For high-quality tile laying, the method of applying tile adhesive (masonry mortar) is of great importance. As you know, porcelain stoneware is not afraid of the most severe operating conditions. If it is laid on the base according to all the rules, then a large impact force is required for the tile to lose adhesion to the masonry mortar or a solid base.
This can only be achieved by using the correct technique for applying the adhesive using a notched trowel. But since tiles, along with hardness, are brittle, like glass, the areas under the tiles that are not filled with masonry mortar become potentially weak.If this happens to porcelain stoneware, then a not too strong blow, measured load and other non-fatal reasons can cause it to peel off or become damaged.
Also, you should not lay the tiles without a gap, although this simplifies the work of creating a tile covering. In this case, the most minor circumstances, such as an increase or decrease in temperature, can cause the tiles to break. In such situations, it is also necessary to follow the ANSI (American National Standards Institute) standards, which are recommended by the NTCA (National Tile Contractors Association).
In many cases, when laying tiles, especially large ones, the work technology is violated, which causes breakdowns and expensive repairs. This is also caused by haste in work, since the quality of the work suffers.
One of the major disadvantages of laying tiles is trapping air between the tiles and the adhesive. The areas where air pockets form are weakened as they remain unattached to the substrate.
This defect is often observed when the masonry mortar is spread with a notched trowel in zigzag, circular and other intricate movements.
The tiles above the voids crack over time, and the adhesive composition is destroyed even under normal operating conditions, let alone a point load or a strong impact.
Even in the absence of impact loads and point forces, tiles laid with a violation of the distribution of the masonry mortar can fail even due to minor influences, such as: unevenness of the base, the presence of shrinkage and creep, expansion of the material when heated, alternating freezing and thawing and etc.
The tile is considered securely glued when this is done over its entire area, including the perimeter. What strength can we talk about if it is glued halfway or less. According to ANSI and the TCNA reference book, tiles indoors must be glued to at least 80% of their area and 95% outdoors or in a wet room. This figure for natural stone tiles must be at least 95%, regardless of the location of its installation.
It should also be borne in mind that among large tiles there are often specimens with a protruding center and beveled edges. To hide these defects, you have to increase the volume of the adhesive solution used. If you continue to apply it in a circular motion with a notched trowel, the likelihood of trapping air inside the solution increases even more.
It is very important for high-quality laying of large format tiles that the horizontal flatness of the base is ideal. According to TCNA and ANSI recommendations, the floor flatness error should be within 6.5 mm per 3 meters. If at least one side of the tile is 38 cm, then the conditions for the flatness of the base are even stricter - 3.2 mm by 254 mm and not even more than 1.6 mm by 610 mm.
So, taking into account all the factors, for successful laying of tiles, the masonry mortar must be applied using straight-line movements of a notched trowel.As a result, straight ridges and depressions are formed on the surface of the solution, which are easily crushed when laying the tiles, and air is almost completely removed from them.
Such a linear distribution of the adhesive composition helps to remove air from it and ensure more complete contact with the tile and base, and therefore a stronger connection of all elements of the floor covering.
First, the masonry mortar is applied and spread over the base using the flat side of a spatula. Then an additional amount of solution is applied on top and leveled over the base in straight unidirectional lines, which, among other things, contributes to better distribution of the adhesive composition.
If the tile is rectangular, then the lines drawn with a spatula should be perpendicular to the long side of the tile. This makes it easier for air to escape from under the tiles when laying them.
It is necessary to ensure that air does not remain in the cavities of the mortar and between the tiles. The larger the tile, the deeper the teeth of the spatula should be.
Before laying any tile, including large-format, glass or natural stone, a small amount of mortar is placed on its back side with a trowel and leveled over the entire surface in an even layer with the flat side of the spatula.
Now it is necessary to turn the tile prepared in this way over and carefully lay the entire surface on the prepared layer of masonry mortar and move it several times in one direction and the other with an amplitude of 3.2 to 6.4 mm perpendicular to the ridges of the adhesive mortar lying on the base. Moreover, it is strictly not recommended to move it in the opposite direction and not to twist the tile.
The first glued one, and then periodically, it is necessary to tear off the tile and check the distribution of the mortar on its reverse side. It is normal for the solution to look like pebbled skin on her. There should be no ridges left by the spatula on the masonry mortar where the tiles are torn off. This picture suggests that there is no air under the tile, and the glue is distributed over the entire surface in an even layer.
If you correctly and completely follow all the NTCA recommendations outlined above, then your tiles will lie flat and very firmly on the substrate. Moreover, the larger the spatula you use, the greater the movement of the tiles back and forth when laying them.
