Taken from  The Tile Association

The maximum weight of tiling which can be supported by a dry, well-adhered plaster background is 20kg/m². This is equivalent to ceramic tiles with a maximum thickness of 8mm plus tile adhesive or natural stone tiles with a maximum thickness of 7mm plus tile adhesive

The weight of tiling to a plasterboard background direct (without plaster skim) should not exceed 32kg/m². This is equivalent to a ceramic tile and adhesive with a maximum thickness of 12.

Porcelain tilesare ceramic tiles with a water absorption rate of less than 0.5 percent that are used to cover floors and walls. They can either be unglazed or glazed.

Large-scale production of porcelain tile is undertaken in many countries, with the major producers being China, Italy, Spain and Turkey. There are also countries undertaking small-scale production, such as Australia and strong growth in Brazil.

The hardness of the tile can be rated from zero to five according to ISO 10545-7 (also, ASTM C1027) test for surface abrasion resistance of glazed tile, and this can be used to determine suitability for various end use conditions.