Ply floor depth?

[Heating one2one LIVE]

I have pine floorboards in my kitchen which I'm removing and replacing with plywood with tiles on top. The pine boards measure around 16mm. The problem I have is getting the floor from the hallway which is the pine to meet the new tiles and not have a huge lip.

Can you use 12mm ply or does it have to be 18mm minimum? The 18mm ply will already be higher than the pine and that's without the tiles and adhesive. Is there another solution for this problem?
Thanks to all in advance.

 

[foxhole]

You don't really have a problem , you will need a threshould to avoid damage to the tile edges , you simply install one with a chamfer to join the two levels.