Land use for semi-detached houses or halves of semi-detached houses

that a semi-detached house with a shared technical room (only accessible from the outside) is not possible in the case of a real division

... I do not see it that way. With an appropriate easement, it could definitely be possible, although I would not place this room across the boundary, but clearly within one of the halves. I had already advised against the Janus mirror clone (and specifically cited the example of to illustrate such unequal twins - with a corner plot, however, this is easier to implement). I assume here that one would find a more square-like half and a more elongated half and divide the two parts individually. In this context, or to facilitate this, I also advise against fixating on an equal division by size. Thus, I also quite certainly see an architect project. Ultimately, my advice also implies planning the development first and then the boundary line.

The building application must be submitted by each building owner themselves.

No. If you trust each other, you can form a building owners’ community and appoint an authorized representative.

Bedrooms and technical rooms are not used jointly.

Bedrooms yes, technical rooms kind of – it depends on what is housed in them. With a combined heat and power system, you can supply the entire neighborhood with heat. Depending on the implementation, the building permit authority has little to nothing to do with that.

Realteilung means everything for oneself.

That is, IMHO, the most sensible way, but not legally necessary in terms of building law. Between a multi-family house with rental apartments and two completely independent single-family houses, there are many configurations whose advantages and disadvantages depend on local conditions (property, development plan, etc.), the budget, and personal preferences and compromises.

No. If you trust each other, you can form a building owners' association and appoint an authorized representative.

Ah. Ok?! Then I think I confused the OP with my ignorance, but I believe I spoke in his interest, since...

That is, IMHO, the most sensible approach, but not legally necessary.

... he spoke of a real division or prefers it. Personally, I would give the advice, although (or precisely because) there is a family relationship here, to divide it physically, as relationships can change especially among relatives.

With the appropriate easement, that could definitely be the case

That is something we would rather avoid.

Ultimately, my advice also entails planning the development first and then the boundary line.

That is very good advice, because it may indeed make sense to design the halves somewhat differently in order to account for certain parameters such as unfavorable lighting. Top!

That is very good advice, because it might indeed make sense to design the halves somewhat differently in order to account for certain parameters such as the unfavorable exposure. Top!

I had already "feared" that at this point I might lose acceptance of my advice due to the "reversal" of the process – but this is not my first building planning thought experiment (rather the thousandth), and I consider it almost impossible to implement in a "same width and same depth" corset that the sun rises in the east for everyone.

After just under a month of further research time and obtaining offers for the demolition, I would like to continue this thread a bit further.

I have taken the comments from to heart and have "painted" a bit:

1. 2. 3. 4.

Please don’t take the sketches too literally. Things can still be shifted if my naive ideas don’t fit. Also, how the garages could/should be positioned I have not considered for now, but simply placed them at the property boundaries.

Variant 1 – The Standard: Probably doesn’t require much explanation. The right half simply has relatively little light in the entire living and kitchen area in the evening. The same applies for the left half in the morning.

Variant 2 – Offset: This way, a window on the west side could provide a bit more light for the right half in the evening!? Unfortunately, this is somewhat disadvantageous for the lighting of the terrace on the right half in the evening hours.

Variant 3 – Offset & Rotated: An attempt to eliminate the disadvantage of variant 2 while maintaining its advantage.

Variant 4 – Free: No idea if this is even realistic. Because here you would presumably have to have two different ridge directions. And whether that complies with §34 on the street remains questionable.

What do you think? Do you have further ideas for a variant that creates good light for both sides? I think you cannot serve both sides with light in the same way due to the fact that the houses are built attached to each other.