Pressure washing a driveway: what to expect

What comes off

Green algae, black spot lichen, moss between the joints, general road grime and most of what has washed off the car over the years. Block paving usually comes back several shades lighter than the owner expects, because the change happens slowly enough that you stop seeing it.

We use a rotary surface cleaner rather than a bare lance. It keeps the pressure even, which is what stops the striping you see on drives washed with a wand held by hand.

What does not

• Old oil that has soaked into concrete. It lightens, it does not vanish.
• Staining from a rusted skip or a leaking planter, which has usually gone into the stone.
• Cracked or sunken blocks. Cleaning makes those more visible, not less, and we would rather warn you first.
• Colour loss on concrete slabs that have simply aged. Clean is not the same as new.

The sand, which people forget

Washing block paving takes the kiln-dried sand out of the joints along with the moss. If it is not replaced, the blocks start to move and weeds come back faster than before. Re-sanding is part of the job for us, not an extra line on the bill.

What it costs and how long it takes

A small driveway for one or two cars starts at £80, a large one for three or more at £130, and a patio at £70. Most drives are a half-day. We need an outside tap or a nearby water point, and it is worth moving the cars off before we arrive.