There is a particular kind of phone call that comes in around this time of year. The house was painted eighteen months ago, it looked sharp for a season, and now the south wall is patchy and the paint is peeling off in sheets you can pull away with your fingers.
Nine times out of ten the paint was fine. The surface underneath it was not.
Salt does not rinse off in the rain
If you live anywhere between Helensburgh and Batemans Bay you have a film of salt on your walls. You cannot see it. It builds up quietly on the weather side of the house, and rain does not remove it, because rain arrives horizontally with more salt in it.
Paint bonds to the surface it touches. If that surface is a layer of salt sitting on top of the render, the paint bonds to the salt. When the salt eventually moves, the paint goes with it, which is why exterior failures usually start on the side facing the water and work around.
A wash before painting is not cosmetic. It is the difference between paint stuck to your house and paint stuck to something that is on its way off.
Mould grows back through paint
Mould and lichen are the other one. Painting over mould does not kill it. It sits there under the film, keeps feeding on whatever it was feeding on, and pushes back through as dark shadowing within a year or two. On the shaded southern side of a house, under eaves and behind shrubs, this happens fast.
Killing it means a chemical wash, left to dwell, then rinsed. Not a quick blast with a wand. The blast removes what you can see and leaves the spores in the surface texture, which is the worst outcome, because now the wall looks clean and nobody thinks to treat it.
Pressure is the least interesting part of pressure washing
This is where most weekend jobs go wrong. Somebody hires a machine, turns it up as far as it goes, and carves lines into the render or drives water in behind the weatherboards.
Timber, older render and anything already chalking want low pressure and the right chemistry. Concrete driveways and pavers will take a lot more. Matching pressure to the surface is most of the skill, and it is the part a hire shop cannot sell you. We go through this on the exterior cleaning page, but the short version is that if the machine is doing the work rather than the detergent, something is about to get damaged.
Water forced up under a weatherboard lap or behind a window flashing does not evaporate. It sits in the wall cavity for weeks. Painting over that traps it.
Where the water goes afterwards
Washwater carrying detergent, mould treatment and paint chalk is not clean water, and it should not go down a stormwater grate. Stormwater in NSW runs untreated into the nearest creek and out to the ocean, and it is an offence to pollute it. The NSW EPA is the authority on that.
In practice it means keeping runoff on the garden or the lawn where the soil can deal with it, blocking the grate if the fall is wrong, and being sensible about what you are washing off. Old flaking paint on a pre-1970 house is a separate question again, because lead is likely, and that changes how the debris has to be contained.
Then wait
Rendered and masonry walls hold water for longer than people expect after a wash. Timber longer still, especially in winter when nothing dries. Painting a wall that reads dry to the hand and is not dry inside gives you blistering later, sometimes months later, and no amount of good paint prevents it.
There is no universal number of days. It depends on the substrate, the weather that week and which way the wall faces. On a west-facing brick wall in February it might be next morning. On a south-facing weatherboard in July it might be most of a week. The point is to check rather than assume, and to build the wait into the plan instead of discovering it on the day the painting is meant to start.
What stays off our list
Washing and painting are general trade work. A few things that often come up alongside them are not.
If clearing the gutters shows up rusted-through guttering or damaged downpipes, that is roof plumbing, a separate trade in NSW that we do not work in, and it goes to a roof plumber. Anything electrical is a different case again: the light fittings and sensors people ask us to move while the ladders are up always need a licensed electrician, whatever the job costs. We will tell you what we are looking at and point you at the right trade rather than have a go at it. The licensing rules behind that are worth a read if you have not come across the $5,000 threshold before.
Everything else — the wash, the prep, the paint, the bits of timber that need filling first — is the actual job, and the order it happens in decides how long it lasts. If you want us to look at a house before you book a painter, get in touch.
Want a hand with this at your place? Get a free quote or call 0450 959 936.