Nick Bratt, National Technical Sales Manager at tile adhesive manufacturer Palace Chemicals considers some pointers which will help specifiers avoid problems. More detail on these and other issues is contained in the company’s RIBA-approved CPD entitled: Successful specification of wall & floor tiling and how to avoid common failures (palacechemicals.co.uk/technical-services).
While suitability of substrate is critical to ensuring the success of a tiling project, as discussed in our previous column in this publication, another aspect highlighted in the CPD presentation is the specification of the right type of tile adhesive for the project.
Cement-based adhesives are commonly specified for tiling and offer high bond strength for a variety of substrates. However in line with environmental targets set out by the Government and by industry, specifiers should look to choose more environmentally friendly construction products which align with carbon reduction goals.
For example lightweight, high yield adhesives containing recycled low density blown glass are now available, which have a reduced environmental impact and additionally offer up to a 50% weight reduction compared to conventional cement-based adhesives. These adhesives are suitable for fixing all tile types, including large format and natural stone.
Correct application methods
Another factor is the use of the correct application methods for the adhesive, in accordance with the requirements of BS 5385-1, the Code of Practice for Ceramic and Natural Stone Wall and Floor Tiling.
The first approved method is the notched trowelling method. This involves applying the adhesive to the substrate using a trowel as a floated coat, which provides a sufficiently deep and level base coat of adhesive applied to a wall or floor to create a flat and stable substrate for the installation of tiles. Applying the adhesive on to the substrate surface and combing through with a notched trowel creates a series of ribs into which dry tiles should be pressed with a twisting or sliding action to compress the ribs and achieve as much of a solid contact between the two surfaces as possible.
The alternative buttering method is suitable for awkward tiling positions, such as around openings and restricted areas where a notched trowel cannot be used. When using this method, spread the adhesive evenly over the entire back of each dry tile with a trowel. The bed thickness should be slightly greater than the final thickness required to allow for proper adjustment when pressing or tapping each tile into position.
Finally the notched trowelling and buttering method should be used for fixing large tiles and tiles with ribbed, deep keyed or heavy buttoned back profiles. A thin coating of adhesive buttered over the backs of the tiles should fill the deep keys before placing the tiles into position on a combed adhesive bed. There should be no significant increase in the bed thickness.