De-Coupling membrane would you insist

[Ajax123]

Ditra would have kept some moisture there.

It would also have acted as a vapour stbilisation layer allowing the screed to continue drying allbeit very slowly. The moisture would not have been disruptive to the tiles cos they would be separate. As it happens in this case I don't know if the screed was still damp or not.

 

[LM Ceramics]

me personally depends on the tile being fixed if it is ceramics i would use a flexible adhesive grout etc but id place an expansion joint round the perimetre of the room

if using natural stone trav or limestone i would insist on using an un coupling membrane