Tiling onto Ply, can it be a success?

[Boggs]

I have seen this twice before, there was a poly layer between joists and ply for moisture.
But maybe that was one because the finished floor was timber, can’t remember but worth checking.

Why not stick and screw 6mm Hardie backer to the floor before tiling instead of the Ditra.

 

[Flintstone]

Then turn the heating on in August just in time for it to be warmed up for around bonfire night !

 

[J Sid]

my main concern is is the floor under the ply completely dry!
this is what will happen if you trap moisture under Ditra onto ply.

 

[J Sid]

and that was just a hole in the sealed bag of clay infill for round the ufh pipes.

 

[AD1]

I have read a lot of conflicting opinions on using S2 over Ditra. I decided to go with Ultimate S2 as I read US and UK specs are different and S2 is suitable according to UK spec.

I did think the screed was anhydrite but from a quick Google search it seems it's not. It is a dry mix with fibre glass reinforcement and was shovelled in and packed in between joists and compressed.

The heating works perfectly, UFH manifold flow temp set at 50 degrees, the house is warm and our living has laminate which is warm to touch. Takes around 1 hour to heat up to temperature.

I also chose a 3mm V notch as this is what is specified by Ardex, should I go larger notch? I may need another tub if so.

Thanks for the replies.

 

[Old Mod]

I have read a lot of conflicting opinions on using S2 over Ditra. I decided to go with Ultimate S2 as I read US and UK specs are different and S2 is suitable according to UK spec.

I’m afraid you are mistaken. An S2 adhesive is NOT suitable if you follow schluters guideline.
They WILL NOT honour any guarantees.

 

[charliesw4]

I’d personally ditch the ditra and overboard with 6mm Hardie. S1 adhesive is fine.

 

[Old Mod]

... and to be honest, you’ll struggle to use Ultimate and not throw most away.
And to use that over top of Ditra, you’ll be lucky to return 3m2 a bag.
You’re looking at approx 15 bags to be sure you have enough.

 

[Boggs]

What’s the reason for S2 being unsuitable?

 

[Old Mod]

What’s the reason for S2 being unsuitable?

In a nutshell it’s too deformable.