Limestone in bathroom

Does limestone really work in a bathroom?

That is the first question almost everyone asks, and it deserves a straight answer: yes. Limestone has been laid in bathrooms, baths and thermae for two thousand years. It stands up to water. What separates stone from ceramic tiles is not durability but the fact that stone is a living material — it wants the right treatment at installation, and after that it looks after itself for decades.

The worries are usually about stains, wear and the stone being porous. We go through all of that below. But start with what weighs heaviest: a limestone slab is coloured through, all the way. There is no surface layer to wear a hole in. It only becomes more itself.

Limestone and underfloor heating

Stone is made for underfloor heating. It stores the heat efficiently and distributes it evenly, so the floor stays warm long after the heating has been switched off. Limestone works with both water-based and electric underfloor heating.

Just one thing: wait four weeks after laying before you switch the heating on. The adhesive and the impregnation want to cure in peace first.

Honed, brushed or diamond milled — which surface suits a bathroom?

Our feet and hands are among the most sensitive parts of the body. A material that looks the same to the eye can feel completely different underfoot. Several of our limestones come in different surface finishes, and the choice is as much about feel as about looks.

• Honed — smooth and soft, matte without being glossy. The most common surface in bathrooms and the one that shows the veining of the stone most clearly.
• Brushed — a touch rougher, with a texture that brings out the natural character. Many choose it where they want a little more grip underfoot.
• Diamond milled — rawer and lighter in tone, a Nordic and pared-back character.

There is no right answer. Order samples, stand them in the bathroom and see how they feel — both in daylight and under the lamp that is actually going to hang there.

Elingstrand honed in a bathroom

How stone works in a bathroom

Stone is a living material. It breathes, it takes up and it gives off — and it does so both upwards and downwards. Once you understand how it works, the rest is simple. It is mostly a matter of doing a few things in the right order, and then letting stone be stone.

From below: the moisture and the heat

Beneath the slab there is a substrate, and in a bathroom there is water. Limestone is porous enough to let moisture migrate through it — it is the same property that makes it feel alive underfoot. Underfloor heating drives it on: the heat makes the moisture move upwards, through the stone rather than around it. On the way it brings salts with it out of the substrate, and they show at last on the top as pale efflorescence or a yellower tone.

There is nothing wrong with the stone and it is no argument against underfloor heating. It is simply how the material behaves, and it is easy to meet — but it has to be done before the slab is in place.

Three things, all of them before laying:

• A dry substrate. Levelling compound and concrete must have dried properly, below 90 % moisture content. The drier the start, the less to deal with afterwards.
• The right adhesive. Ardex X32 is made for natural stone and binds the moisture quickly. Ordinary adhesive often contains plastics and chemicals that can in turn migrate up into the stone. That is exactly why we have chosen X32, and our guarantees are based on it.
• VERNA Pre-Protect on the underside and edges. The impregnation seals the pores from below, so the moisture stays where it belongs.

Pre-Protect is not needed in the whole bathroom. The floor and walls of the shower area, plus a stretch beyond it — that is where the water actually stands.

While the stone is being laid

Three things are worth knowing for whoever lays the floor.

The grout can stain. A porous surface readily draws in pigment from the grout. Impregnate the top before you grout, and the grout stays in the joint. Both Pre-Protect and Protect do the job.

This applies to limestone and marble with porous surfaces: Alevik honed and Rosenthal sand beige matte honed, as well as all the diamond milled varieties — Kolmården marble diamond milled, Ekeberg marble diamond milled, Boo marble diamond milled, Red Öland limestone diamond milled, Öland limestone Chateau Selection and Red Jämtland limestone diamond milled. Unlike Pre-Protect from below, this applies to the whole surface, in every space.

Leave the tape alone. Not even for a short while when painting. Tape leaves marks in the stone that are stubborn to get out. This is the thing we are asked about most often after the event.

Remove adhesive and grout residue straight away. Clean the whole surface with VERNA Deep Clean once the grout has cured. Anything left behind is otherwise built in under the protection.

From above: everyday life

Once the floor is down, most of the work is done. The basic protection upwards is VERNA Protect over the whole surface after grouting — a thin, even coat. If the stone is absorbent you apply a second one at the earliest forty-five minutes after the first. Let it dry for twenty-four hours before the bathroom is put into use.

After that there are three things that meet the stone every week.

