Kerb, Edging and Cobbles

There is no difference in the product, only the spelling. Kerb is the British spelling and curb is the American one, and both describe the raised stone or concrete edge that separates a road or driveway from a pavement, verge or border.

The cheapest edging we sell is a row of 10x10cm natural stone cobbles bedded and haunched in concrete, which works out at around £5 per metre for the stone. Kota Black limestone cobbles are the lowest priced at under 50p each, with Kandla Grey sandstone close behind. Add a bag of Postcrete or a small load of ST2 concrete for the bed and haunch. 

The 3 inch rule is a rule of thumb for how much concrete an edging needs to stay put: bed the kerb or cobbles on at least 3 inches (75mm) of concrete and haunch the same depth of concrete behind them. An edging held in less than that works loose under tyres within a couple of winters. The same figure turns up in two other places. For gravel, the edging should stand about 3 inches above the finished surface so the stone stays in. For lawns, a 3 inch deep trench between grass and border gives a clean edge that a mower can run along. It is guidance rather than a standard, but it is what most landscapers work to.

Kerb stones and cobbles are set on a wet concrete bed, tapped down to a string line and then haunched with more concrete behind them. Dig a trench about 150mm wider than the stone and deep enough for 75mm to 100mm of concrete under it. Run a tight string line at the finished height, lay a bed of ST2 or Gen 1 concrete, set each stone on it and tap it level with a rubber mallet, keeping joints even. Once a run is set, pack concrete behind the stones to within 50mm of the top and slope it away. Leave it 24 hours before loading the edge or laying paving against it, then joint the gaps with mortar or Joint-It. 

A standard British road kerb is 125mm wide, 255mm deep and 915mm long, and the smaller edging kerbs used on paths and drives are typically 50mm by 150mm in the same 915mm length. 

Strictly, a cobble is a naturally rounded stone and a sett is a cut, squared block, but in the paving trade the two words are now used for the same thing. Everything in our range is a sett by the old definition: a cut block with hand-dressed edges that sits flat and square, which is what you want for an edging or a driveway surface. Our natural stone cobbles are 30mm to 50mm thick in Silver Granite, Kota Black limestone and Kandla Grey or Fossil Mint sandstone, and the porcelain cobbles are 20mm thick with sawn edges.

Cobbles work better for a gravel path or garden drive, and a full-height kerb only earns its place on a drive that takes regular vehicles. A row of 20x10cm cobbles set in concrete and standing 25mm to 40mm above the gravel holds the stone in, follows curves easily and looks softer than a concrete kerb. For a straight, modern line, our 20mm porcelain edging strips laid on edge do the same job in grey, white or anthracite. 

Yes. Natural stone cobbles do the same job as a concrete edging strip once they are bedded and haunched in concrete, and they look better doing it. For a driveway edge choose granite, which is the hardest of the three stones and shrugs off tyre scuffs. For paths and patios, limestone or sandstone cobbles are fine and match our paving of the same name. A stone edge costs a little more per metre than a plain concrete strip, but it is thicker, it can be laid in curves, and it will not chip and show grey concrete underneath.