Large Rectified Tile Installation Problems
With the introduction of large dimensioned rectified tile (24 inch x 24 inch) the quality of the tile has become more an issue. The installation of a mis-formed large rectified tile can produce trip hazards. Lippage, the protrusion of one edge above another, has always been a concern in the industry but now that tiles have gotten larger, lippage has become an increasing problem.
Occasionally, tiles are imported with a high percent of warpage and should not be considered commercially viable for floor applications. In these rare cases, the tiles should only be considered for installations where there is not foot traffic.
It is also important that the project designer is aware of what setting patterns to avoid. If testing show any warpage, then installing a brick pattern (especially with a large format rectangular tile) should not be done. If the designer/customer chooses to install using this pattern, then the tile must be completely flat, or it cannot be installed without lippage.
Fortunately, warpage is rarely a problem with most tiles. Overwhelmingly, the majority of lippage is caused by an uneven substrate or improper application of setting material while attempting to compensate for irregularities in the sub floor. Generally, it is well worth the time and money to flatten the floor first. Self-leveling cements are excellent for this purpose, although a skilled installer can also level a floor with thin set and careful use of his trowel (although, depending on the extent of the problem, it may take more than one pass). Not only does a flat substrate help avoid lippage, it usually makes it easier and faster to install the tile.