Tiling onto P5 laid on foam

[everonward]

Hi,
I've just removed the tiled floor in our utility room to find the tiles were laid directly onto Caberfloor which is sitting on 45mm thick polystyrene foam on a concrete base. The floor was laid about 25 years ago and was in okay condition other than were a large chest freezer had been.
I've read mixed reviews about tiling onto Caberfloor and so planned to lay a 3mm uncoupler first.
Would welcome any comments and advice from experienced tilers.

 

[JaimieH]

What you currently have is a floating floor and this is the problem. Not many tilers would recommend tiling onto these. An uncoupling membrane won't really do anything to prevent the flexing of the floor when weight is applied to it. I'm guessing that your old tiles or the grout had cracked under the heavy freezer and this would be the reason. Your options are to replace the tiles with either a laminate, vinyl flooring etc or if you really want to tile, remove the everything back to concrete and fix insulated construction boards to it. Marmox boards are an excellent product and vary in thickness up to about 60mm.