Is pressure washing safe for block paving?

Block paving and pressure washing have a complicated relationship. Most of the damage we’re called to fix wasn’t caused by the bricks getting old — it was caused by someone hammering them with a £100 domestic pressure washer.

What goes wrong

A consumer pressure washer at 1,800 PSI on a focused jet will strip jointing sand out of block paving in seconds. Once the joints are empty, the bricks lose their lateral support, water gets underneath, the sub-base shifts, and the surface starts to sink or lift. The bricks themselves are usually fine. The problem is the joints.

How a pro does it

• Pre-treat with biocide so the chemical does most of the moss/lichen killing — not the pressure.
• Use a rotary surface cleaner with controlled pressure (typically 1,500–2,200 PSI) rather than a focused jet.
• Sweep, never blast — overlap each pass, keep the wand moving, never linger.
• Always plan to re-sand the joints after cleaning, with a polymeric sand like Nexus ProTitan that locks tight when watered in.

Signs your driveway needs re-sanding

• Bricks visibly sitting lower than the kerb or surrounding edge.
• Weeds growing along the joint lines (the sand has gone, soil has filled the gap).
• Bricks rocking under foot when you walk on them.
• Sand visible washed across the surface after rain.