Hi new here so hi to you all.

We do work for a small but luxury hotel chain. Three years ago a builder completed a loft conversion on one of the hotels, within this loft conversion thre batherooms where installed. All the bathroom floors (and walls) were fitted out with travertine 460 x 460 tiles. Since then to now all the floors are cracking and tiles becoming loose. When you bounce on the floor you can feel it move. Whilst there last week it was discovered that the tiles where fitted directly to the chipboard flooring.

Sorry about the length of background.!

We have been asked (as all the floors our company have laid within the hotel have not cracked) to give a quotation to re-tile the floors. My first thought was tiles up (plus possibly the chipboard) re-floor if required then 18mm marine ply screwed every 150mm . Then the flexible adhesive/grout as normal.

The only problem is the finish hieght would not help walkin from the bedroom into the en-suite with out a 20mm high trip hasard. The pan (which has aconceled cisterns) would have to be raised as would the radiators which are floor mounted.

Is ther another method such as this decoupling membrane PCI Pecilastic®

Your help would be very much appricated. The tiler i allways use is on holiday for two weeks and the hoteler would like this costing back ASAP

Sorry but a decoupling membrane will not help, chipboard is not a substrate to tile directly on to. I would go for the rip out the chipboard, and replace with 18mm ply ( good quality). Or if you can add extra noggins, to brace the floor, screw the chipboard down, to eliminate any deflection, then glue and screw a tile backer board on top.

The floor must be bounce free, for the backer board to work. Decoupling membranes do nothing to prevent deflection, just lateral movement. Imo

I'm with Phil here, even thicker ply if you have the height..

Thanks for the advice.

With regard to rip the chipboard out and replace with 18mm ply. Are you suggesting to just fit 18 or 22mm ply direct to the joists or lay new flooring then ply. I have allways laid the ply over a flooring, never direct to joists.

If this is acceptable it would help with the height issue at doors and radiators etc. Although I am sure the floor would still have a "bounce" in it like it has at the moment !

check the size/depth of the joists when you take up the chipboard and check that they have been fixed securely.
loft conversions usually have suspended floors. steel rsj's with the new joists fitted across them. i am pretty sure that will be stable and deflection free but, double check and use noggins at 300mm centres to make them rigid as possible.

i reckon its the chipboard as the lads above said.. sort/replace that and as dave mentioned go for as thick as poss!!!
loft conversions are one of the hottest parts of a building, so there will be lots of expansion and contraction through out the year so its worthing installing a decoupling membrane on to the newly laid ply too imho..

best of luck..