Penthouse floor plan - Is it that practical?

Hmm, that doesn't sound so great. Which stone is then recommended for the interior walls on the [OG], although that would also affect the [EG] in the same way.

Does this sound issue not affect the exterior walls? Because they are built thicker?

I would definitely rotate the staircase by 90 degrees, relocate the passage, specifically by partitioning it off from the utility room with a properly deep built-in wardrobe. Then you have a clean hallway without the utility room stuffed with laundry and heating.

So the walls on the upper floor should rather be made with 17.5?

For whom or what should that be good? I suspect a rafter roof and that the structural engineer will still increase the wall under the ridge to 17.5, but I don't see anything else needed there.

17.5 lime sand brick is unfortunately not that generous. Because it is also mostly hollow on the inside today... (2-3 vertical tubes).

So what? - as a concert arena for Metallica the "tubes" are too small, what is supposed to take place in there?

That's also a good point. However, then we have a long hallway in that area. I'm still unsure how that will look.

I don't quite understand you. First you ask what it's supposed to be good for and then you write that it will happen that way. Well... I wrote that because said the walls were too thin from a soundproofing perspective.
I don't understand the second paragraph.

I don't quite understand you. First you ask what it's supposed to be good for, and then you write that it will come to that.

I only see a wall there that I would have made thicker - because I expect that the structural engineer will recommend it. Otherwise, why would anyone make walls thicker there?

the walls would be too thin from a soundproofing perspective.

I also only had 11.5 cm towards my younger brother and I'm still alive. I find this whole fuss (actually only a diamond is hard enough to block sound and sand-lime brick is basically already a compromise) utterly exaggerated. The objection that the brick is hollow is true - but not the conclusion that this is disadvantageous from a soundproofing point of view.

If you don't have siblings practicing drums, a standard wall isn't too thin. Non-load-bearing walls with 11.5 cm are completely sufficient.

Most people who write about sound in builder forums are simultaneously proud of their "four minus" in physics, don't differentiate between different types of sound, frequencies, and transmission paths, but simply once read a comparison table in some brick manufacturer's brochure that basically says: You have to buy our brick, for other bricks you either need meter-thick walls or earplugs. And then they post this nonsense further.

Ok. Then I will wait and see if the structural engineer requires the wall to be bigger and if not, I can still think about it later.

What I also noticed: I think the garage should be a bit wider: about 7.60 m, because I calculate 2 m per car, between the two cars 1 m - 1.20 m to get through with the motorcycle (the current one is 0.8 m wide) and on both sides 1.20 m each to comfortably get from the door of the utility room into the workshop on one side and on the other side possibly still hang winter tires on the wall and, of course, always be able to open the doors without problems.

A bit longer would also be nice, because I expect a vehicle length of 5 m. That leaves 25 cm at the front and back. On the side towards the utility room that is inconvenient, because you also want to get through to the workshop sometimes.
That the trunk cannot be opened is clear to me by now. I don’t think it’s reasonable to plan an extra 1 m for that.
So now I could either recess the wall about 0.5 m halfway or completely for the unobstructed passage from the utility room to the workshop and to the second car. That will make the workshop smaller, but there is no other way.
Because the alternative would be not to align the workshop flush with the house, but I think that would not look good.

By the way, the motorcycle has to fit into the workshop as well. Initially, it was actually planned to place it in front of the second car, but then the wall to the workshop would have to be moved even further and then the workshop would be a huge tube.

Just now I thought, one could also just design the workshop half as big.
Leave out the wall in front of car 1 (the right one) and place the bicycles there (they have to go somewhere too) and the motorcycle and keep the workshop as a workshop.

What do you think about that?