Ditra over SLC over ply over ply - Tile Advice

[Greg]

(I know similar questions have been posted before but they're closed for follow up questions)
I have a 1930s house where I'm renovating the bathroom - a complete refit that includes removing all the squeaky, somewhat rotten (in places), but crucially not-level floorboards and replacing them with a 12mm ply sub-floor adjusted to make the floor as level as I can. Then glued and screwed (every 200mm) over that is 18mm marine ply. I'm planning to use the least SLC I can get away with, to minimise the size of a step into the bathroom. Then over that is a Schlüter DITRA uncoupling layer/membrane and then tile over that with 600mm sqare 10mm tiles.

The SLC is Ardex Arditex NA (powder & latex)

Am I correct to use minimal SLC?
Will the uncoupling layer protect the tiles if the SLC is thin and if not, what's a minimum thickness?

Have I forgotten anything?

 

[hmtiling]

(I know similar questions have been posted before but they're closed for follow up questions)
I have a 1930s house where I'm renovating the bathroom - a complete refit that includes removing all the squeaky, somewhat rotten (in places), but crucially not-level floorboards and replacing them with a 12mm ply sub-floor adjusted to make the floor as level as I can. Then glued and screwed (every 200mm) over that is 18mm marine ply. I'm planning to use the least SLC I can get away with, to minimise the size of a step into the bathroom. Then over that is a Schlüter DITRA uncoupling layer/membrane and then tile over that with 600mm sqare 10mm tiles.

The SLC is Ardex Arditex NA (powder & latex)

Am I correct to use minimal SLC?
Will the uncoupling layer protect the tiles if the SLC is thin and if not, what's a minimum thickness?

Have I forgotten anything?

Latex first then ditra if you have these materials to hand. If not, 22mm ply sub floor, 6mm cement board and tile

 

[Greg]

Latex first then ditra if you have these materials to hand. If not, 22mm ply sub floor, 6mm cement board and tile

Thanks
Maybe this image more clearly explains what I mean.
I've already got the 12mm subfloor and 18mm Marine ply down (glued & screwed). So, if I understand your response, I'm right to use the latex based SLC over the ply, then the Ditra, then the tile. The remaining question is can I go for the thinnest possible amount of SLC where it may even fade to zero (options A &/or B) or is there a minimum thickness (option C)?

 

[hmtiling]

You can feather na out so options a and b. It doesn't go very deep without aggregate though, 15mm if memory serves.

 

[Greg]

Thanks hmtiling. And sorry for the missing 'g' in 'exaggerated', in my sketch.