Soundproof a floor from above

[noone70]

We are adding an extension to our villa, and in it, we will have a rental apartment in the basement.

We aim to achieve two things regarding the basement:
1. Maximum ceiling height in the basement, as it is already only about 205 cm in height, so soundproofing the ceiling is not an option.

2. But the most important is sound insulation.
The floor structure consists of 220 mm beams spaced at cc60 with noggings.

For various reasons, the level of the floor structure in the new section is about 7 cm lower than the floor level in the existing section.

After parquet and underfloor heating boards (14+22 mm), there will be about 25 mm that we need to raise further to align the floors.

How do we utilize those mm to maximize sound insulation?

My "idea" is 2 layers of gypsum/floor gypsum and then the floor chipboards.

Alternatively,
Floor chipboards followed by self-leveling compound.

 

[Allmänobildad]

Two layers of plasterboard provide better sound insulation than particleboard and leveling compound. It also gives exactly the extra 25mm you need. I assume you have already considered mineral wool in the joists.

 

[noone70]

Two layers of gypsum provide better soundproofing than chipboard and self-leveling compound. It also gives exactly the 25mm extra you need. I assume you've already considered stone wool in the flooring structure.

Can I use regular wall gypsum or does it have to be floor gypsum? I mean, it's going to go on chipboard later anyway.