Tiling onto ply over water ufh

[stusgsx]

Hi guys,
Looked at a large job which includes 5 bathrooms which have water ufh which is set in what looks like chipboard channels and then 9mm ply over the top. I have not tiled onto ply for years since moving over to backer and never tiled onto ply which is over ufh.
I can't screw backer over the ply as I'm sure to hit a pipe.
How would you tackle this?

 

[On one]

On a large job with 5 bathrooms is there not an architect to tell you. I thought they knew everything!

 

[On one]

9mm boarding doesn't sound too promising.

 

[stusgsx]

It's a self build and the ufh is a new system apparently.
I will try get a photo tomorrow.
I know 9mm ply is no good normally but it's glued and screwed already :-/

 

[nybor62]

i would'nt tile it , buts that me . there may be problems ahead

 

[On one]

It's a self build and the ufh is a new system apparently.
I will try get a photo tomorrow.
I know 9mm ply is no good normally but it's glued and screwed already :-/

And edges fully supported with noggins?
I walked away from a similar (self renovation) job that was boarded straight onto the joists with 18mm WBP,but with no noggins under the edges. Large format marble to boot as well.

 

[stusgsx]

The floor itself is really solid I'm just worried about going onto ply when it's going to be expanding with best etc. I'm thinking ditra matting at least

Found a section that is visible to show the ufh. You've got 22mm green chipboard, 15mm mdf with pipe inserts sunk in then 9mm ply glued and screwed

 

[widler]

Why can't you screw 6mm backer board on, say no more ply

 

[stusgsx]

Tbh that's a last resort I'm worried it will stop too much heat coming through plus screwing into one of the pipes

 

[m3fitter]

we did a project with this system, wet pipes with metal holders, we adhered 12mm dukka to the system, it was solid, they took up the temp slowly over 2 weeks, and then we decoupled it with ditra, 20mm stone, the jobs been down 2 years, we tiled their bathrooms this year, the floor was perfect.