Using large format tile has many advantages. Among the most common advantages are easier maintenance and room size perception. Generally speaking, it is far easier to clean the face of a tile than it is to clean the grout and large tile tends to make the room in which it is installed appear larger. The use of large format patterns also creates dynamic looks; dramatically increasing the visual impact of a space.
This trend toward large format tile has presented new and challenging elements requiring additional skills and preparation techniques for the tiling installation professional. For example, the handling of contemporary, very large format tiles borrow techniques from the glass industry utilizing high vacuum suction handles to move and place tiles.
The crucial element to successfully installing large format tiles lies in the preparation of the substrate and using proper installation materials. Whether floor or walls are to receive tile, the flatness and suitability are paramount to prevent lippage. The substrate receiving large format tiles should be prepared to a floor flatness (FF) of >50. All properly prepared substrates should have no more than a 1/8” (3 mm) in variance in 10′ (3.05 m), with no more than 1/16” (1.59 mm) variation in 24′ (7.32 m).
The level of flatness dictated by the BS Standards for large format installations is “local variations in level for a nominally flat floor should be such that, when checked with a 2 mtr straight-edge, any gap under the straightedge between points of contact does not exceed 3 mm.” Not ensuring a flat substrate may create a condition where one edge of the tile is higher than the adjacent tile creating an uneven and unsightly appearance. This condition is called lippage. To achieve the acceptable substrate flatness on floors, it is recommended to use a cement based, smoothing and leveling compound to ensure the proper level required over a large area.
Selection of adhesive
Choosing the right adhesive is important in ensuring that a tiled surface remains intact over the years. In order to choose the most appropriate adhesive, it is important to determine which type of tiles are to be installed, the substrate on which they are to be installed, etc. For large formats it is preferable to use deformable adhesives from class S1 or S2 according to EN 12004 (depending on the expected deformation of the substrate). The adhesive should have the necessary extended open time required for double-buttering technique (i.e., to apply the adhesive on both the back of the tile and on the substrate the tile is to be installed on)
Before applying the adhesive, make sure the back of the tile is clean and there is no dust or impurities present. If required, clean the back of the tile with a damp sponge.
The adhesive is applied over the substrate and combed using a notched trowel. After that, a thin layer of adhesive is spread over the back of the tile with the trowel’s flat side. By using this method, full coverage of the tile with adhesive is ensured.
When the tile is applied to the receiving surface it should have sufficient pressure to expel all the air between the tile and surface. This can be done by deforming the ribs on the surface into the back buttered tile by lightly tamping the surface of the tile with a rubber grout float to ensure good contact or by marrying the ribs on the tile and substrate so that all voids are closed when the tile is pressed and bedded into place.
With large format tiles, the joint width should also be considered as the goal is to have as few joints as possible. In any case, the minimum recommended width between each tile is 2 mm and the width increases according to the area of use and the stresses expected when in service. The grout lines may be filled with a cementitious grout or with an epoxy grout.
It is important to stress that perimeter and field movement joints are required within tile installations. Expansion, construction and contraction joints should be carried through the tile without exception.
Where the tiles have a mesh backing, adhered with a polyester resin which covers the fiberglass mesh, an epoxy-based adhesive such should be used.
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