Join Chipboard floor to concrete floor - Advice on approach!

[JohnTUK]

Hi - first poster here and looking for some advice on joining an existing concrete floor to a new chipboard floor.
Basically I've knocked through into an unused lean to and the plan is that this will now become the new downstairs WC. Given the difference in floor levels a suspended timber floor was created with 18mm P5 moisture resistant chipboard as the subfloor (as per building control officer guidance). I am looking at having the same flooring (possibly vinyl) go between the two rooms.

The room that I'm going from (utility room) has a solid concrete floor and I wanted to understand from people what's the best way to join them as there's a 1-2mm gap between the two. My main concern is that if I lay the same floor there will be some kind of cracking/tearing as this is effectively a 'weak spot'.

Do I fill the gap with some kind of screed?
Do I leave it as it's not enough to worry about?
Do I ditch the idea of 1 single continuous floor covering between the two rooms and install some kind of threshold between the two, effectively going over the top of the small gap?

Advise would be appreciated!

J

 

[foxhole]

Glue / screw down 9-12mm ply over the lot then you have a stable base for vinyl.

 

[chappers]

even something thinner if the gap is that small, but even a gap that small will probably eventually show as a line in the vinyl.
For any other type of flooring I wouldn't bother, will only be a weak spot if either floor is moving.

 

[jj4091]

Personally I would not have thought it would be a problem, but I believe if professionals are laying vinyl over old floor boards they would lay thin ply or hardboard down first in order to cover any gaps between the boards that the vinyl might eventually sink into & show up as tram lines in the surface.