Natural stone is heavy. If your base is solid you need not expect to have problems. Concrete is an ideal base to work with and you should ensure it has a damp proof membrane underneath. If the concrete is fairly new, make sure it is fully cured and completely dry.
If your floor is suspended on joists and boarded, or if your floorboards are worn unevenly or otherwise weakened, you may have to fix plywood panels to support the additional load. A high quality WBP plywood board at least 15mm in thickness, screwed down at 200mm intervals, will usually be suitable. Flexing wooden floors can often be rectified by adding more struts between the floor joists, strengthening the joists, or screwing down the floorboards, but it may be advisable to get advice from a professional builder if you are concerned about the structure. (see our article)
A Smooth Base
It is very important to have a smooth base. Minor irregularities of up to 3mm are absorbed within the fixing adhesive or mortar bed, depending on the product being laid; anything greater than that will either need drastic sanding down (timber surface) or rectification using a self-levelling compound (solid base).
The foundations and fixings may be out of site but they are vitally important to the long-lasting success of your investment and being natural stone, it will be long-lasting!
PLANNING and ORDERING
Planning your installation well will definitely save you time later on, so don’t skip this stage.
Sketch out a plan and double-check the measurements before ordering your materials. Remember to include some extra tiles in your calculations for cutting and filling in odd shapes around obstructions or at the corners of the room.
I strongly recommend that you over order by approximately 5% in order to replace any breakages you may have now or in the future and by 5% for wastage during laying. It cannot be guaranteed that any future order will come from the same batch of stone and therefore may look slightly different.
Check that you have the right tools for the job.
– A water-cooled diamond wheel cutter is recommended for accurate cutting.
– It is important that you use the right adhesive and grout for your chosen stone. Colours and specifications vary according to the material being used and your stone supplier will be able to advise on this and probably supply the correct adhesive and grout.
– Make sure the colour of the grout goes with the colour of stone that you are laying as you are going to have to live with it for some time!
– Different stones retain moisture at various rates and because the surfaces vary from rough with holes to glass smooth, it is very important to choose the correct mortar.
Underfloor heating works really well with stone flooring. Choose a good quality system and ensure its working before laying your stone floor. You wouldn’t want to have to lift the stone tiles up once they’ve been laid!
PREPARE THE SURFACE
Clear your room and prepare the surface. This could take a bit of time but if done properly will ensure your floor remains in top condition for a long time.
– Laying over a new concrete base:
Always allow sufficient drying time of new concrete and sand and cement screeds before starting. In the case of new concrete this should be a minimum of 6 weeks and about 3 weeks for screeds.
– Laying over an existing concrete base:
Clear out any old floor coverings. Brush off any loose or flaky concrete and chip off any bumps. If it’s not very flat at all you may have to put down a layer of self-levelling screed. Tiling a floor that’s not reasonably flat may cause the stone tiles to crack under load.
– Laying over an existing wooden floor:
Clear out any old floor coverings. Put down some plywood, at least 1.8cm thick, to counteract the flexing of the floorboards. Screw down the board with countersunk screws so that the heads don’t damage the underside of the new tiles. Seal the plywood before applying your adhesive.
– Skirting boards:
If possible, remove any skirting boards. Any blemishes made when cutting the floor tiles at the edges will be hidden by the skirting boards when you put them back.