FAQs about flagstone floors

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Installation of flagstones

General FAQs

Installation of flagstone floors

Maintenance of flagstone floors

Laying patterns for flagstones

Oak FAQs


What size of notched trowel should I use?

Tilling trowels come with different sized notches in them. For laying larger natural stone flagstones you should not use anything less than a 10mm trowel, but many people prefer to use a 20mm notched trowel because it gives them a deeper bed which is more forgiving.

Do I seal the flagstones before laying them ?

No, lay the flagstones, then seal, then grout, then seal again. You may want to clean the stone before sealing the first time with a suitable stone cleaner.

All natural stone must be sealed. Sealing the stone is part of the installation process and all our stone is supplied unsealed. There are many different stone sealants on the market and every one will have a different effect on stone and that effect will be different depending on the type of stone. All our displays are fully sealed so you know what the floor will look like when it is completely finished. All photos on the website are of sealed floors too so you are getting a good indication of the finished look within the limits of photography. We strongly advise visiting our showrooms to view the stone for real however. We stock 2brands of sealant and all our displays are sealed with one of these. The first brand is a standard solvent based impregnator sealant; this has the general effect of darkening the raw stone by a few shades and also will highlight the inherent characteristics of the stone that can include veining and fossil content. The second brand is known as a clearseal; is rapid drying and has a minimal effect on colour & characteristics, again, depending on the stone.

What colour grout should I use ?

There are plenty of grout colours available, but we would suggest using slightly darker colours in areas that attract more dirt such as kitchens, or porches and boot rooms.

Can stone tiles be applied to timber floors?

Yes. Strengthening the floor with plywood is often advisable when fixing stone floor tiles. A flexible floor tile adhesive and floor tile grout must be used to fix floor tiles. Make sure that the floor does not flex under the weight of the tiles, depending on which type of floor tile i.e. travertine tiles, marble tiles, limestone floor tiles it’s best to calculate the weight for the right type of floor tile.

I have removed an existing parquet floor which is covered with bitumen can I tile on top of it ?

The official answer is no, you should try to remove as much of the bitumen as possible. Then you need to prime the floor with a latex smoothing compound.


How do I firm up my timber floor ?

It may be advisable to completely replace your timber floor before laying natural stone, other less drastic measures include replacing a few wobbly floorboards and ensuring there is no movement in the boards, simply by screwing the boards down. You may consider covering the floor completely with 12.5mm or even 17.5mm plywood or blockboard.

Is there a special adhesive to use on timber?

Yes, when tilling over a timber floor you must use a flexible adhesive specifically designed for use with timber.

Does a floor have to be level to fix stone tiles to?

Yes, although minor bumps and hollows can be leveled by applying more or less floor tile adhesive. A dry level screed is ideal for laying stone flooring. The floor must be clean, dry and grease free before laying any stone floor tiles.

How flat does my substrate need to be?

The flatter the better, you certainly don’t want any high points. but you can overcome any dips with the aid of a levelling compound, or by building the area up with additional adhesive.

Which Levelling compound should I use?

If you are working in an area which might get wet perhaps outside, or on a floor with no damp proof membrane (dpm), or your levelling compound will be below the dpm you should use a latex based levelling compound. Otherwise there are a selection of water based levelling compounds to use which can be used to build up areas from 1.5mm upto 40mm or more with the addition of aggregates. Note: before putting levelling compound on a concrete floor you should prime the floor with an acrylic primer to avoid bubbles forming in the compound, caused by air escaping from the concrete.


Is under floor heating possible with stone tiles?

Yes, stone is an ideal conductive surface for under floor heating. Floor tiles and stone tiles will allow the heat to rise naturally.

I have a wet underfloor heating system, does this require any special treatment ?

Yes, there are several things you need to do before laying your stone. If the screed has just been laid it will need to dry out thoroughly to prevent any moisture being absorbed into the stone which could cause it to discolour especially after you have sealed the floor which will trap the moisture. Suggested drying times vary from one day per millimetre depth of screed or a week per inch – typically 3 or 4 weeks. After the drying time you need to heat your floor up to full running temperature gradually over the period of a week, then run it at full temperature for a week before turning it off and allowing it to cool, this takes another week. When you do this the concrete slab will develop hairline cracks, which allow for expansion in the future when your underfloor heating is working. You must also use a flexible adhesive and grout. If you do not have the time available you can use a decoupling mat which will allow you to lay your stone one week after laying the concrete and without the need of cycling the heating system.

I will be fitting electric underfloor heating, does this require any special treatment ?

Yes, it is always advisable to use a thermally insulating backer board underneath your cables, this will prevent the heat produced from being absorbed and lost into the concrete slab, if you are tilling on a bathroom floor you will also, benefit from the boards waterproof qualities. You will then need to cover the cables to prevent and potential damage during tilling, you can either do this with flexible tile adhesive or a latex levelling compound. you must ensure there are no air pockets around your cables as this will cause hot spots and eventually a fault with the cable. You must also use flexible adhesive and grout.


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