Summer garden parties are in full swing, so it’s no mystery that so many Brits are whipping out the pressure washer to give their patios a good clean. This was reflected in a recent surge in online searches for "pressure washing", spiking by more than 64,000 in the past month alone.

However, according to patio specialists, this enthusiasm, coupled with a lack of expertise, could come at a heavy cost. Alex Essex, Managing Director at The Patio Black Spot Removal Company, warned: “Replacing patio tiles that have been damaged by improper pressure washing can be a costly exercise.” In fact, their study shows that early two in five homeowners are making critical mistakes with pressure washers, leading to extensive and expensive damage.

Natural stones such as sandstone and limestone can be particularly susceptible to damage from excessive water pressure, making them poor candidates for indiscriminate blasting.

Alex highlighted the financial impact of overlooking proper technique: “Laying a new patio now costs a minimum of £125 + VAT per square metre for materials like Indian Sandstone or flagstones, and this can rise to as much as £300 per square metre for premium options such as granite or York Stone.”

According to the expert, for the average 30-square-metre patio, this could cost about £4,500 including VAT, “covering the necessary ground preparation and installation.”

How to pressure wash your patio safely

First of all, you want to identify what your patio is made from before reaching for the pressure washer. Softer stones in particular are vulnerable and some can’t tolerate high pressure at all.

“Sandstone, limestone, granite and marble each have different strengths and weaknesses,” Alex pointed out.

Always choose a washer with an adjustable PSI. For most surfaces, aim for between 1,200–1,800 PSI, as going above this can cause damage, especially to natural stone.

A wide or fan nozzle (25–40 degrees) is recommended instead of a pinpoint jet to help reduce the risk of etching or chipping.

Begin with a small spot, so you can check for any unexpected damage or discolouration before treating the full patio. Maintain a distance of 12 to 18 inches from the surface and keep the nozzle in motion.

“Never concentrate the jet on one spot for too long,”  highlighted Alex.

Then, you can start from the highest point of your patio and clean in sections, overlapping your strokes to prevent streaks.

Avoid spraying directly into joints between stones. If sand is washed out, allow the surface to dry and refill the gaps as needed.