Bathroom Floor, Ply and/or Cement boards

[jmc1234]

Hi everyone, I would appreciate a little advice on preparing a bathroom floor for tiling, the area is only 2x2m and feels fairly solid underfoot. I have read lots of good info here but I am a little confused as some threads say you should overboard with a minimum of 18mm ply and then 6mm cement boards, others say the floors can be over boarded using only 6mm thick cement boards with no requirement for the 18mm ply.

Could someone also explain deflection and how to measure it and the minimum requirement before for tiling?

Thanks in advance

 

[Mike]

you should also screw the cement boards down, every 150mm.
the decoupling mat will go on top of the cement boards.
the shower base will be okay on the ply provided the ply is fixed solid and that you don't have any height issues regarding the tiles being close to the top of the tray