downwards, never up under weatherboard laps or into window and door seals. Leave plaster, EIFS and anything with flaking paint alone.

The asbestos rule matters most on roofs. WorkSafe’s asbestos safety alert says high-pressure water is prohibited on asbestos-containing material, which may be present in buildings from before the 2000s and in some decramastic roof tiles. Roofs are not a DIY job in any case, for that reason and because of the fall risk.

How to wash a house step by step from the ground

Pick a dry, mild, overcast morning with no rain forecast. Close the windows, move furniture and cars away, divert the downpipes, and soak garden beds next to the walls. Then work one wall at a time: brush or spray the solution on from the bottom up, let it sit as the label says, and rinse from the top down with the hose.

1. Check the forecast: rain on the way means the job waits. It washes the product off before it works and carries it into the drains.
2. Prepare the site: close windows and doors, cover vents and outdoor power points, bring in washing, and keep children and pets inside.
3. Protect the garden: water plants along the walls first, so any overspray lands on wet leaves and is diluted, and cover vegetable beds.
4. Apply from the bottom up: working upwards stops clean streaks forming as the solution runs down dry wall. Use a pump sprayer or a soft brush on an extension pole.
5. Let it dwell, but not dry: keep within the label’s time and mist the wall if it starts drying in the sun.
6. Rinse from the top down: a garden hose, pointed downwards with the run of the weatherboards, carries everything away.
7. Rinse plants and joinery again: a final hose-down of the beds, glass and aluminium frames takes care of any overspray.

Work on the shady side of the house first and follow the shade around. A wall in full sun dries too quickly for the solution to work evenly, and dried product leaves marks on glass and dark paint.

Keeping wash water out of the stormwater drains

Everything you wash off the house has to stay out of the stormwater drains, because they run untreated to streams and the sea. Auckland Council says even biodegradable detergents aren’t allowed to enter stormwater, and the landowner is responsible for work done on their land. Divert downpipes onto lawn or garden, block or cover nearby drains, and don’t wash when rain is forecast.

The council’s pressure washing and water blasting guidance describes simple controls that work just as well for a DIY wash: disconnecting downpipes and pointing them at unsealed ground, sandbags or sand socks to steer water away from a drain, and a bucket or wet-vac to collect water that pools on paving. Treat moss and mould removers as harmful chemicals and keep them on your section.

This is where a hose-and-brush wash has a real advantage over a water blaster. You use far less water, so there’s much less run-off to manage, and most of it soaks into the lawn before it gets anywhere near a grate.

What to leave to a crew

Leave anything you can’t reach from the ground to a crew: second storeys, high gables, steep sections and every kind of roof. A long-handled brush and a hose will reach most single-storey walls safely. Once a job needs a ladder for more than a quick look, the risk of a fall outweighs the saving, and you should never walk on a roof to clean it.

WorkSafe’s guidance on ladders and stepladders is written for workers, but it applies just as well at home. Ladders are meant for light, short tasks, they offer no protection if you fall, and you should keep three points of contact at all times. Holding a hose or a spray wand on a ladder takes away a hand and pulls you off balance, which is exactly the kind of task that belongs on the ground.

A crew brings a different set-up for height: extension poles and low-pressure pumps that reach a second storey from the ground, and planned fall protection where someone does have to go up. It’s also worth calling one in if the house is large, heavily mouldy or close to the sea, where salt build-up needs a more thorough clean.

Signs the job needs more than a wash

Some things a wash can’t fix, and washing over them can make them worse. Flaking, chalky or bubbling paint, soft or split timber, cracks in plaster, and black stains that come back within weeks all point to a maintenance problem. On older homes, failing paint also raises the question of lead, which changes how any loose paint should be handled.

• Paint coming away: water will lift it further and push moisture into the timber. Scrape and repaint before washing, or wash very gently.
• Lead-era paint: Health New Zealand advises presuming a building from the 1980s or earlier has lead-based paint. Collect every flake and follow their guidance before removing any paint.
• Soft timber or rot: often around sills, the bottoms of boards and under windows. That is a repair job, not a cleaning one.
• Cracked plaster or gaps around joinery: water from washing can get straight in. Get them looked at and sealed before anyone sprays the wall.
• Mould that returns fast: a wall that goes green again within a few weeks may have a moisture problem, such as a leaking spouting or a blocked downpipe, that needs fixing first.

If you spot any of these while you’re washing, stop and deal with that part first. Cleaning is maintenance; it doesn’t replace repairs, and it shouldn’t hide them either.