Very uneven subfloor - Impossible to have oak boards?

More expert advice please

Existing pine floor is very uneven - one corner of the room rises by 18mm over just 1.5m! Does this rule out ever being able to have engineered oak flooring? We can't take existing boards up completely as it supports a stud wall.

Could 20mm engineered oak be glued down to a plywood subfloor (with sufficient weight as it cures)? Could we 'pack out' the subfloor with fibre board to even out the difference over a greater length?

All thoughts will be very gratefully received

GW

20mm is more rigid than standard 15mm so can handle a bit more, but not that much. Weighing it down does not help though.

What you could do is easing the sloop further down with different thick plywood so it levels out and the new wood floor only has to tackle a "normal" sloop of maximum 3mm per meter.

Thanks WYL,

If I use different thicknesses of ply, would I need to add an additional top layer of ply so the contact surface with the engineered boards is smooth? This could raise the floor considerably...

I assume you would recommend floating the boards on 3-5mm foam underlay.

Thanks again for the help with this

GW