Cement board vs ply under tiles for wet UFH system

[ollyp3192]

Hi there, we have just installed a Hetta UFH system.. they recommend a 6mm plywood over the top before tiling. I called them and they admitted that ply is a poor conductor.

Does anyone have any experience with cement board (such as Hardie backer or similar) to improve thermal transfer in these cases? Screed not possible.

Many thanks

 

[Kastar UK]

Cement boards work like screed warm up and hold the heat for a while

 

[Dan]

Is it already encased in a flexible screed?

If so go straight over with that flexible adhesive for screed. Don't need another barrier between it. (somebody will need remind me of a name)

The fact the guy said plywood means he doesn't know what he's doing with the tiling part or hasn't updated with the times maybe.

Plywood can't be tiled now at all, and certainly not on top of ufh where it will expand and warp and pop apart in the middle and all sorts.

It's terrible cheap stuff we get now it isn't like the solid stuff it used to be.

 

[ollyp3192]

Thanks all. Can’t use screed over the top of this system. The Hetta instructions say to use 6mm ply as separating layer over the top of the grooved chipboard in which the pipes are running.

Will try and find some 6mm cement board to use instead, any recommendations? Very grateful for all your help.