Technical
Can I fix large format tiles onto a partition wall?
As with all types of wall tiling, it must be ensured that the substrate is suitable to receive a tile finish and is correct for the type of conditions to which it will be exposed. It must be clean, dry and free from surface contaminants.
When fixing large format tiles it is essential to ensure that the background is sufficiently flat to enable good contact to be made between the tile and adhesive, without having to build up the bed of adhesive beneath the tiles. Generally, the maximum recommended thickness for ready mixed adhesives is 3mm, exceeding this thickness could result in the adhesive shrinking and cracking as water is lost during the drying process, weakening the bond strength of the adhesive. Cement-based adhesives are suitable for use up to 6-8mm, although it should be remembered that increasing the adhesive bed thickness will increase the weight which the substrate must support.
It must be ensured that the substrate is sufficiently rigid and capable of supporting the weight of tiling. A gypsum plaster finish coat is able to support a maximum weight of 20kg/m2; plasterboard 32kg/m2, tilebacker boards approximately 40kg/m2 (although the board manufacturer should be consulted for their recommendations).
It is possible to increase the weight limits of the substrate by fixing anti fracture matting with adhesive to the substrate and mechanically fixing the matting with stainless steel raw bolts and washers at 400mm centres vertically and horizontally through the substrate to the studwork/blockwork behind.
Boards should be screw fixed to supporting framework at maximum 300mm centres ensuring that all board edges are fully supported (check with tile backer board manufacturers for their recommendations). When tiling to plasterboard, jointing compound at board junctions should be primed with either Johnson Prime & Seal or Norcros Prime Bond.
Large format tiles can be cut in the same manner as smaller format tiles, however a floor tile cutter may be required for thicker gauge tile bodies.
When fixing large format tiles with ready mixed dispersion adhesives which dry by water loss, the drying time of the adhesive, especially towards the centre of the tiles, will be increased. This is because of the large surface area of the tiles and the fewer number of joints, through which moisture from the adhesive can escape, than would be present when using smaller format tiles. To prevent grout drying ‘patchy’ due to moisture trapped in the adhesive layer, grouting should be delayed until the adhesive has fully dried.
Ready mixed adhesives are suitable for use with tiles up to 300mm x 400mm, however where larger tiles are to be fixed, cement-based adhesives, which dry hydraulically and not by water-loss, should be used. When using cement-based adhesives on to Gypsum plaster/plasterboard, the substrate should be primed with either Johnson Prime & Seal or Norcros Prime Bond to prevent the formation of ettringite resulting from a reaction between the gypsum and cement.
Once the adhesive has fully dried, the tiles can be grouted in the usual way.
For free technical advice on the Norcros and Johnsons product ranges please call 0870 609 2851 or click here to email. |