Excessive pressure or the wrong nozzle angle can strip paint, etch soft timber, dislodge mortar between bricks, or force water behind cladding and into wall cavities where it can cause hidden damage that isn't obvious until well after the job is done.
Older or more fragile surfaces, aged render, weathered timber decking, painted brick, are particularly at risk if treated with the same pressure and technique used on durable concrete, which is why professional operators adjust pressure and distance based on the specific material.
If you're considering a DIY approach, testing on a small, inconspicuous area first and starting with lower pressure than you think you need is the safer path. For anything beyond a straightforward driveway or path, professional assessment of the surface first genuinely reduces the risk of an expensive mistake.
