Wet UFH Limestone DITRA?

[sdw45]

I am a customer not a tiler!

My architect wants to lay limestone tiles directly on to the screed which is a sand and cement mix with the UFH pipes in it. This is laid on a solid concrete base. The screed has SBR and some fibres in it. My worry is that the limestone tiles with all their natural flaws will crack as the heating causes expansions/contractions.

His concern is that the floor will not be as heat efficient and there is a lot of glass potentially creating a lot of heat loss. He wants me to sign an agreement that some tiles may crack and still not use the DITRA.

Does a Ditra laid floor take ages to heat up? How likely are my tiles to crack if I go along with his Plan?
The floor is about 9mx 7m.

Thanks

 

[White Room]

Ditra all the time for limestone with ufh, he should know better.

 

[sdw45]

Ditra all the time for limestone with ufh, he should know better.

Thank you - that's my feeling especially as I am sceptical about how dry the screed will be by the time he aim's to lay the tiles.. I assume that we need to get the heating ramped up slowly too..

 

[White Room]

How long has the screed been down....

 

[Alan.P]

With all due respect, your architect is a muppet, listen to whitebeam's advice, lot's of questions to be answered before a mat or tile are laid, for the tiles and your sake

Welcome to TFUK by the way

 

[Old Mod]

As above ⬆️⬆️⬆️⬆️

 

[sdw45]

Its been down a week - its 55mm and the UFH pipes are in it. I assume it should be another 5 or so weeks to be fully dry then put the uf heating on...
Alan - thanks for the welcome.. I am desperately trying to educate myself so I can make the right call! I am assuming that the Ditra mat will allow some leeway with moisture issues.
Thanks 3-fall

 

[Old Mod]

One of the primary functions of Ditra is that of a vapour barrier, it's used to fast track tiling all the time.
It must be completely sealed tho using Kerdi-Keba and Kerdi Coll.
(A tape and adhesive)

 

[sdw45]

Thanks guys that sounds good advice - how much do you think my underfloor heating will be affected in output - will it take along time to heat up, or is it down to the Ditra being fitted well and all the cavities being filled so the air gaps are minimised? I feel slightly educated about it now!

 

[lizzardtong]

Im not 100% sure but 55mm for sand and cement is bit thin. @Ajax123 would be able to confirm that. Also 55mm should dry in about 60 days. And i would go for decoupling membrane 100%