Pressure washers are cheap, satisfying and genuinely useful, which is exactly why they cause so much expensive damage. Almost everyone who has ruined a patio, a fence or a rendered wall did it with good intentions and a machine that felt like it was working brilliantly at the time. The problem is that most pressure damage is invisible for weeks. This guide is not an argument against pressure washing, which we use every week on the right surfaces. It is about knowing which surfaces punish it, how the damage happens and what to do instead.
Render: the most common and most expensive mistake
A lance held close to render removes the finish and drives water behind it. On thin-coat silicone systems the mark is permanent and visible in low sun forever. On older sand and cement render, water forced through crazing accelerates the loss of bond and can turn a cosmetic problem into a blown patch needing re-rendering. Softwashing does the job with no risk.
This guide sits under our Pressure Washing work, covering 20-mile radius of Plymouth.
Roof tiles: stripping the surface you need
Concrete tiles have a dense surface layer that keeps them shedding water. Blast it off and the tile becomes more porous, holds more water, and grows moss faster than before, so the dramatic instant result actively shortens the interval to the next problem. Water forced under laps ends up in the loft, and ridge mortar goes with it.
Soft natural stone paving
Indian sandstone, limestone and riven slate all mark under a close lance. The damage shows as a pale, slightly pitted band exactly where the operator's arm swept, visible whenever the sun is low. Slate can delaminate in sheets. The safe approach is a treatment first, then even coverage from a rotary cleaner at moderate pressure, tested in a corner.
Timber decking and fencing
Wood is fibrous and pressure lifts the fibres, leaving a furry surface that holds water, greys faster and takes stain unevenly. Softwood fence panels can be perforated outright. Once fibres are raised the only remedy is sanding, which is not practical on a whole deck. Gentle washing along the grain, or a treatment, is the correct route.
Pointing, lime mortar and old brickwork
Mortar is deliberately weaker than the units it joins. A pressure washer removes it very efficiently, and repointing a wall costs many times what cleaning it does. On listed and older properties with lime mortar, this is not a maintenance problem but a conservation one. Masonry with growth needs a biocidal approach, not force.
uPVC, seals and glazing
Plastic scratches, seals get lifted, and water driven past a window gasket or a conservatory glazing bar appears indoors later. Trickle vents and soffit vents let water straight into the fabric of the building. Around glazing, low pressure and a brush is not a compromise, it is the correct method.
Cars, meters and everything else in the way
Less dramatic but very common: paintwork stippled by overspray, electric meter boxes filled with water, air bricks flooded, vents forced open, and neighbours' washing ruined. Preparation is a real part of the job. If someone starts washing without moving or covering anything, the damage bill is not limited to the surface being cleaned.
Using a pressure washer sensibly
If you do use one, keep a wide fan tip, stay well back, keep the lance moving constantly, never aim upwards under a lap or a cill, test in a hidden area and stop the moment you see the surface changing. Reserve it for concrete, block paving and similar. For everything else, a treatment and patience produces a better result with no risk.
Questions we get on this
- Is pressure washing ever the right choice?
- Yes, on concrete, block paving and similar hard non-decorative surfaces, ideally with a rotary cleaner for even coverage.
- How can I tell if my render has been pressure damaged?
- Look along the wall in low sun. Lance marks appear as bands or arcs of slightly different texture and shade that no cleaning removes.
- My decking went furry after washing. Can it be fixed?
- Raised fibres only come back down with sanding, which is rarely practical over a whole deck. Future cleans should be gentle and along the grain.
- Do you ever pressure wash walls?
- No. Walls, roofs, cladding and glazing are softwashed. We reserve pressure for hard landscaping.
Related reading
- Keeping windows clear between professional visits
- Stopping moss and algae coming straight back
- Looking after render through a Devon year
- How often each part of your house needs cleaning