What a new patio really costs per square metre

When someone asks us what a patio costs, the honest answer is between £165 and £230 per square metre, laid. That surprises people who have priced sandstone at £35 per m² at the builders’ merchant. The stone is only about a third of the cost. Here is where the rest goes.

Digging out and taking it away

A patio needs about 200 mm of depth below the finished level. On a 30 m² terrace that is six cubic metres of soil, roughly ten tonnes, which has to be dug, barrowed and taken away in grab lorries. Access matters: a straight run from the road is quick, a narrow side passage doubles the time.

The sub-base

This is the part you never see and the part that decides whether your patio is still flat in ten years. We lay 150 mm of MOT Type 1, compacted in two layers with a plate compactor. On clay we add a geotextile membrane first so the stone does not sink into the soil.

The mortar bed

Slabs should sit on a full bed of mortar, not five dots. A full bed stops rocking and cracking, and stops water collecting under the slab and freezing. It takes more time and more material, and it is the most common shortcut we see.

Cutting, jointing and falls

Every edge, step and manhole cover means cuts. Curves mean a lot of cuts. We set a fall of 1 in 60 away from the house so water runs off, and joint with a brush-in or pointed mortar depending on the stone.

A worked example

A 30 m² rectangular sandstone terrace in Oakham, with good access, came to £5,250: £1,150 for excavation and waste, £900 for sub-base, £1,050 for stone, £1,650 for labour on the bed and laying, and £500 for jointing and sealing. That is £175 per m².

If you want a quick range for your own garden, the estimator on our home page does the sums in a minute.