Guides

Nine Pressure Washing Mistakes That Cost Real Money

1. Pressure washing a roof

The most expensive mistake available. It strips the protective granules from asphalt shingles, shortens the roof's remaining life by years, and voids most manufacturer warranties. The streaks return anyway, because they are algae and the pressure did not kill it. Roofs are soft washed or left alone.

2. Aiming up under siding

Siding overlaps downward to shed water. Spraying upward drives water behind the panels, into the wall cavity and the insulation. It does not show for weeks, and then it shows as damp, mould, or rotted sheathing.

Always work top down and angle slightly downward. Never point a jet up into a seam, a soffit vent or a window head.

3. High pressure on windows and seals

Double glazing units are sealed at the edge. Force water at that seal and you can breach it, and a breached unit fogs permanently and has to be replaced. Older timber windows leak straight into the room.

Windows get rinsed, not blasted.

4. Across the grain on timber

Tears the fibres, raises the grain, and leaves a furry surface that holds dirt and looks worse in a year than before you started. Always along the grain, one board at a time, at low pressure with a wide tip.

5. Using a zero degree tip on anything

The red pencil jet engraves concrete, gouges timber, strips paint in a stripe and can cut skin. It has almost no legitimate use in exterior cleaning and it is behind a large share of permanently marked surfaces.

6. Ignoring soft mortar

On older buildings the mortar is lime based and deliberately soft. Pressure removes it, and the small pile of sand at the base of the wall is your building's mortar. Water then gets behind the brick face and takes it off over the following winters.

Test a joint with a key first. Soft joint means soft wash.

7. Skipping dwell time and compensating with pressure

The most common professional shortcut. Biological growth needs a cleaning solution and time. Skip the time, and the only lever left is more force, which is how surfaces get damaged and why the algae is back within a year. Patience is genuinely the technique.

8. Forgetting the plants and the runoff

Cleaning solutions will kill planting. Pre wet everything nearby, cover what you can, and rinse thoroughly afterwards.

Runoff matters too. In many jurisdictions letting waste water carrying detergents or hydrocarbons run into a storm drain is an offence, and in commercial work it is taken seriously. Containment is part of doing the job properly.

9. Forgetting you have neighbours

This is the one that turns into an argument. Overspray from a balcony or a shared wall lands on someone else's car, windows, laundry or terrace furniture. In dense housing and apartment blocks, containment and simply knocking on a door first prevents most of it.

Early morning commercial frontage work has the same issue in reverse: noise. A petrol machine at 6am under a bedroom window is a complaint waiting to happen.

The one question that catches most of it

Before anything is cleaned, ask: does this surface want force, or does it want chemistry?

Concrete, stone and paving want force. Roofs, siding, render, old masonry, timber and anything painted want chemistry. Getting that single decision right avoids almost every expensive outcome on this list.