snapperpb

Got it thank you! Does it matter if my floor rises above the the baseplate of the wall frames when its finished?

Yeah it's 1300mm to the soleplate in that far corner BUT it's almost level with soleplate in the bottom left (not pictured). Is it a problem if my final floor height is higher than the soleplate? (Redbeard the roof is clay, frame probably isn't professionally built I think it was the old owner)

@TommoUKThanks for this, I was wondering about insulation under the sand & cement, but doesn't that mean I'd need 35mm minimum depth everywhere? (The high point of this slab is almost level with the base plate of the frame)

We have a garden shed I'm converting to an office. The slab has sunk in one corner (I've fixed the problem with the foundation). You can see from the pics the back right corner is sitting about 13cm below the bottom plate of wall. (Whereas the closer left corner is almost about even with the base plate) What is the best way of prepping this floor for tile? My current plan is: DPM paint + DPM runner along the side Foam in edge cracks Sand & Cement Screed Tile backerboard with insulation (is this needed?) Tiles Does this sound about right? I'm in the UK, not much frost heave or very low temps, but of course there's damp. I'm going back and forth on electric underfloor heating here as well, if anyone has any takes!