Does size really matter?

[Fizz_bosh]

Hello again folks,

Thanks for all the useful replies to my question yesterday...
here's today's question.

I have 22mm chipboard, 9mm marine ply & am now considering a tile backer board to give some insulation for my ufh & provide a strong waterproof surface for my limestone tiles. I don't have any room to add this really, because of carpet level outside the bathroom, but if it's really advisable then I will make room, I saw a product by Marmox which is only 4mm thick. I am also considering tanking the ply with Bal WP1 ready for tiling.

Any advice on thickness of tilebacker? Bearing in mind that the bathroom will have light use.

Thanks.

 

[nybor62]

could you not remove the chipboard , and replace with 18 mm wpb ply then over board with min 6mm backer boards , then the ufh cable which will add another 5mm to height coverd with slc compound, you may need to consider a decoupling membrane for your stone aswell

 

[Fizz_bosh]

Hi, thx for your reply.
I don't really want to remove the chipboard, have had all the pumbing sorted & built bath frame all fixed to the ply, Really only considering adding a thin tile backer because I've read alot on here about not tiling directly onto ply
if a 4-6mm tilebacker is worth adding for insulation & waterproofing, I'll go for it. If not, I might just tank the ply.

 

[Fizz_bosh]

Ahh - decoupler membrane = ditra matting?
does that go under or over the ufh?
thanks

 

[nybor62]

under the ditra