Best construction/prep method for bathroom floor?

[indus]

Hi

I'm having an ensuite shower room fitted into what used to be a bedroom. At the moment the floor just consists of joists and I intend to have electrical underfloor heating.

In layers starting from the joists up, what should I use?

(Confused about what combination of ply, insulation board and hardie backer to use)

Many thanks for your help

 

[indus]

Hi guys

I would really appreciate some help with this.

Do I need 18mm wbp and some kind of insulated board because of the ufh??

Many thanks