Will a house wash strip your paint? Not if the method is right
No — not if the method is right. High pressure strips paint; a soft wash does not. Soft washing works on chemistry and dwell time at roughly garden-hose pressure, so nothing mechanical touches the coating. James Hardie's maintenance bulletin specifies gentle washing for fibre-cement cladding, not high pressure. Sound paint survives it. Paint that was already failing was already gone.
The damage comes from the lance, not the water
Water does not strip paint. Force does. A pressure washer takes ordinary mains water and concentrates it into something closer to a blade — enough to cut a line into softwood if you hold it still. Point that at a painted wall and the coating is simply in the way. A soft wash never goes near that. It runs at close to garden-hose pressure and lets the cleaning solution do the work: apply, let it dwell, rinse. Chemistry lifts the mould and grime; the water only carries it away.
The trouble is that both jobs get advertised as house washing, and the quotes look similar. One turns up with a lance and a ladder and is done in two hours. The other turns up with a solution mixed for each surface, works elevation by elevation, and takes longer. You are not buying pressure, and you should not be paying for speed. Ask which method is going on your walls before anyone starts. That answer is the whole difference between a clean house and a repaint you had not budgeted for.
What high pressure actually does to a house
High pressure does four visible things to a wall, none of them good. It gets under paint that has already lost its grip at an edge or a blister and peels the strip back further. It etches render, leaving pale wand marks that appear the moment the surface dries. It furs timber, raising the grain so the next coat sits on fuzz. And on weathered fibre cement it can cut into the face of the sheet — which is the finish the cladding was relying on to keep looking like cladding.
The fifth thing is the one you cannot see. Weatherboards, cladding sheets and window flashings are built to shed water falling down. They are not built to resist water arriving sideways under pressure. A lance held beneath a lap joint or run across a window seal pushes moisture into the wall cavity, where it has no easy way out. Nothing looks wrong on the day. It shows up later as swollen board ends, paint blistering from behind, or a stain inside a wall that nobody connects to a wash six months earlier.
The maker of your wall already wrote the method down
You do not have to take a cleaning company's word for any of this. James Hardie's maintenance bulletin for its fibre-cement products specifies gentle washing — low-pressure water and a soft brush — not high pressure. That is the company that made the cladding on a large share of Sydney's newer homes and renovations, putting in writing how it wants that cladding cleaned. It is the closest thing this trade has to a rulebook, and it costs nothing to read before you hire anyone.
Paint systems follow the same logic. An exterior coating is engineered to shed rain, take sun and be cleaned with mild detergent and a soft wash-down. Nothing in that specification includes a concentrated jet. Which is why blast damage is a bad thing to argue about after the fact: strip a coating with a lance and the failure belongs to the method, not the paint, and no manufacturer's warranty is going to absorb it. Match the method to what the surface was built for and the damage question never comes up.
A soft wash reveals failing paint. It does not cause it
Here is the part most cleaners would rather not say out loud. A soft wash can absolutely leave a bare patch — and when it does, the paint in that patch had already let go. Coatings fail from the substrate up. They chalk in the sun, lose adhesion, and blister quietly under a film of mould. What was holding the flake in place was the dirt. Take the dirt away gently and the flake leaves with it. The wash did not create that failure. It found it.
The same candour cuts the other way. Washing will not put back colour the sun has taken out — a faded wall comes back clean and still faded, just evenly so. It will not re-bond a coating that has lost its grip, hide chalking, or close hairline cracks in render. If your walls come up properly clean and still look tired, the answer is not more washing. It is paint. Better to learn that from a wash than from a fresh repaint that lifts in its second summer.
Washing before a repaint is the feature, not the risk
Painters price on the assumption that the substrate handed to them is clean, dry and sound. A soft wash delivers all three, and doubles as a survey: failed sealant, flaking patches and cracked render all become visible once the grime is off. Book it roughly a week before the first coat so the walls dry right through, then let the painter quote what is actually there rather than what the dirt was hiding. Prep done properly is the cheapest part of any repaint, and the part every guarantee quietly depends on.
Cost is the easy bit. House soft washing starts at $300, and most single-storey Sydney homes land between $420 and $960 depending on wall area; two storeys adds around 40%, and putting gutters or windows on the same visit saves 5-15%. The Schmick instant quote asks a few questions about the house and returns a firm, bookable price in about 60 seconds — it holds unless the place turns out to be materially different from what you described. Get the number, book the right method, and keep your paint on the wall.