New Member looking for help with flooring

[Kev42]

Hello, I am looking for some some sound advice on the following, I will explain as best I can, apologies in advance for the droll !: -

I am fitting out a new upstairs bathroom in an old house (circa 1900's so well settled)
I have removed the old floorboards and replaced with 18mm WBP Plywood direct to joists (screwed every 150mm)
The floor (approx 4sqm.) is a little uneven so would like to self level prior to tiling (tiles are to be a Quartz Compac tile)
My question is two fold: -
I am thinking of using the Ditra Matting but am unsure if this should be laid prior to laying the self levelling compound or after? or maybe don't bother with Ditra and use a highly flexible tile adhesive.
Also is the 18mm WBP sufficient or should I lay another layer of WBP or possibly a layer of cement board?

Thanks in advance

Kev

[Bri]

Cement board on top of the ply if you can, SLC first (SLC ontop of cement board) then Ditra ontop of that.

[trevortine]

Hi kev, seeing as you have removed floorboards couldnt you have levelled joists with packers before laying ply?

[Dave]

I would advise the use of a polyurethane type adhesive with Quartz type tiles.. Some do not like the moisture from normal flexi rapid sets etc..

Mapei Granirapid S1 or Mapei Elastorapid S2 would suffice.

[andy8758]

Hello Kev and welcome.

I think Trevortine has the best idea if you want a level floor. Sounds like you have done very thorough job with 18mmWBP and screws at 150mm intervals - so there should be just usual flex with floorboards - follow Daves advice with S1 or S2 adhesive.

Ditramat soaks up horizontal flex (i.e. concrete cracks) not vertical flex (i.e. flexible floorboards) - so not necessary in your case.