Hi, I have caber flooring in my bathroom (green chipboard t+g) It is screwed to the joists with sheets of 3mm hardboard then fixed on top. This was done about 4 years ago and has been tiled all that time with no problems but I am going to re-tile the bathroom soon and want to know if I should leave the Caber and hardboard alone and just re-tile over it or should I be replacing it all with something else?