Structural wood flooring -on- underlay -on- joist?

[Battor]

Hi,
I am planning to have 20mm engineered wood flooring on different floor levels, including 1st and 2nd floor (timber joists).

Since the flooring is structural (equivalent to dedicated chipboards), I can omit the chipboard to save money and space.
There will be underfloor heating (in-joist plate diffuses).

To minimise the impact sounds, we want some soundproof underlay between the joists.

Question: Can the underlay seat directly on the joists?

I think the weight will compress it too much over time and might reduce the proofing. Also, I am not sure whether between joists the underlay would do much dampening if it's not in a solid sandwich but only in contact with the upper wooden floor, and the delicate spreader plates of the heating.

Altenative?:
I could add a 6mm plywood on the joists, to lay the underlay on it, to have a more proper sandwich.
Would that work?


I would rather avoid adding too many thick layers, for saving on ceiling height, cost, and it just sounds pity needing twice structural layers of 20mm each.

If it's absolutely necessary to have the 18-20mm chipboard to lay the underlay on, then I might need to revisit the flooring choice.


Thank you,

 

[Battor]

Sorry if it was a silly question.
Some insulation vendor claim they can have sounds insulation boards (12mm soundproof material + 18mm chipboard bounded together), directly on the joist, but I feel that's going to crush the material over time.

Will it not?


Thanks,

 

[denso13]

Don't put insulation, sound or otherwise, between the ufh and flooring. That will adversely affect the ufh performance.