preparation for bathroom floors with wet UFH

[andyq]

3 bathroom floors, all with wet UFH, currently have movement in them. Two of them have walk-in shower areas, grout has broken in many places, tiles have lost alignment, tiles move and some are so loose it wouldn't take much effort to get them up.
After the existing tiles are taken up what is the best way to prep the floors to avoid this happening again?
are we talking 22mm or 25mm marine ply on top of the wet UFH, then Ditra matting or some other decoupling membrane
before I fix in flexible addi?
Are there any grouts that are more flexible than others?

The sub floor under the UFH is timber

your advice is appreciated

andy

 

[andyq]

Update,l chipboard was laid over the wet UFH, then 9mm ply screwed into the chipboard, then tiled!
Don't know if the ply was primed beforehand!

A nice fella works for CTD suggested I get in touch with the manufacture of the UFH system, see if they have a tech guide for tiling

Is it a case of rip one floor up and have a look at whats n take it from there?

:huh2:

 

[White Room]

If the other floors are falling apart then they could follow suit....

 

[andyq]

Oh yeah, i'd put a lot of money on it, if I had it! its a dead cert

What would you do whitbeam? rip one up back to the wt UFH pipes and then what? how would you prep it? should I contact the manufactures and see what they say?

 

[Ajax123]

What are the UFH pipes running in??

 

[andyq]

don't know, what different types are there?