W
White Room
I remember over 40 years ago screed straight onto block and beam....
a block and beam floor is a raised floor not connected to the ground and vented so you have 30 mm screedHi. I can see how that would be very rigid but if I've got it right I'd not have any insulation under the floor and I'm not having under floor heating.
I'm not happy tiling into ply and I've made it clear I'm happy to pay to have the floor ripped out and replaced with Marmox at my cost! I want a job that is done correctly and 100% not to fail through inadequate substrateNo matter what the substrate, ply is not a suitable material to tile on to!
A professional tiler who is up to date with latest practises would know this.