Big Tiles, Big Challenges
Large-format tiles are trending: as a cost-effective alternative to natural stone, XXL porcelain tiles make walls and floors look as if they have been produced in a single casting. Naturally, before we can see just how stunning they are, they first have to be installed. But: large-format tiles mean big challenges – for the tiler and the materials used. Our video shows how a 1.20 m x 2.60 m tile is installed.
When we talk about tiles, what qualifies as ‘large’ in one country may not be considered ‘large’ in another. Tiles measuring 30 x 60 cm are considered large in Europe, but 60 x 60 cm tiles have long been common in other countries – and they can even be much larger: sizes up to 150 x 300 cm may be rare, but they certainly exist. To securely attach these elegant giants to a wall, there are two things experienced tilers need: the right tile adhesive and the right technique.
Large-format tiles create joint-free surfaces that look particularly elegant. But they also pose their own special challenges.
Low porosity:
Large-format tiles are generally porcelain tiles and have a water absorption capacity of less than around 0.5 %. They often have a highly textured back side. This places special demands on the tile adhesive and the installation technique.
Here you can see how low the porosity of a porcelain tile is: the water forms droplets on the back of the tile and is not absorbed. In this case, adhesion can only be achieved with a polymer-modified tile adhesive. As the back side is highly textured, back-buttering is especially necessary, i.e. the adhesive must be applied to the back of the tile as well. Otherwise, the tile might not be wetted completely, and voids may form. Floor tiles with voids underneath are particularly likely to break when placed under load.
Heavy weight:
The larger the tile, the heavier it is. A tile measuring 120 cm x 120 cm can weigh 20 kg and more. Therefore, special tools and a tile adhesive offering good initial adhesion and sag resistance are needed for installation.
Hydraulic suction lifters are handy for lifting and positioning tiles. The job of the adhesive is to immediately create a strong bond between the tile and the substrate, ensuring that the tile does not slip or fall off.
Uneven surfaces:
Walls and floors are never perfectly flat. The same applies to tiles. The substrate and tile may appear perfectly flat, but there will be irregularities at the surface level that the adhesive needs to even out.
The adhesive is therefore applied both to the wall or floor and to the back of the tiles (back-buttering) to ensure reliable wetting and create a strong bond.
Fewer grout joints:
As tile and substrate are made of different materials, they will inevitably experience differential movement, e.g. due to temperature changes. This creates shear forces, which, in the case of small tiles, are partially absorbed by the grout joints. The use of large-format tiles means fewer grout joints. This means that the adhesive must be capable of absorbing the shear forces to prevent the tiles from cracking.
To keep their weight down, large-format tiles are often supplied in a thickness of just 6 mm. This makes them even more susceptible to stress cracking.
As large-format tiles are hard to handle, installing them usually requires more than one tiler and the use of suction lifters. But that’s not all, of course: for a long-lasting result, it is crucial that the tiles be completely wetted. That calls for the right tools and the right technique.
Selecting the right notched trowel:
Large-format tiles are laid in a thin bed of polymer-modified tile adhesive. The thin bed of adhesive is applied with a notched trowel and the tile is pressed on or pushed in gently. The amount of adhesive applied depends on the notches of the trowel.
An 8-mm notched trowel is often chosen for applying the adhesive to walls and floors, with a 6-mm notched trowel being used for back-buttering.
Applying adhesive to both sides:
The tile adhesive must be applied to "both sides": the substrate (wall or floor) and the back of the tile. Back-buttering ensures that the tile is sufficiently wetted and that there are no voids.
As it takes longer to cover a large area with twice as much adhesive, it is helpful to use a tile adhesive that has a long open time.
Tiles and tiling techniques place high demands on the tile adhesive. Experienced tilers recommend using adhesives with an EN C2TES1 or C2TES2 rating. These adhesives are characterized by high tensile adhesion strength, flexibility, slip resistance and an extended open time.
High Tensile Adhesion Strength
Large-format tiles are heavy. For a really secure bond, they require a Class C2 adhesive.
Flexibility
Highly flexible tile adhesives can compensate for movements of the substrate and can absorb shear forces. Highly flexible tile adhesives are rated “S1” and “S2” in the European standard.
Long Open Time
An adhesive applied to large areas of substrate and the backs of the tiles should have an open time of at least 30 minutes. Adhesives with an extended open time are rated “E” in the European standard.
Good Initial Adhesion and Sag Resistance
As soon as the tiles are pressed against the wall, they should adhere strongly without slipping. Adhesives exhibiting this property are rated “T” for thixotropic.
What Happens in Practice
We tried it out. Experienced tilers were tasked with installing a large-format tile on a wall in our Technical Center in Burghausen. Here is the result:
What the Technical Tests Reveal
Once the tile had been installed, we tested the tensile adhesion strength. The results show good wetting and strong bonding of the tile.
Would You Like to Know More about Our Tile Adhesive Solutions?
With our wide range of products, you can formulate tile adhesives for a variety of tile formats and applications. Visit our product section for more on this.
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