Prep for ensuite floor

[Retroelec]

Hi.
Need to tile ensuite floor in extension which has currently got new T&G floorboards down.
Am having underfloor heating, one of the Prowire kits from Topps which suggest you put down a thermal backing board (6 mm or 10mm) that they sell.
Could they be fixed straight on the floorboards?
Or would you suggest that I ply over the floorboards then fix these boards to that and if so what size ply should I go for?

Thanks

 

[Mark Frost]

Glue and screw the 10mm insulation board down no need to use ply.. make sure the T&G boards are solid with no deflection. Put your wire on top then Self level over it, encapsulating all the wires.

 

[Simon Dale]

Matting

 

[Dab_18]

Argee with what mark frost says, As I believe topps sell warm up thermal boards (or did when I worked there) assuming the t&g floorboards are solid and well screwed down, using a 10mm thermal board there will be no need for ply,