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Why Do Tiles Bend Near the Center?

The geometric characteristics of tiles, especially potential bends, affect the quality of porcelain stoneware laying, and the final aesthetic results. In this article we will discuss this aspect in detail.

Due to the increasing popularity of large size rectangular porcelain tiles, we often have to answer questions like: “Why does the tile bend near the center?” or “Why is the tile crooked?”. We specifically wrote this article to explain why and how this happens.

The nature of the bend is directly related to the technology involved in manufacturing porcelain stoneware. Porcelain stoneware is a natural product, only made using natural components such as kaolin clay, kaolin, sand, feldspar, and synthetic pigments. The manufacturing method involves the processing of raw materials under extreme conditions, such as high force pressing and extremely high firing temperatures. This might cause residual stress to build up inside the tile, resulting in geometric deformations. This is less evident in square tiles, but much more in rectangular formats (30×60 and more).


The curvature of a tile is the offset at the center of the plain surface. Each tile undergoes four measurements based on which “convexity” or “concavity” is determined.


According to our technical manufacturing standards, the maximum deviation should not exceed 0.5% of the diagonal size of the tile. This means that, as the tile size increases, the value of the maximum allowable curvature increases as well.



In case you have any doubts about the curvature, we have prepared a guide on how to correctly measure tiles on your own. It is very important to carry out measurements correctly, otherwise, you may get inaccurate results.


  1. Lay the tile on a flat, hard surface.
  2. Measure the gap in the middle of the tile between the edges of the mounting sides and the supporting surface. This can only be done using a feeler gauge.
  3. It is not correct to measure one tile by comparing it to another tile, since the tolerance of one tile would be summed to the tolerance of another.


If you still have doubts, it is necessary to stop laying the tiles and send several samples to the factory laboratory for examination. The laboratory will test the samples with special equipment that provides accurate results.


It is very important to note that the laying of large rectangular porcelain tiles requires special training for the tile layer. We recommend using a tile leveling and alignment system, which will correct any possible deviations and reduce the laying time, as well as achieve excellent aesthetic results.


If you are renovating, you may also be interested in our article “Renovating your house: how to choose a tile layer.” In that article we discuss what to look for when choosing a specialist in order to avoid unpleasant surprises.