How to clean block paving without damaging it

Cleaning block paving is one of the few driveway jobs that is easy to do badly and expensive to undo. Get the pressure wrong and you are not cleaning the blocks, you are washing out the jointing sand that holds them together, and that is how a clean driveway turns into a wobbly one within a year. Our driveway cleaning page covers when it is worth paying someone.

I get called out more often to fix a bad clean than to fix a dirty driveway. Here is what I would actually do, in the order I would do it.

What actually damages block paving when you clean it

It is almost never the washing itself. It is the pressure. A domestic pressure washer on a narrow turbo nozzle, held too close, will lift jointing sand out of a block paving driveway in minutes. Once that sand is gone the blocks lose their interlock, and interlock is the entire structural idea behind block paving. Loose blocks, rocking corners and weeds coming back within weeks are all downstream of the same mistake.

The right way to clean block paving

• Sweep first

  Loose grit and leaf litter will scratch the surface if you blast them around instead of clearing them first. Two minutes with a stiff broom before the washer comes out.

• Use a wide fan nozzle, not a turbo nozzle

  A 40-degree fan spread over the surface at a sensible distance cleans without concentrating enough force in one spot to dig out the joints.

• Keep the lance moving and at a distance

  Roughly 30cm off the surface, working in overlapping passes, rather than holding it still over one area.

• Work with the joints, not straight at them

  Angle the spray so you are cleaning the block face, not firing directly down into the gaps between blocks.

• Rinse from the highest point down

  So dirty water runs off the driveway rather than back across a section you have already done.

Re-sanding the joints, the step everyone skips

Even a careful clean pulls some sand out of the joints, and this is the step most people never get to. Once the surface has dried properly, usually a day in decent weather, brush kiln-dried jointing sand into every gap until it is level with the top of the blocks, then give it a final light sweep so nothing sits proud on the surface.

What not to use

If any of these have already been used on your drive, driveway repair covers what can be put right. Skip the wire brush, it scores the surface of the blocks. Skip bleach and strong acid-based cleaners on anything other than a stubborn algae patch, and even then dilute it properly and rinse thoroughly, because run-off into a border kills plants and run-off into a soakaway is not something you want either. And skip the narrowest nozzle setting on the pressure washer entirely. If the driveway needs that much force to come clean, the problem is not the dirt, it is that something underneath has already failed.

When to call someone instead of doing it yourself

If blocks are already rocking, if whole sections have sunk, or if weeds are coming back within days of clearing them rather than weeks, that is not a cleaning problem. That is the base underneath the paving moving, and pressure washing it again will not fix it. That is a job for someone who can lift the affected area, sort what is underneath, and relay it, which is a different job to a clean and worth pricing separately rather than bundling into a cleaning quote.

Driveway cleaning cost for a straightforward professional clean and re-sand on a typical two-car block paving driveway is usually a few hundred pounds depending on size and condition, and it is worth it once a year or two rather than letting weeds and moss get established. If you would rather have someone do the whole job properly, including checking the joints and the edges while they are at it, our driveway cleaning page has the detail, or see our block paving page if the driveway needs more than a clean.

If the drive still looks tired after a proper clean and a re-sand, the problem is usually not dirt. The signs your driveway needs replacing covers how to tell a surface problem from a structural one, and the weeds guide explains why full joints are what keeps it clean in the first place.