The seven mistakes at a glance
The usual mistakes are using the wrong nozzle tip, holding it too close, fuzzing wood, gouging stucco, forcing water behind siding and windows, working from a ladder and skipping pre-treatment. Nearly all of them come from the same idea: that more pressure means more clean.
In reality, pressure removes loose dirt, while chemistry and dwell time remove stains. Get that balance right and most DIY jobs go well. Get it wrong and you can leave permanent marks in a single afternoon.
Each one is easy to avoid once you know about it.
Mistakes 1 and 2: the wrong tip, too close
Pressure washer tips are color-coded by spray angle. The narrow red zero-degree tip concentrates all the force into a pencil-thin line. It can cut wood, carve concrete and strip paint. For general cleaning, a wide white or green tip is safer, and the black soap tip applies detergent at low pressure.
Distance matters as much as the tip. Moving the nozzle a few inches closer multiplies the force on the surface. Start farther away than you think, test in a hidden spot, keep the wand moving and keep a steady distance. Stopping in one place is how stripes and etched lines appear on concrete.
Also watch the spray when you change direction near edges. Concrete joints, brick borders and the edge of the driveway apron are easy to chip when the wand sweeps across them at close range.
Mistake 3: fuzzing wood
Wood fences, decks and gates are softer than they look. Too much pressure tears up the surface fibers and leaves a fuzzy, splintered texture that holds dirt and takes stain unevenly. Sanding it smooth again is a lot of work.
For wood, use low pressure, a wide tip and a wood-appropriate cleaner. Work with the grain and let the cleaner loosen gray weathering and mildew. Some brown tannin stains respond to an oxalic-based brightener rather than more pressure.
Mistake 4: gouging stucco
Stucco is common on LA homes, from Spanish-style houses to modern builds, and it is easy to damage. High pressure can blast away the texture, chip the finish coat, open hairline cracks and push water into the wall. The marks often show as lighter patches that do not match the rest.
Stucco should be soft washed: low pressure, a cleaning solution applied from the bottom up so it does not streak, time to dwell, then a gentle rinse from the top down. If paint is already peeling, that is a repair and painting job, not a cleaning problem.
Mistake 5: water behind siding and windows
Spraying upward under lap siding, into window frames, around vents or into light fixtures pushes water where it does not belong. It can get trapped in walls, soak insulation or trip electrical fixtures.
Keep the spray angled down or straight on, never up under laps. Give windows, door seals, vents, outlets and fixtures a wide berth and use the lowest pressure that works. Close windows and cover outlets before you start.
Mistake 6: using a pressure washer on a ladder
A pressure washer wand kicks back when you squeeze the trigger. On the ground that is manageable. On a ladder it can push you off balance, and wet rungs make it worse. This is one of the most dangerous ways to do exterior cleaning.
For second-story walls, eaves and gutters, use extension wands from the ground or leave it to a crew with the right equipment. No clean wall is worth a fall.
Mistake 7: skipping pre-treatment
Spraying a stain with plain water and more pressure rarely works. Oil needs a degreaser, mildew and algae need a diluted sodium hypochlorite solution, and rust needs a targeted rust remover. Each needs a few minutes of dwell time, kept damp, before rinsing.
Pre-treatment also protects your surfaces because it lets you clean with less pressure. Keep runoff out of the storm drain, since Los Angeles Municipal Code section 64.70.02 prohibits discharging untreated wash water from paved-surface washing into it. If a job feels bigger than your tools, the instant quote on this page gives you a price to compare.
The order you work in matters too. Clean from the top down so dirty water does not run across areas you already finished, and rinse thoroughly so no cleaning residue is left to dry in the sun.
Key points
The seven mistakes at a glance
The usual mistakes are using the wrong nozzle tip, holding it too close, fuzzing wood, gouging stucco, forcing water behind siding and windows, working from a ladder and skipping pre-treatment. Nearly all of them come from the same idea: that more pressure means more clean.
Mistakes 1 and 2: the wrong tip, too close
Pressure washer tips are color-coded by spray angle. The narrow red zero-degree tip concentrates all the force into a pencil-thin line. It can cut wood, carve concrete and strip paint. For general cleaning, a wide white or green tip is safer, and the black soap tip applies detergent at low pressure.