Laying Natural Stone Tiles

Natural stone tile problems

Whilst natural stone tiles are probably better left to professionals to fix, due to the cost and the inherent risks of cutting and laying. It is not beyond the capabilities of the competent do-it-yourselfer to produce a beautiful job.

If you are installing over a concrete substrate the potential extra weight of natural stone will not be a problem, if laying over boards you must check that the stone + adhesive are not going to be too heavy. On gypsum plasterboard the weight per square metre must not exceed 32 kg, which approximates to a 10mm thick tile. Other job specific boards such as tilebacker and glass reinforced cement boards should cope with heavier weights, but always check with the manufacturer.

With natural stone there is always the risk of staining, particularly with limestone and pale coloured stones to reduce this problem wherever possible use a rapid drying adhesive, where solvent rather than water is the drying agent and less absorbance takes place. With light coloured stone white is usually the best adhesive colour.

Never ever use the old fashioned spot method of applying the adhesive; this always results in voids beneath the tile which is bad for all floor tiles but really bad for natural stone. A further possible problem with spot fixing is for the stone to show shading through from where the adhesive spots were applied. Using the appropriate notched trowel flat spread and then comb the adhesive to cover the entire tile.

Your biggest problem could be the grouting stage, where your beautiful looking natural stone floor is at mortal risk, especially if you have used a porous stone.
First of all search for a grout colour that matches the tile colour as closely as possible, you can try rubbing some dry grout into a joint to test the colour match, this will give you an indication of the final result. If the colour is a close match your problems will be limited.

Secondly sealing your tiles before grouting might not give you the totally natural look you were planning for, but will stop the grout colour migrating into the tile and forming a border shading around each tile.

The risk of migration can be mitigated by using rapid setting grout. Always avoid using grouts that contain any grey Portland cement.

Finally where movement joints are required it normally safe to use neutral curing silicone, but never use acid curing sealants especially with marble and limestone where the acidic chemicals can react with any natural carbonates within the stone. This is unlikely to be unsightly but could cause a bonding problem or dry joint.