Frequently asked questions

Start from where the stone goes rather than from how it looks. Exterior surfaces are governed by water absorption and freeze behaviour, floors by traffic and abrasion, countertops by staining and heat, and cladding by flexural strength at the anchor points. Once the exposure is defined the shortlist is usually short. Tell us the position, the climate and the traffic level and we can narrow it with you.

Both. Polishing closes the surface and makes it easier to clean, but also more slippery when wet and quicker to show wear on a busy floor. Honed, brushed and bush-hammered finishes give more grip and hide scratching, at the cost of some depth of colour. Outdoors a more open finish holds more water, which matters wherever freezing is a factor.

Consistency comes from batching, not from the stone name. Material from one quarry run, sorted together and reserved for the project, will match; the same name bought in two lots months apart often will not. So the quantity for the whole scope — including cutting waste and a spare allowance for later repairs — should be settled before production rather than topped up afterwards.

On its own, very little: grade names are not standardised between quarries, factories or markets. What makes a quality level enforceable is an approved physical sample retained by both sides, plus written numeric tolerances for thickness, calibration, flatness, finish and permitted natural features. Ask for those numbers rather than for a grade word.

Slabs are classified after sawing and finishing by colour, vein character, texture and surface quality, and a batch is then set aside for the project so the visual range on site stays inside what was approved. Because grading vocabulary varies between suppliers, the sorted batch matters far more than the label attached to it.

Read more — Building stone grading and sorting

Published test methods exist for the properties that matter — absorption and density under ASTM C97, EN 13755 and EN 1936, strength under ASTM C170, ASTM C99, EN 1926 and EN 12372 — and a specification can call any of them up. A report describes only the batch it was cut from, so if you need figures for your own material, say so in the specification and we will set out who tests, on which batch and at whose cost.

Fixing method and, on facades, the anchor design; joint width and layout; an adhesive or mortar suited to the stone, since some light stones stain from the bed; whether edges and cut-outs are prepared in the factory or on site; the laying sequence against the sorted batch; and protection of finished surfaces while other trades are still working.

With neutral-pH cleaners, always. Acidic products etch calcareous stone such as marble and travertine, and strongly alkaline ones can dull a polish. Spills should be lifted rather than spread, because porous stone absorbs rather than repels. Whether sealing is needed, and how often it is renewed, depends on the porosity of the stone, the finish and the exposure.