travertine on caber board

[merit]

hi all
whats the way forward in preparing a caber board floor for trav
the floor is going to be a wet room with ufh, someone has installed 12mm ply with a thousand and one screws and finished the shower trays to this height,theres no deflection .
if the shower trays need to be lifted to suit additional sub floor preperation thats not my prob
do i
install cI plus as tanking and de coupling over 12mm ply ,then ufh slc as normal
or do i need to incorperate insulation boards as well or would this be a customer preference
or do i
glue and screw hardi 250 over existing 12mm ply,then cIplus,then ufh then slc
im getting a bit paranoid getting this right as theres a fair bit of work to come off it
thanks for your time

[Gall.B]

The ply should be 18mm or at the very least 15mm, expansion gaps between sheets and a perimeter gap also boards should be primed front back & sides

Is the floor deflection free?

would prefer to use insulation boards glued & screwed if you can get over your height issue.

If using a decoupler I would lay UFH matt, slc then decoupler.

[merit]

thanks for ypur reply ,didnt know if i had to use insulation boards because of timber floor ,is thear a certain wattage of mat ect, height wont be a problem for me ,maybe for others as they are the culprits having already screwed 12mm ply down.