Traditional mortar or standard-grade adhesive is not recommended for fixing low-absorbent and non-absorbent tiles because of the less porosities, which can be the cause of dislodged tiles. Specific adhesive with additives providing flexibility and good bonding properties should be used when tiling low-absorbent and non-absorbent tiles.
How to test the tile absorption?
An easy way to test tiles absorption is to drop little amount of water on the tile back.
If water is absorbed quite quickly, the tile is considered to be normal absorbent type.
If water is still on tile back and takes time to be absorbed, the tile is considered to be low-absorbent type.
If water is always on tile back without any absorption, the tile is considered to be non-absorbent type.
Water absorption of large tiles: such as granites and marbles, depends on their sources of production. Special-grade tile adhesive designing for large-size tiles should be used for tiling even they have high water absorption.
Tiles can be differentiated according to their water absorption into 3 types as follow:
Absorbent tile: absorbent value more than 3% e.g. ceramic tile
Low-absorbent tile: absorbent value between 0.5 - 3% e.g. homogeneous tile, granite tile
Non-absorbent tile: absorbent value less than 0.5% e.g. rustic tile, glass mosaics, resin mosaic.