I've just done a job where the tiles were supposed to be 445mm square. When I first started fixing them I thought i'd got my 2 and 3 mm spacers mixed together. Alas, that was not the case. When I measured the tiles some were square but a lot of them were 444mm on the two perpendicular sides and 446mm on the other 2. So when the tiles were put on the wall and the 2 446mm edges were in a line, the tiles touched, but along the joint it opened up to 4mm. Explained this to the customer and laid them dry on the floor to show her. I got my thinking head on and rotated the
tile 180 degrees (not back to front) so the joint then evened out. It was a long process and customer complained to the supplier, not my supplier I hasten to add, and they gave her some money back and she paid me extra for making the tiles look good.
Where possible I try to supply the tiles, generally
Spanish or
Italian and don't have any problems.