Sound insulation VDI Guideline 4100 & DIN 4109 in prefabricated house construction

I have had exactly the same thought. As a layperson, you can read a lot and ask in forums like this - and yet there are always details that could have been done much better with little effort. Apparently, there is no profit to be made from soundproofing the pipes, so it was not an issue for us either.

we were looked at strangely

Well, running the sewage pipe from above through the dining room is rather unusual when aiming for a reliable planning.

the toilet hangs on the wall to the children's room

See above. A planner ("architect") actually learns in basic studies that such things normally do not work. But that's how development goes when floor plan creation increasingly becomes amateur work.

The HVAC trades provide excellent professional literature and guidelines on the subject, so that such things should no longer occur or only at the explicit request of the client. If one understands their craft.

See above. A planner ("architect") usually learns in their basic studies that such things simply are not acceptable. But this is how development goes when floor plan creation increasingly becomes amateur work.

There are two explanations for the mess in one paragraph: 1. The client considers the architect a waste of money and thinks "I can handle that bit of floor plan myself"; 2. It ends there because then, in the form of the general contractor’s draftsman, a second-opinion body is consulted who, at the behest of their employer, has no opinion (and would not be qualified to have one). Consequence:

Well, running a wastewater pipe from above through the dining room is rather unusual considering the demand for a solid, sound plan.

The wastewater pipe is a result of the fact that the client liked a floor plan for the upper floor of a different Pinterest house than for the ground floor.

Just saying: we were at the architect ... nothing self-drawn. However, it goes like this: Client: "I wouldn't want the bedroom right in the south in the blazing sun and adjacent to a children's room, would it be possible to swap the bedroom and bathroom?" Architect: Yes. There's no "that's dumb because you don't run the wastewater through the dining room" or "if it has to go through the dining room, then we'll insulate it..." There’s nothing, even though we told X how important soundproofing is to us! With the casing, by the way, it’s no problem... It's only the shower you hear rushing... And about the toilet: that was a draftsman who deserves to be lynched. Then a 12 cm wall... thanks a lot... 24 cm would have been possible for 20 euros more...

For example, with us the toilet flush is right next to the guest room, so you could have said something about that without any ifs or buts.

Schwörerhaus has insulated pipes and sewage lines, only probably not the flush. But as you say, where else could you have put the guest room. It's not like there are 200m2 on one level.

What also annoys me is that the wardrobe for 4 people is way too small.

I discovered the forum way too late, many things that are discussed here daily in floor plans simply ring true.

Everything works but maybe more could have been made out of it.

No. The first sentence of the reasoning states:
"Which sound insulation is owed for the construction of semi-detached houses must be determined by interpretation of the contract."
Later the note:
"Indications can be derived from the regulations of sound insulation levels II and III of VDI Guideline 4100 from 1994 or Supplement 2 to DIN 4109."
The 25-year-old VDI 4100:1994 naturally no longer applies and by no means corresponds to the state of the art. The 4100 was revised in 2007 and 2012, the 2007 version was withdrawn, but was (and is) still applied for a few years.

Good luck. No university of applied sciences builder can provide that for you. Many solid builders are also likely to decline or charge considerable extra effort.

Thanks for the clarification regarding the BGH ruling.
In the wiki it definitely comes across as a bit more "pro client," I think, which also surprised me.

It is difficult for the client to prove what is actually "owed" if nothing concrete was agreed. The measurable REQUIRED often remains unclear in reality for the layperson. And that makes me uneasy.

Thanks for the hint that Sound Insulation Level III implies an extreme additional effort, even in solid construction(!). For me as a layperson, the latter is not self-evident.

My general contractor apparently calculates an amount of >20,000 euros in additional effort for Sound Insulation Level II (roughly estimated), but it is hard for me to assess whether that is realistic. At first glance, that seemed to contradict the BGH ruling and drove me to this forum.

To determine the REQUIRED standard, I as a "friend of many words" (I like the euphemism, and it fits ) asked the general contractor about the details of the party wall and... indeed received an immediate response.

I won’t post the pdf here but will describe the structure in bullet points from inside to outside (at one half of a semi-detached house):

1. 12.5mm diamond gypsum fiberboard (GKFi)
2. Vapor retarder
3. 15mm OSB board
4. 110mm mineral wool insulation in a 110/60 mm timber stud (spacing <625mm)
5. 2x18mm gypsum plasterboard GKFi
6. 50mm air gap up to the boundary of the semi-detached house half

ops: Air?! (possibly the so-called drum effect threatens, wonders the layperson...)
Point 6 is replaced by mineral wool insulation in the edge area (i.e. only near the outer walls adjacent to the party wall).

That air insulates poorly is clear to me as well.
Instead, mineral wool insulation everywhere where there would be air?
Or something with "more mass"? EPS or something like that?

However, measurable values (other than material thicknesses) are very limited there. Which sound insulation level is achieved remains unclear to me, and as a layperson I can hardly assess the sound insulation capability.

I have stirred up enough dust; now it’s time for a little more "depth".... which I unfortunately cannot offer myself as a layperson maybe soon we will scratch the surface or possibly go deeper?