Tiles are getting bigger and bigger and can range up to 2 metres square however this is a bit too large for the average customers house.
A very common size now is 600mm x 600mm or 600mm x 300mm
A big mistake many people make when tiling with this size tile is in the adhesive selection, popping down to your local DIY store and getting some ready mixed tub adhesive is not the answer when fitting this size of tile.
Ready mixed tub adhesive cures through water loss and this water escapes through the joints of the tile or through the background, the size of large format tiles can stop this from happening.
Tub adhesives can take up to 5 days for the water to escape, again this length of drying time can cause problems and failure in large format tiles.
Porcelain tiles are even worse; they have extremely low porosity, which stops the adhesive loosing water.
The correct answer for fitting large format tiles is by using powdered cements adhesives which are poly modified, they cure much faster than ready mixed dispersion adhesives , cement adhesive dry with a chemical reaction and is therefore a stronger more safer adhesive to use than ready mixed tub adhesive.
When using cement adhesive always make sure the substrate surface is primed with a good acrylic or SBR primer, this can stop any chemical reactions going on between the adhesive and background which can cause tile failure.
Always make sure the substrate surface can hold the weight of the tile you are using, a plaster skim surface will hold 20kg / m2 where as a plaster board surface will hold 32kg / m2.