Floor preparation for between the joist wet underfloor heating

[DMHunter]

Hello,
I have fitted John Guest Speedfit "between the joist wet underfloor heating" and want to lay 40x40 travertine tiles on the floor. Should I use 22mm water resistant chipboard as suggested by John Guest for a generic tile (not specifically travertine and I suspect this is driven from a thermal perspective rather than for rigidity) or 18mm WBP ply as I have done before with (non UFH) travertine floor. I am a bit concerned about how much heat the floor with give off, i.e. will it come through the chip or ply. As far as I can see from googling, the thermal properties of chipboard and ply are the same 0.13 W/(m2 K/m), so I am inclined to go with ply.

Thanks for any advice

[nybor62]

ive just looked at the web site, the floor coverings they recomend are knauff brio boards or ply, deffo not the chip board

[timeless john]

Whatever is your final choice I'd suggest you use a uncoupling membrane such as Ditra before fixing your travertine.

[JLM Tiling]

use ply and a decoupling membrane. Plus don't forget to prime underside of ply before fixing and leave a 1mm expansion gap

[Rich]

You dont want to be bonding to chipboard, it is horrid horrid horrid stuff! Ply is better but still not perfect to bond to and still needs to be fitted correctly.