Maybe I should of not mentioned all the bits except for just advice on the best https://www.tilersforums.com/forums/tile-adhesive/ to use on a sand and cement screed.
Yeah, then you might have got the wrong advise given to you. Got to say, you seem to have a bit of an attitude for not getting a straight answer. Unless i'm reading it wrong. Understand that
tile is not as straightforward as many think and its the first visual part of the installation you notice when the floor beneath goes belly-up and its not been prepped correctly. Any bag that says tile
https://www.tilersforums.com/forums/tile-adhesive/ will stick to sand and cement. Doesn't mean its right for the overall installation though.
So if you want an honest answer, heres one for you...... and you might not like it. You need to leave your floor 100 days to naturally cure. 1 day per mm for the first 50mm the 2 days per mm for the other 25mm. You also need to commission your underfloor heating for the screed to adjust to the thermal expansion.
After 100 days, the heating has been commissioned and you have checked the relative humidity of the floor and if no cracks appear in the screed, prime it with a suitable acryllic or SBR primer, level it with a flexible levelling compound if required and tile it with an S1 flexi
https://www.tilersforums.com/forums/tile-adhesive/. If cracks do appear, repair them with a suitable repair morter, and tile as above but this time, incorporate an anti-fracture matting. Cracks or no cracks, you will also need to split the room into two equal size bays and stick an expansion strip down the middle. This is because its a heated area over 40 sqm.
If you're impatient and don't want to wait (which it sounds like the case), you can take a risk
tile direct using an S2 Greenscreed
https://www.tilersforums.com/forums/tile-adhesive/ before the screed has fully cured, or lay a vapour barrier such as ditra matting (preferred option) fitted with an S1 flexi
https://www.tilersforums.com/forums/tile-adhesive/ and use the same
https://www.tilersforums.com/forums/tile-adhesive/ to fit the tiles on top. The expansion strip also needs to split the ditra.
But again, your tiler should know all this, otherwise you shouldn't be letting him near it.
See? Not as easy as asking "what
https://www.tilersforums.com/forums/tile-adhesive/ do i need?" is it........ it all rests on the correct prep.
Examples of the above materials: (i'll stick to BAL as its one of the top brands and easily available but others are available such as Mapei and Tilemaster)
Flexible levelling compound: BAL LEVEL-MAX
Primer: BAL APD or BOND SBR
Anti-Fracture matting: BAL RAPID-MAT
S2 Flexi
https://www.tilersforums.com/forums/tile-adhesive/: BAL GREENSCREED or SINGLEPART FASTFLEX
S1 Flexi
https://www.tilersforums.com/forums/tile-adhesive/: BAL SINGLEPART FLEXIBLE (slowset) or BAL RAPIDSET FLEXIBLE FIBRE
Good luck.