Floor prep question

[Paul R Cox]

Hi everyone,
I'm pricing a job to tile a bathroom floor with UFH. It's a suspended floor that has been over-boarded with ply and has a thick, hard shiny vinyl on top.
Everything is well fix down and I'd rather not remove it all if possible as it goes under furniture that they don't want to remove. So I'm wondering whether I could glue and screw wedi board over this and if so what people's thoughts were on what adhesive to use? Maybe sticks like sh*t?

 

[Steve the tiler]

A flexible fast set by Webber will do the job

 

[Ajax123]

the screws hold it down so your wedi board should be mechanically fixed with screws and washers ideally into the structural subfloor i.e. the joists, and not just the floor boards. The tile adhesive helps keep it stuck but is primarily there to fill any voids underneath to prevent flexing. One important thing on a floor like this is that there needs to be no flexing in the joists as that will pop/crack your tiles