The purpose of the tile adhesive is to adhere to the substrate and the tile and to ensure the stability of the adhesion in spite of the movement of the building and any movement caused during use.
Conventional cement-based tile adhesives do not adhere to tiles with a very low water absorption rate, glass mosaic and similar tiles with a low to zero water absorption rate. To ensure the correct installation of such tiles, the tile adhesive used must be polymer-enriched to a significant extent.
All tile adhesives sold in the European Union must be tested and labelled in accordance with standard EN 12004. The above mentioned standard covers cement-based tile adhesives (Type C), resin-based (Type R) and dispersion-based (Type D).
Class No. 1 shows that the mixture has at least 0.5 N / mm² adhesion under normal conditions as well as after freezing cycles, heating and aging in water. No. 2 shows an adhesion of at least 1.0 N / mm² under the above conditions. Fast-setting adhesives are marked with the letter F, if the tile adhesive holds the tile without being supported from below, the letter T can be added to this class. Mixes that can be left open for an extended period of time (30 min) are marked with the letter E.
If the tile adhesive can withstand a deformation of up to 2.5 mm, the product is placed in class S1 and can be called flexible. However, if the adhesive can withstand a deformation of 5 mm or more, it belongs in class S2 i.e. a tile adhesive with the highest flexibility.
A product marked with C1 is a normal tile adhesive with no additional properties. With the symbol C2TE S2 we have a cement-based C tile adhesive with improved adhesion 2, that is non-flowing T, with an extended opening time E and the highest flexibility S2.
The tiles must definitely be sorted before you begin tiling, as doing so will ensure a good-looking end result that follows the deformation joints in the substrate. The tile adhesive is not suitable for creating slopes; if necessary, the substrate must be levelled in advance. The required waterproofing must be performed in wet rooms. The tile adhesive is applied in an even layer to the substrate, using a serrated plaster knife, and, if necessary, to the back of the tile. The tile is pressed into the mixture using a rubbing movement, to obtain the largest possible contact area. It is good to use jointing string or crosses to obtain joints of uniform width.
The greater the possible level of deformations of the substrate and the larger the tiles, the thicker the adhesive layer and the higher the flexibility class of the adhesive used for installation should be. Tiles are considered to be large, when one or more sides are longer than 30 cm and no side exceeds 120 cm. The tolerance of the substrate must be a maximum of +/- 2 mm for every two metres. A tile adhesive can be used to compensate for this unevenness. Tiles that are larger than 120 cm in length require a more level substrate than smaller tiles. In that case the surface must be levelled with the fine-grained self-levelling compound mira 6600 cemplan, which can be applied in a layer of 10 to practically zero millimetres.
When using larger tiles, a notched trowel is recommended to apply the adhesive to the tile. The dry layer (skin) that appears on the adhesive, reducing the adhesion, develops at a slower rate when the adhesive is applied with a notched trowel. It is also easier to press large plates into the adhesive in such a way that sufficient tile coverage is achieved.
To achieve the correct layer thickness, the notched trowel must be kept at the correct angle (70 – 80º). The thicker the adhesive layer, the longer the drying time is as well.
The joints between tiles must be filled with a suitable cement-based or epo-based grout. Sanitary silicone sealant mira supersil is used where different materials connect, in corners and other similar joints.