Raising floor level to match after knock through

[AP25]

Hi,
I recently brought down a partition stud wall that was splitting the conservatory. Now the floors dont match by about 18mm.
I want to have the same floor throughout. Am I OK to drill plug and screw plywood over the existing tiles and lay laminate over the top with an underlay? Would I need any DPM??
The tiles are ok, not perfect but I really dont want to have to rip them up.

 

[AP25]

Anyone?

 

[dazlight]

If tiles solid then that's a good way to go.
Or use a screeding compound with a liquid dpm too if worried about damp.

 

[AP25]

the issue I have is that the floor is 18mm out at the meeting point of the 2 rooms but is almost level at the entrance door. So i need to make a large jump at one end without making life hard at the other end

 

[dazlight]

I'd be going with a screeding compound then. Some battens to work out levels.