Soap and shampoo. The residue gathers around the floor drain. Rinse the shower area down after showering — it takes ten seconds and is the single best habit you can give the floor. Choose an acid-resistant drain grate as well, that is, one that does not give off acid to the stone.

Make-up, oil and grease. Protect keeps the pores closed, so the stain settles on the surface rather than in the stone and can be wiped away. If it does stay, VERNA Deep Clean takes care of it. Rubber, glue, candle wax and marker pens are first carefully scraped off, after which thinner, white spirit or turpentine dissolves the rest.

The cleaning. Here there is one single thing to remember: nothing acidic. Vinegar, lemon and limescale remover etch the surface matte, because limestone is alkaline. VERNA Daily Clean is made for natural stone and is quite enough. Gentle on the stone and on the drains.

The water test

We are not asking you to re-impregnate the floor every year as a matter of routine. The need depends on how the surface is used, and a treatment that is not needed does no good.

Do this instead, once a year:

Pour a little water on the stone and see what happens. If it stays there as a bead on the surface, the protection is intact — then you do nothing. If the water is drawn in, it is time for a new coat of Protect.

The same test works right after an impregnation, to see whether the surface has become saturated. If the water beads, you are done.

In short, in order

1. Dry substrate, fall towards the drain
2. Pre-Protect on the underside and edges — the shower area plus a stretch beyond it
3. Porous stone? Impregnate the top before grouting
4. Lay with Ardex X32, grout with Ardex G10, seal with Ardex ST
5. Deep Clean once the grout has cured
6. Protect over the whole surface, let it dry for twenty-four hours
7. Underfloor heating on at the earliest four weeks after laying
8. Daily Clean in everyday life — and a water test once a year

The impregnations are applied between +5 °C and +35 °C. Always test on a slab out of sight first.

Stains and patina — the difference

A stain can be removed. Patina is something else — and something you will come to like.

A scratch in the floor usually needs nothing done about it — it wears away over time and adds character. If acid has etched the surface, you can gently sand by hand with a fine diamond sanding block, steel wool or a nylon pad.

The stone will change, and it should. Where ceramic with a printed surface layer grows dull, natural stone goes the other way — the veining comes forward, the colours deepen. Much like a leather sofa or a solid wood floor. The never quite perfect but genuine. The kind of thing the hand feels.

Start with samples

Stone cannot be chosen on a screen. The light in your bathroom, the tiles you already have, the brass on the mixer — all of it affects how the stone reads.

Order samples in the 20×20 cm format. Buy three and you get 10 % off. Lay them on the floor in the room in question and look at them over twenty-four hours, in daylight and in lamplight.

Frequently asked questions

Can limestone be laid over underfloor heating?
Yes, both water-based and electric. Wait four weeks after laying before you switch the heating on.

Do I have to impregnate?
Yes. Pre-Protect on the underside and edges in the shower area before laying — that stops moisture migration from below. Protect over the whole surface after grouting — that protects against soap, make-up and oil from above. If the stone is porous, the top is impregnated before grouting as well, so the grout colour does not take hold.

How often do I need to re-impregnate?
Only when needed, not as routine. Do a water test once a year: pour a little water on the stone. If it stays there as a bead, the protection is intact. If it is drawn in, the floor needs re-impregnating.

What actually is moisture migration?
Water gathers beneath the slab, the underfloor heating warms it, and the moisture rises as vapour through the stone rather than around it. On the way it takes salts with it that show as white efflorescence or a yellowed tone on the top. It cannot be put right afterwards — which is why the protection is done before laying.

Does limestone get slippery?
A honed surface is smooth but not slippery in the way glossy ceramic tiles are. If you want more grip, choose a brushed or diamond milled surface.

How much stone should I order?
The area plus 15 %. Later orders can differ in shade, since the stone is quarried block by block.

How large a share of the bathroom budget is the stone?
Four to five per cent, as a rule. Most of what a bathroom costs to build goes on work that is not visible afterwards.

Can I lay the stone myself?
The floor in a wet room is to be laid by a certified tiler in accordance with industry rules. The preparation — fall towards the drain, a dry substrate below 90 % moisture content — is decisive.

What happens if I use ordinary adhesive?
It can migrate up and discolour the stone from within. That is why our guarantees are based on Ardex X32.

Bring nature indoors

Which stone suits your particular bathroom comes down to the light in the room, the format and the feeling you are after. All stone has its very own character. Every pattern, texture and surface is unique.

See the whole limestone range or our marble, and order samples of the ones you take to.