How often to wash down a coastal house to make the paint last

Wash the exterior once a year at an absolute minimum, and twice a year if you are within a few hundred metres of open sea or the harbour edge. That one habit does more for the life of an exterior paint job than anything else you can do after the painters pack up.

Salt does not come off on its own. Rain deals with the surfaces it actually strikes and leaves everything else coated. Resene's maintenance guidance puts annual washing on every painted house as the baseline, and on a salt-blown site that is the floor rather than the target.

What is salt actually doing to the paint?

Airborne salt holds moisture, so a salted surface spends far more hours damp than the forecast suggests, and where there is steel underneath it starts corrosion that lifts the coating from behind. Resene's maintenance guidance singles out salt blown areas that rain does not wash, along with galvanised steel under canopies, as needing particular attention, which is exactly why a coastal washdown has to be a schedule rather than a one-off.

How often, by exposure?

Where the house sits	Suggested washdown	Reason
Open south coast, front row to the sea	Twice a year	Constant salt load, and wind drives it into every sheltered pocket
Harbour edge and exposed eastern bays	Twice a year	Salt spray plus southerly rain that only hits one or two elevations
Coastal but set back a few streets	Once a year	Lighter salt load, still enough to build up under eaves
Inland hill and valley suburbs	Once a year	Mostly about grime, pollen and mould rather than salt
Any sheltered area, anywhere near the coast	Every wash, plus a plain water rinse in between wherever you can reach it	These never self-clean, so hand washing is the only thing that takes salt off them

Timing matters as much as frequency. If you only do it once, do it at the end of winter, once the worst of the southerlies have finished. You are removing a season of accumulated salt and mould before the surface dries out and bakes it on over summer. If you are doing it twice, put the second pass at the end of summer so the film goes into the wet months clean.

Treat those intervals as a starting point and let the house correct them. A few months after a wash, run a finger along a soffit or the sheltered wall under a carport. If it already comes away with a gritty film, that pocket needs doing more often than the rest of the building, and a hose and five minutes every few months is far cheaper than repainting one elevation early.

Which parts actually need the attention?

• Soffits and the undersides of eaves, all the way into the corners
• The sheltered face of any wall under a deck, carport or canopy
• Window heads, sills and the top edges of joinery where salt collects in the rebate
• Metal spouting, downpipes, brackets, and every exposed screw head
• Handrails, balustrades and anything you touch, because hand oils hold salt
• The back of the garage door and the inside face of gates

The main wall faces below the eaves matter least. Rain already does most of that work for you.

Why the rinse matters more than the scrub

The job of a coastal wash is to carry salt off the building rather than move it around, which makes the rinse the part that actually counts. Use more fresh water than feels necessary, keep going after the surface looks clean, and pay attention to the corners and rebates where runoff pools instead of draining, because those are where a concentrated salt line gets left behind.

Water blasters are where the damage happens. High pressure at close range drives water behind boards and into joinery joints, strips coating that was still sound, and forces water into places that then take weeks to dry out in a Wellington winter. Stand back, keep the pressure low, and treat a blaster as a rinsing tool rather than a stripping tool.

Think about where the water goes, too. It runs down the drive, into the gutter and into the stormwater system, which discharges to the sea rather than to treatment. If your house was built in the 1980s or earlier and you are dislodging flaking paint, that flaking paint may contain lead and is worth testing for it, and it needs to be caught on sheeting rather than hosed into a drain.

Is this genuinely a DIY job?

On a single storey house with flat ground around it, yes, and you should just do it. A broom, a hose and two hours twice a year is the best value maintenance available on a painted house.

On a steep section it stops being sensible. A lot of Wellington houses sit above a bank with no safe footing on the downhill side, and a ladder on a slope with a wet broom in one hand is how people end up in hospital. If the only way to reach a wall is a ladder on uneven ground, get someone in, or leave that elevation to the next scheduled maintenance visit when access is set up properly. Scaffolding on a difficult site runs $1,500 to $4,000 or more at 2026 prices, so it is not something you put up to do a wash, but it is worth pairing a full clean with any work that needs access anyway.

Does washing actually buy you years?

It buys you the top of the range instead of the bottom of it. Resene's published expectations for exterior systems are 7 to 10 years for a quality three-coat acrylic on timber weatherboards, 5 to 7 years for an acrylic system on metal, and 5 to 7 years on window sills and other slanted surfaces. Those are ranges, and where a particular house lands inside its range comes down to exposure and maintenance. A washed house lands high, an unwashed coastal house lands low.

Put money against it. An exterior repaint in 2026 sits somewhere between $6,000 and $20,000 or more depending on size, condition and access. Adding two or three years to that cycle, for the cost of a bottle of house wash and an afternoon, is the cheapest return available on a painted house. It is also worth walking the roof line while you are at it, because a low pitch roof holds salt and grime for exactly the same reason a soffit does.

When is washing not the answer?

When the coating has already gone. If the surface is heavily chalking so a hand comes away coloured, if paint is lifting in sheets, if there is rust breaking through from underneath, or if there is soft timber behind the film, washing is not maintenance any more. It is the first step of a preparation job, and the rest of that job needs to follow within the same season rather than being left another year.

The other case is where salt is already trapped under a lifted film. Washing over the top of that seals the problem in. It has to be stripped back, washed, and recoated properly, and doing it in the wrong order is how a repaint fails inside two winters.

If you want an honest read on whether your place needs a wash or a repaint, we will come and look and tell you which. Get in touch.