Engineered wood flooring height difference between rooms. Underlay question.

[pr1970ster]

Hey All,

We have a new kitchen through lounge living area that is divided by pocket doors but with continuous engineered 16mm thick wood flooring. We are having electric underfloor heating on the kitchen side under a leveling compound screed over 25mm plywood and the lounge area/hallway is just 25mm plywood. Because of the underfloor heating there will be a height difference (5mm+?) at the pocket doors wall.
The builder thinks that having a thicker underlay on the lounge side may cause issues later on when its compressed over time with traffic and cause gaps in the boards. And is suggesting we level compound the whole lounge/hallway so its all the same level. The area is about 27m2, the kitchen/dining is another 25m2.
Any suggestions the best way to do this? I did come across TECHNI-BOARD which is 5mm thick underlay compared to the 1.8mm thick underlay for the underfloor heating. Would this work ok? or better to do the leveling compound suggestion.

Thanks

 

[blup]

Had engineered floor over cement screed in kitchen continuing over underlay in lounge (over suspended floor) and no change in 12 years despite minor difference in levels.

That said levelling it all is a neater job

Blup