Which way do you do it?

[Rick-o]

Hi all,
Was talking with an adhesive rep yesterday and he was demonstrating some slc.. his demo was over decoupling membrane which raised the question.. Do you level over the decoupling membrane or under it?
If you had under tile heating for example would you put this on the levelled (wood lets say) floor then mat over or would you mat the floor then cable and level?
Rick
By the way he said either is acceptable!!

 

[Tile Shop]

wood substrate - insulation boards - wires - slc - decoupling - adhesive - tiles

an additional Decoupling membrane shouldn't be required as the coated insulation boards have decoupling properties, but also if they are fitted correctly, any movement will be absolutely minimal.

But if you wanted to go belts and braces it would do no harm, but i've always been advised that the decoup always goes over the slc. For instance with ditra, the adhesive doesn't stick to it, but anchors into it so that the matting is free to stretch without transferring the stress. SLC may work the same way but speak to the manufacturer before doing it.

 

[J Sid]

what uncoupling membrane was it and what was the slc ?

 

[Rick-o]

I am with you Paul, I have (at least for the last few years) put the membrane on last. I do tend to use it as I know a couple of tilers that have had floors fail just using 6mm board, which apparently was glued and screwed??
The leveller was ardex (any of them but this was arditex Na) and it was onto ditra matting.

 

[J Sid]

I am with you Paul, I have (at least for the last few years) put the membrane on last. I do tend to use it as I know a couple of tilers that have had floors fail just using 6mm board, which apparently was glued and screwed??
The leveller was ardex (any of them but this was arditex Na) and it was onto ditra matting.

Ditra say no, no, no to levelling on top

 

[hmtiling]

As above. The mechanical bond between adhesive and ditra is lost.

 

[J Sid]

really surprised an Ardex rep would consider doing this with there close relationship with Schluter.

 

[Rick-o]

Yeah I was too Julian as I had seen Schluter recommended ditra being directly under the tile.. He did say Schluter recommend that way due to the ease of getting tiles up but they were happy which ever way it was done.. To me I would go with what schluter say but wondered what other peoples opinions were!

 

[One Day]

As above. The mechanical bond between adhesive and ditra is lost.

No, it weakens a bit. Reliant on the bond between the slc and adhesive.
You can do it that way - at least that what they said last time I was there!

 

[hmtiling]

No, it weakens a bit. Reliant on the bond between the slc and adhesive.
You can do it that way - at least that what they said last time I was there!

No, the mechanical bond between the ADHESIVE and ditra is lost impish if it's been slc'd

 

[J Sid]

Ditra works on the fact that the adhesive or slc if you wish, doesn't bond to the mat but is lock into it.
if you decide to use slc on top to level the floor or cover ufh wires you will exceed the max aloud, (10mm) between tile a membrane.
as most ufh wires required a 10mm slc over the top Ditra would not work.

 

[Flintstone]

Recommended 10mm of slc over ufh wires ? Not sure that's right

 

[Spare Tool]

Recommended 10mm of slc over ufh wires ? Not sure that's right

Not all recommend that, but Webber spec 10mm

 

[Flintstone]

That's probably so you use more of there gear.

 

[Spare Tool]

Ive just been to see a job in a house I did a floor for a month ago, porc planks on ci matt on 10mm Webber slc over ufh with 6mm ins boards underneath the lot, Webber grout cracking around one tile out of 25sqm....there was a hairline crack in base screed at that exact point, whole lot of levels to get through there but its found its way through, newbuild so think its just settlement, gonna regrout it and see what happens..