Concrete and timber floor

[TonyS82]

I am going to tile the bathroom floor but have a question about flooring. Most of the floor is screed on block and beam, then under the dpm in the picture is the original brickwork exterior wall and then about 12inches of timber floorboards. it was originallly covered in 6mm ply which i intended on replacing with 6mm no more ply and laying self levelling over the entire area.
I dont think the adhesive works on plastic dpm so how best am i to secure it to the floor. i was going to screw it to the timber floorboards but im worried it will be loose on the brickwork.

thanks

 

[sxturbo]

Can you not poor self leveling compound to take out the 6mm height difference and level the floor at the same time?

 

[TonyS82]

I wanted to get something down to secure the floor boards. i guess i could cut the nmp back to just the floorboards and lay self levelling over the while lot?

 

[Notch7]

It looks risky tiling over 2 different substrates.

If it was me I'd use a decoupling mat like ditra over the whole area first.