HELP! Electric Underfloor Heating and timber suspended floor

[QuestionsQuestions]

Hi. I am looking for some advice.
Currently got a new extension with a suspended timber floor insulated between rafters with polystyrene and boarded and sealed on top. I want to lay electric underfloor heating someone suggested using hardie backer cement board (6mm) on top of board screwed down to limit movement when tiles are laid..however, I wanted something that would limit movement AND add insulation will this limit movement as well as adding insulation?
http://www.theunderfloorheatingstor...ic/prowarm-trade-backer-pro-tile-backer-board

We have limited depth owing to low threshold door so maximum is about 26-28mm and tiles are 8-10mm deep.
PLease anyone got any experience

With Thanks

 

[vinn]

I'm not sure what movement you wish to limit.
If you have boarded the floor with something suitable then you could tile directly over ply for instance.
Using thick bed trowelling the UFH cable can be laid in the thick bed adhesive directly under the tile.

 

[Doggit]

I don't have any experience of them, but they look like XPS insulation boards with a cement face, so should be okay. What is the floor boarded with at the minute.

The boards are 6mm, and the tiles 8mm, and you'll need to allow 3 to 4mm for the adhesive bed, so what's the thickness of the heating mat, and how thick is the channel for the thermostat. You'll want a flexible adhesive for this job, and a good trick is to turn the heating mat over so that you don't nick the wires as you lay the adhesive, otherwise you'll need to apply the adhesive to the back of the tiles. Some people recommend a flexible self levelling compound on top of the mat, but I'm not sure if you've got the leeway for that.