Decoupling membranes,ditra ??walls,floors??

[Ceramico tiling]

A client wanted a decoupling membrane as she has 15mm stone tiles on the floors and 10mm basalt(I think) on the walls.Do walls move like floors and if so can ditra matting be used on walls?Because I have only ever used it on floors!And if it cant what is the best substrate for walls,,because I was thinking cement board,,and does that act as a decoupling membraine if used on floors??please excuse all the questions but this is confussing stuff!!

All help appreciated

[Phil Hobson]

Hi Russ, I might get shot down in flames for this. Imo decoupling is not really necessary for walls, a good backerboard and tanking plus expansion joints should suffice. Decoupling is more important in floors to allow lateral movement

[Ceramico tiling]

Thanks Phill,do you think I would need expansion joints for a relatively small area such as around a bath.And do you recon cement boards need them??And do they get filled with silicone or do I have to buy something else?

[Phil Hobson]

Sorry Russ,I meant expansion joints in the internal corners.

[grumpygrouter]

I agree with Phil. A good backerboard will be intrinsically inert and resistant to moisture/thermal movement and if you use something like Marmox/Wedi it is also waterproof so only the joints would need sealing.

[Daz]

What is the wall substrate? I think the basalt may be too heavy for anything other than mechanically fixed cement boards / wedi etc..

Cement boards will act as a decoupler on the floor too, provided there is absolutely minimal deflection, however, if it is a screeded floor then a decoupling membrane will be easier to fix as it won't need plugging and screwing down.

[Ceramico tiling]

There is no substrate yet,will prob be cement boards based on these posts.I also had that thin waterproof fabric "knauf" in mind that sticks on the substrate with adhesive.Topps tiles sells it! Is that any good as a decoupling membrane and does it provide a measure of mechanical bonding?

[doug boardley]

if you're sticking cement boards down with addy and screws, I'm not seeing how it can act as a decoupler.