Schluter Ditra - filling square "dovetail" cavities

[Qwerty]

Morning all!

Had one of those middle of the night brainwaves last night that has got me thinking. When installing Ditra I usually back fill the square dovetail cavities with adhesive as I am laying the tiles. I have tried the technique of some by skimming the whole area beforehand, letting this set and then tiling.

I got thinking about this and wondered about the use of a flexible SLC such as Mapei Ultraplan renovation screed in place of adhesive (purely in the cavities)?

The instant issue I can see with this is that there will be a natural weakness joint in materials between the SLC and adhesive bed which could debond under stress, but then again some fixers that backfill first then go on to work on that area for a few days which surely would weaken the bond between the adhesive layers much the same as if using SLC?

Thoughts anyone, and what techniques do you use?

Geoff

 

[Colour Republic]

Never liked the idea, I always back fill as I go as I prefer the adhesive bed to be as one any other way and as you say you are creating another layer that could potentially fail. Only in extreme cases I'm sure but sits better in my head. TBH I don't think you save much time backfilling in one go anyway.

 

[John Benton]

I always fill as I'm tiling so there is only 1 'layer' of adhesive, a continuous bond if you like.

Not sure if that's the right or wrong way to go about it, but that's the way I do it, and to my knowledge I've not ha d a fail yet!

 

[AliGage]

Same as. Back fill, trowel on, back skim and fix.

 

[Qwerty]

Seems so far those who have replied use the same technique as me. Anybody use the cover it all first technique?

 

[John Benton]

Seems so far those who have replied use the same technique as me. Anybody use the cover it all first technique?

I think I've seen jonnyc on his jobs spreading first and then tiling after its dry

 

[Qwerty]

Yes you are right John

 

[Ian]

I think protilers Lee, quite often SLC's over the mat before tiling. I do as many of the others do and do it all in one go with adhesive.

 

[andy8758]

Although like most here I fill the dovetails as I tile, the devil in me thinks that if you fill them first and tile later (using the same adhesive) it is a bit if a myth about a "continuous bond" being better. But I cannot help feeling that filling the voids first is actually slower than filling as you tile.