Sound insulation: Thickness of cavity insulation for interior wall?

Regarding decoupling the ceiling beams, I will talk to the carpenter tomorrow. The ceiling structure is as follows: (from bottom)
- 12.5 mm plasterboard
- 15 mm OSB
- 50 mm battens (installation level)
- wooden beam ceiling
- cavity insulation between the studs
- 22 mm OSB
- 20 mm thermal insulation
- 35 mm impact sound mineral fiber insulation
- PE foil
- 65 mm screed

If the beams have to be decoupled from the bearing wall, wouldn’t the 22 mm OSB also have to be decoupled with sealing tape? Or not, since that would create a cavity?

The interior walls are double-boarded anyway – on the studs each with 15 mm OSB + 12.5 mm plasterboard.

For the exterior walls, on the OSB of 15 mm lying on the studs towards the inside, there is an installation level of 6 cm. This is also double-boarded again – first OSB again and then plasterboard. I just don’t know right now whether the installation level will be insulated. Too much insulation is sometimes not good because of moisture. I also have to discuss this with the carpenter.

Hi, so with us, the installation level on the exterior walls is also insulated, and otherwise we have similar constructions of the walls/ceilings. We have been living in the house since the beginning of March and acoustically we cannot complain, of course there are differences in how people perceive noise, but we have really wild boys and we just enjoy the "quiet" here in the house.

Do you possibly have a few details? How and where was it decoupled? Especially in the ceiling area?..

- 15 mm OSB
- 50 mm battens (installation level)
- wooden beam ceiling

How is the connection between OSB/battens and battens/crossbeam designed? Is there a tongue-and-groove rail or suspension somewhere in between? I would personally prefer it that way.

Hi, sorry that it took so long.
So in the granny flat, the gypsum boards are screwed onto spring rails - instead of battens - (but don't ask me what exactly it was called), you don't hear anything from the guys there, unless they do sack racing or something like that.
Since we still had some of those rubber mats left over, they were placed under the battens in the living room and kitchen. The boards on the walls were also always pulled up and insulated all the way to the top.
The gypsum boards were screwed in normally, nothing special was done at the joints either.