Tiling Advice Wanted - Over Wet UFH

[swampie]

Hi All,

I have some 600x600mm Marble tiles to lay over an underfloor heating system and would like advice on adhesives and fitting please?

Floor Construction​

• 
  [*=2]220mm Suspended timber floor joists - ***New build and pretty level***
  [*=2]Batons supporting 100mm Rigid Insulation Board between joists (set 25mm below joist top)
  [*=2]16mm UFH Pipe clipped to insulation Boards
  [*=2]Dry Biscuit Mix Screed, around pipework & leveled to joist top
  [*=2]22mm Moisture Resistant Chipboard
  [*=2]9mm Ply Screwed every 150mm
  [*=2]Kitchen Floor

​

So, what is the best method of fixing tiles to the ply to avoid cracking and lifting, I understand a flexible adhesive is needed but after reading some manufacturers fitting instructions, some are only good for tiles up to 100mm, some are super-flex but don't mention UFH applications. It's becoming a minefield of over-information.

Please help, this job means a lot to me.​

 

[Qwerty]

I wouldn't tile that

 

[Andy Allen]

Im out...!!!

 

[Rookery]

You have a combination of a timber floor, UFH, 9mm ply and a soft stone. It's a recipe for disaster which is why the suggestions so far have been to avoid the job.

 

[swampie]

It's going to be pretty tough to avoid, it's my house and it's also my kitchen, it needs tiling really.

Would you all be suggesting it'd be a nightmare job if I'd got hardie board instead of ply?

 

[Ian]

If I were to tile this floor I would be fitting hardiebacker over the chip board, then ditra ontop of that, then tile.

 

[Rookery]

Agreed.

 

[Just Rizzle]

31mm of heat resistant wood
my advice bin the marble tiles the product I would lay would be karndean or amtico

 

[Dave]

This would have been an ideal product if you had researched further >>> http://www.jameshardie.co.uk/hardiefloor

 

[swampie]

Thanks for the tips guys, I wish I had researched more earlier David but I'm now where I am unfortunately but at least I haven't laid them yet.
Yes that structured floor looks just the ticket, wish I'd got that down.

Ray, those are well worthy of further research, thanks for the tips. I'm not sure it'd beat the real thing though, these 600x600's are nice and will last "if laid correct". I'm scared of marking Vinyl.

So if I do tile, is keeping the ply better than removing it, when considering the advice of adding hardie backer and Ditra?

Is ply so bad? My joiner insists its the way to go. For future reference, never ply even without UFH?

ps My tiles are 600x600x15mm. Will the height make any difference to your opinions?