Over the last decade there has been a growth in the use of both electrical and wet system under floor heating and a parallel growth in the use of large format tiles has created a new set of problems for the installer. The first thing to remember is that the rapid expansion and contraction of the subfloor creates a very high level of stress, much higher than an unheated floor. Guidance from the British Standards has not kept up with the needs of the installer, The Tile Association however have been more forthcoming in recognizing that more guidance is needed. Essentially, guidelines are the same as a standard installation but with reduced field sizes. The TTA suggests that no field of tiling should exceed 40 squared meters with no one side exceeding 8 meters in length before a stress-relieving joint is installed.
Due to the high degree of stress within these installations, we suggest that there should be a distance of no more than 5 meters between stress relieving joints. It is a big mistake to ignore these sensible rules because subsequent problems are very difficult to correct.