Tiling on wet under floor heating

[burncross]

Hi, need a bit of advise for a up coming job.
It is a large kitchen floor, timber floor boards. Plumber has installed warm water under floor heating that works off the boiler. Plastic pipe that fits into a insulation board with a foil top, which is screwed to the floor. My concern is the insulation board is like a polysterene type material.
So my questions are, what is the best material and thickness to overboard this with? 6mm backer board or 12mm ply?
and what adhesive, BAL fastflex?
thanks

 

[m3fitter]

Came across this 6 months ago, looks a right mess, with pipes and aluminium.. create a substrate, we used 12mm dukka panel totally solid bedded onto this, and then we ditra matted it afterwards. the dukka was solid after installation, the ditra just made sure, belt & braces..

 

[burncross]

Did you mechanically fix the dukkaboard with screws, on top of the foil insulation boards, then bed the dittra mat with flexible adhesive?

 

[Chalker]

Have done this using fermacell boards.

but who has specified the job? Surely they should be telling you how to tile onto it?

 

[Chalker]

If tiling, this is the system that should have been used, it's grooved fermacell that you screw down.
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