No more ply (NMP) or Hardiebacker over wet UFH

[Rosewood]

Hi,
I am replacing a tiled floor and will need to overlay with 6mm backer board. This is on top of 15mm ply over wet UFH in dry screed.

I need a backer board with the highest k-value (lowest R-value). So far from the data sheet 6mm hardiebacker has a k-value of 0.19W/mK. Does anyone know what the equivalent is for 6mm No More Ply?

Thanks!

 

[Old Mod]

@HardieBacker can you help please Luke?

 

[Old Mod]

Why are you over boarding a heated screed with ply and a board, may I ask?

 

[Rosewood]

Thats a good question! See this post from some time back that explains the problem.
https://www.tilersforums.com/threads/relaying-lifted-tiles-on-suspended-floor-water-ufh.84468/

 

[Old Mod]

Ok understand now, thank you.
Unfortunately problems like these are almost always budget driven repairs, which is completely understandable, as there are better ways of dealing with the issue.
If you really want to resolve this on a permanent level and you can allow for it in your budget, rip it all back to joist and re cover with either 22mm no more ply, or Gyprocs GIFA board.
Both are inert materials and are not effected by either atmospheric conditions or moisture.
Not the cheapest solution I grant you, both these products are both structural and are ready to tile, as is.
However follow all instructions to the letter before Tiling, there are different preparations before Tiling with either, ignore them and you’ll be back to square one. But a brilliant solution.

 

[Rosewood]

Thanks 3_fall. Yes i can see that this would be the definitive solution. We have a fitted kitchen that would be all but impossible to unfit, and then refit. So we'd need a new kitchen too if we ripped up the whole floor. Hence this compromise.

Incidentally i think i can answer my own question. I found the technical spec for no more ply - the thermal conductivity is 0.41 W/mK. So its twice as conductive as Hardiebacker - which is good for my purposes!

 

[Old Mod]

Yes i can see that this would be the definitive solution. We have a fitted kitchen that would be all but impossible to unfit, and then refit. So we'd need a new kitchen too if we ripped up the whole floor

The kitchen could remain in place as a rule, but anyway, glad you resolved your query, good luck.