TL;DR
Yes, pressure washing will remove paint that is not firmly bonded, and it will lift sound paint too if the pressure is high or the tip is narrow. Painted wood siding should be soft washed with a detergent at low pressure, kept under roughly 500 to 800 PSI if a machine is used at all, and tested in a hidden spot before anything else happens.
The short answer
Painted wood can be cleaned safely, but not with the tool most people reach for.
Two things fail at once under pressure. The coating lifts wherever adhesion is already weak, peeling in sheets from a spot that looked perfectly fine. And the wood underneath erodes, because the soft growth between grain lines is much less dense than the hard rings.
Both failures are permanent. A stripe of peeled paint means repainting that elevation, and furred wood will not take a new coating evenly until it is sanded.
The safe version is a soft wash: detergent, dwell time, a soft brush, and a gentle rinse.
Test the coating before you touch it
Old paint tells you what it can take, if you check.
The tape test. Press a strip of masking tape firmly onto a painted area, then pull it off quickly. If paint flakes come away with the tape, the coating is not bonded and washing will make it worse.
The chalk test. Rub a dark cloth across the paint. Heavy powder on the cloth means the coating has broken down at the surface -- chalking -- and it will not survive aggressive cleaning.
The scrape test. Run a fingernail or a plastic scraper along an edge. If paint lifts, that area is already failing.
Look at the age. Exterior paint commonly lasts five to ten years depending on exposure. Coatings well past that, or with visible cracking and blistering, are candidates for repainting rather than washing.
Source: paint manufacturer surface preparation guidance
If any test fails, the honest conclusion is that the wall needs paint work, not a wash. Cleaning it hard will just decide the timing for you.
Homes built before 1978 need a different plan
Paint applied before 1978 may contain lead. Disturbing it -- by pressure washing, scraping, or sanding -- can spread contaminated dust and chips onto the soil and into the house.
If your home dates from before 1978 and you have not confirmed the paint layers are lead-free, do not pressure wash it. Have the paint tested, and use a contractor who follows lead-safe work practices for any disturbance.
This is not a cleaning question. It is a regulated hazard, and washing is one of the activities that disturbs it.
The method for sound painted siding
1. Prep. Close windows, cut power at the breaker to exterior fixtures, cover what you cannot disconnect, and move furniture away from the walls.
2. Soak the plants. Wet beds and shrubs with plain water and keep them wet through the job.
3. Pre-rinse, top down. A gentle hose rinse removes cobwebs and dust and wets the surface so detergent spreads evenly.
4. Apply detergent, bottom up. A mild exterior house wash from a pump sprayer, in sections small enough to return to before they dry.
5. Dwell. Five to ten minutes, out of direct sun, never to dryness.
6. Soft brush. A soft-bristle brush on a pole, worked along the boards, not upward into the laps. No wire brushes and no scouring pads.
7. Rinse, top down. Garden hose, or a pressure washer at low pressure with the widest tip, held well back and angled downward. Keep it under roughly 500 to 800 PSI at the surface. Surface limits across materials are in what PSI each surface can take.
8. Let it dry fully before any inspection, touch-up, or painting.
The full logic of chemistry-over-force is in soft washing and when it applies.
Why angle matters as much as pressure
Wood siding laps like vinyl does. Each board sheds water down the face, and nothing behind it is sealed.
A stream aimed upward or into a lap joint pushes water onto sheathing and framing that dry very slowly. On wood siding that also means water into the back of the boards, which swells them, breaks the paint bond from behind, and causes peeling months later that looks like a paint failure rather than a washing mistake.
Keep every stream angled down, every time. That mechanism is covered in why water behind siding is the real risk.
If you are washing before repainting
Washing before paint is a different job with a different goal. Here you want the loose coating gone, and some contractors will use higher pressure deliberately.
Even then, higher does not mean unlimited. Pressure that furs the wood grain leaves a surface that will not hold paint properly, and the fuzz has to be sanded off before priming -- so aggressive washing can create work rather than save it. That erosion mechanism is the same one described in what high pressure does to a wood deck.
Wood also has to dry completely before painting, which can mean several days after a wet wash. Painting over damp siding traps moisture and causes blistering.
Safety
Never operate a pressure washer from a ladder. The wand recoils and there is no way to brace against it. Anything above safe ground reach gets an extension wand or a contractor.
Never combine a bleach-based house wash with an acidic product such as a rust remover or masonry etcher -- that releases chlorine gas. Never combine it with an ammonia-based glass cleaner either.
Wear eye protection and gloves, and rinse plants before and after.
FAQ
Does pressure washing remove paint?
It removes any paint that is not firmly bonded, and at higher pressures or with a narrow tip it will lift sound paint as well. That is useful when you are stripping before a repaint and destructive when you are only trying to clean, which is why painted siding is soft washed instead.
Can you pressure wash painted wood siding?
Only at low pressure, roughly 500 to 800 PSI at the surface, with the widest tip, held well back and angled downward, and only after testing that the coating is well bonded. In practice a pump sprayer, a soft brush, and a garden hose do the job with less risk.
How do I know if my paint can handle washing?
Press masking tape firmly onto the paint and pull it off -- flakes coming away mean poor adhesion. Rub a dark cloth across the surface; heavy powder means the coating is chalking. If either test fails, or the paint is cracking and blistering, the wall needs repainting rather than cleaning.
What is the safest way to clean wood siding?
A mild exterior detergent applied at low pressure from the bottom up, five to ten minutes of dwell time out of direct sun, a soft-bristle brush along the boards, then a gentle top-down rinse with the stream angled downward. Let it dry fully before any further work.
Can I pressure wash a house built before 1978?
Not without testing the paint first. Coatings from before 1978 may contain lead, and washing disturbs it, spreading contaminated dust and chips into the soil and the house. Have the paint tested and use a contractor who follows lead-safe work practices for any disturbance.
If the wider house needs the same attention, that is what house cleaning services cover.
Painted wood is the surface where a cleaning decision and a repainting decision blur together, and the tests above are what separate them. If you would rather have someone assess the coating before anything gets sprayed, get a quote and we will look at it with you.