Debi Boulton, brand manager lat Dunlop Adhesives looks at common pitfalls often associated with natural stone tiling.
Tiling with natural stone is a matter of knowledge and balance; the knowledge to identify the variables that can affect the overall adhesion, and the ability to get the right balance between the stone, the background substrate, and the adhesive. It can be tricky, so it’s a good idea to make sure that you fully understand the materials being used so that the perfect adhesive and grout is selected for the job.
The first consideration should relate to the type of natural stone that is being used. Some carbonate-based stones, such as marble, travertine and limestone, may be susceptible to drawing in residual moisture from the tile adhesive, which has the potential to cause a few problems! If this happens there is a strong risk of the stone being stained or watermarked. Furthermore, excessive residual moisture has the potential to react with certain minerals (such as iron oxides) and organic deposits in the stone, which could discolour the face of the tile.
To prevent such an occurrence, merchants should recommend that tradesmen use a specialist rapid-setting, low water demand adhesive. This will act to chemically bind any excess water safely within the adhesive bed – virtually eliminating the risk of either the stone being stained, or the discolouration of the tile face. Indeed, as is the case with all tiling jobs, the choice of the adhesive and grout to use with natural stone tiles is absolutely paramount in terms of being able to guarantee the longevity of an installation – whether a new build or refurbishment.
However, merchants should advise that before any adhesive is used, it is vital to make sure that the base substrate is the right one for the conditions to which the tiling will be exposed. For example, for a wet duty application in a bathroom, a water resistant background is required. In all cases, the background substrate must be stable enough to receive a rigid finish, but if there will be sporadic exposure to water (as there would be in a bathroom) then dimensional stability to changing moisture conditions becomes even more important as a means to avoid the generation of significant moisture expansion and contractions.
Similarly, the rigidity of the substrate must extend to the ability to support the (often substantial) weight of the stone tiles, and indeed the added weight of people walking upon it without excessive movement and deflection. Sometimes such unwanted movement might occur if the stone has not been sufficiently bedded in to the adhesive, either because of an uneven base substrate, or indeed an uneven tile surface – both of which could create troublesome voids between the layers.
Overall, there’s a lot for builders’ merchants to consider! But if you can remember to advise using a rapid-setting, low water-demand adhesive, and to judge each job on its relative material merits, then there is no reason why merchants can’t boast natural stone tilling know how!