alright mate, how do they do it, well it don't take a rocket scientist to work this out

or does it

. This is what they would do. They would work out how much movement is in the floor and how much it will move over time. This is done with a gauge to test for flex on wood and they drill holes in concrete. If there is a lot of movement they sometimes install whats called a floating floor. Then its all down to the tile size. The architec would work all this out and thats what there paid for. I could if you all wanted to get the formula on how its done, guy next door does this for his job.