Decoupling or not

[Perfect Tiling]

Good morning. I am doing a job next week that I need a bit of advice on as I've never come across it before. Customer has a floor with piped water ufh covered with 30mm of plywood and tiles...as expected the floor hardly heats as ply inulates the ufh. The ply is coming up to be replaced with 22mm hardifloor boards. Tiles are possibly travertine. I usually use a decoupling mat under stone especially with ufh (usually within a screed) but hardiebacker say its not necessary and BAL aren't sure. Anyone come across this before. On similar note...if putting down stone on 10mm insulation boards with electric ufh would you use a decoupling mat...even if floors only around 6 sq mtrs. Ta.

 

[Ajax123]

Re: Decoupling or nor

Not sure there is a standard that covers this make up but I would erring on the side of caution given there is UFH and would be using a decoupling system with stone.

 

[IHB]

Re: Decoupling or nor

The ufh is under the hardie flooring?

 

[Diggy]

Re: Decoupling or nor

Large bargepole imho.

 

[widler]

Decoupling or nor

I've used hardie OVER UFH before now, with porcelain tiles though,no ditra,and yes the heat comes through no probs.
it's a cement board and will heat up and stay warm,a lot like a sand cement screed

 

[cam_low]

as above !

 

[nybor62]

imo for a 6m2 floor i woiuld'nt use ditra . . just my take on it

 

[Time's Ran Out]

Always use decoupling under stone and especially with UFH.

 

[widler]

Why would you use ditra if there was no underfloor heating john ?
Surely in all your considerable years you have laid stone with no ditra or such like?
What about a outside patio or driveway,laid on a slab ,open to much more temperature difference than interior and I've never seen ditra or wot else .

Disclaimer- in no way is this a bitchy comment to anyone,I AM ASKING A QUESTION

 

[Perfect Tiling]

Thanks for the replies. Its not normal hardiebacker but hardie floor which is designed to allow good thermal dissipation from wet ufh with no lateral movement...so they say. Customer has now got tiles and they are 333 x 333 porcelain rather than travertine. Still querying the decoupling belt and braces approach...I prefer to do jobs just the once!!!!

 

[Ajax123]

Thanks for the replies. Its not normal hardiebacker but hardie floor which is designed to allow good thermal dissipation from wet ufh with no lateral movement...so they say. Customer has now got tiles and they are 333 x 333 porcelain rather than travertine. Still querying the decoupling belt and braces approach...I prefer to do jobs just the once!!!!

From a purely standards point of view uncoupling is only required for natural stone on heated screed. It can of course be useful on screeds which have become unsound e.g. Cracked sand cement etc.... Porcelain would not normally require uncoupling.

The level of thermal dissipation... Or diffusivity to use the tech term... Depends on a number of factors including primarily flow temperatures and intimacy of contact with the final surface.

 

[Perfect Tiling]

Thanks Ajax. Thats what I thought...good to get second opinion. Customer will be happy as less money and time on the job.