Living With Stone Indoors

Every stone showroom is arranged to make you choose with your eyes. Polished slabs, dramatic veining, lighting angled to make marble glow. The decision that will actually determine whether you are happy in five years is printed on a technical sheet nobody hands you: water absorption by weight.

The number that predicts everything

Below 0.5 per cent, a stone is effectively closed. Granite, quartzite, dense basalt, some porcelain-grade limestones. Wine sits on the surface. You can use them in a kitchen without vigilance.

Between 0.5 and 3 per cent you are in the territory of most limestones and marbles. They will take a stain from oil, wine and lemon, and they will develop a patina that many people love and some people find intolerable. This is a personality test, not a quality question.

Above 3 per cent, in a wet or greasy environment, you are choosing maintenance as a lifestyle.

Honed, brushed, polished

Polished stone is a mirror: it shows the room, doubles the light and looks spectacular for exactly as long as it stays unscratched. On a floor, in a house with sand outside, that is roughly one season.

Honed is matt, uniform and forgiving. Brushed, or leathered, has a slight texture that hides both scratches and water marks and grips underfoot, which makes it the sensible choice for a floor that continues outside.

For a threshold running from a living room to a terrace, the correct specification is usually the same stone, honed inside and brushed or flamed outside. Same colour, same joint, different friction.

Choose the stone you can live with dirty. Every stone is beautiful clean.

Giorgio Pace, stone merchant, Verona

Sealers, honestly

An impregnating sealer slows absorption. It does not stop etching, which is a chemical reaction between acid and calcium carbonate, not a stain. Anyone who tells you their sealer prevents lemon marks on marble is selling a product they have not tested.

Applied properly, a good impregnator buys you time to wipe a spill. That is the whole claim, and it is worth having.

Getting the joints right

Nothing separates a good stone floor from an ordinary one like the joint. Most disappointment comes down to three decisions made on site by somebody who was never asked.

Joint width first: 2 to 3 millimetres for a calibrated modern stone, wider only if the material genuinely requires it. Then grout colour, which should match the darker tone within the stone rather than the palest one, because grout lightens as it cures and a pale joint turns a floor into a grid. And finally the layout, which somebody has to set out from the most visible line in the room, usually the threshold or the axis of the main opening, rather than starting in a corner and letting the cuts land wherever they fall.

Ask for a dry lay of one bay before anything is fixed. Twenty minutes of standing and looking will save an argument that cannot otherwise be settled.

Underfloor heating and the thickness question

Stone and underfloor heating belong together: the material conducts well, holds heat and stays comfortable underfoot at surface temperatures far below what a radiator needs.

Two numbers govern it. Thickness, because a stone above about 25 millimetres slows the response of the system to the point where it can no longer follow a day, and thermal resistance, which should stay below roughly 0.15 square metre kelvin per watt for the floor build-up as a whole.

Also: tell the fitter it is a heated floor. The adhesive, the movement joints and the commissioning cycle are all different, and a floor laid without that knowledge will crack along a line nobody can explain later.

The case for using it anyway

None of the above is an argument against stone. It is an argument for choosing with the eyes open, because the alternative, an engineered surface that never changes, has a quieter cost.

A limestone floor at twenty years is smooth where people walk, darker in the doorways, and faintly cupped in front of the sink. It records the house. Nothing manufactured does that, and no photograph of a new floor tells you which one you will want to live on.