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

What do you mean by that?

Basically, you have already answered the question yourself, similar to Pinky0301. Honestly, this was just one offer from a prefab house provider where we had this distinction. All others have so far only offered us semi-detached houses. The savings supposedly come from filing only one building application, having one heating system for both houses, and the house being considered one order by the provider and not two as with two separate semi-detached houses. A somewhat dubious explanation was that one cannot assume that the halves would be built at the same time and then “the machinery” might have to run twice. But we definitely want to build at the same time.

It would be best if you also showed a cadastral extract of the property, then one can pictorially imagine the divisibility. Would both halves have direct access to the street?

No problem! After the division, both plots will have direct access to the street. The space indicated here for the building is only what would be possible at most considering the building encumbrance. However, we will not fully utilize this because our halves will “only” have about 115m² living space. As a little background info: It is a hillside location, so the property slopes upwards towards the back. Therefore, we will have to build with a basement (which will serve as the entrance level).

I also prefer the real division because it is one more contract .

Thanks for the explanations, that is very valuable input for us and somewhat confirms our current assessment. I will research the regulations regarding the bylaws to see how it is regulated here.

Is the cheaper price still given if both halves are not exactly mirrored but individual wishes are taken into account?

Yes, that would still be the case, although we ourselves are relatively united on the interior layout (except maybe the basement), so mirroring would certainly be within the realm of possibility.

If you want a duplex with different halves (size, layout) that from the outside still appears as a single unit, you are probably better off with a solid construction general contractor and architects for the planning beforehand rather than a prefab house manufacturer.

I am already curious about the talks with GCs. As a first step, we have already spoken with an architect about our project. Unfortunately, he could not provide any statement about more precise expected costs (which was not to be expected). He made us an offer for preliminary planning after which we would get the expected costs somewhat more detailed than a range of 350k-400k per half. But this would already be an investment of several thousand euros. So, we did not do that at first. Cost certainty is relatively important in our case.

Is it the case that for a build with a GC one should choose their architect for the planning beforehand themselves instead of taking the “partner” of the GC? It probably also depends on how the GC handles it.

Thanks for your answers, this is very helpful!

There is recently a note about similar topics here, but unfortunately the link does not work. Nevertheless, I have looked into it once; two of the five other threads do not lead further, the other three I will mention here:
and
by - in my opinion highly recommended, since I am not a big fan of Janus mirror clones (one half lacks morning, the other half evening) as well as
- however, there would be no equivalent street access there.
The one by has the slope reversed, meaning the incline goes toward the street.

Thank you for the service with the links and the hint about this forum feature. I have gone through the threads. I was able to take away some valuable tips and the realization about many things one should consider when planning the floor plan.

Unfortunately, building in the second row is not allowed on this property, which means the terraces will both have to be positioned almost exactly to the north. So there is not much flexibility in the orientation of the house. I found the note interesting that the right half may get less natural lighting in the dining/living room in the evening than the left half. I had not thought about that until now.

Another insight: use the search function better before asking and first read a lot.

I'll keep it brief:

The saving supposedly comes from only submitting one building application,

Every builder must submit the building application themselves.

having one heating system for both houses

In a real division, each builder builds for themselves: bedrooms and technical rooms are not shared. There is also no shared cat flap - fire protection regulations forbid that.

and the house as such counts as one order for the provider and not as two for two separate semi-detached houses.

No, two builders, two contracts - one with you, one with the neighbors.

But we clearly want to build at the same time.

With the same builder, this means: start first with the crew on the left, after the masonry the right side. Step by step... the builder may give you 1 or 2% by saving one trip for scaffolding setup and removal, but even the assembly and disassembly is individual for each half.
The only real saving is land area... negligible at your size, and the finishing of the partition wall.

In the case of a real division, each builder constructs for themselves: bedrooms and technical rooms are not used jointly. There is also no shared cat flap – the fire protection regulations prohibit this.

I conclude from your statement that in a real division, a semi-detached house with a jointly used technical room (accessible only from the outside) is not possible at all. Thus, a semi-detached house would already be excluded if we consider the real division as fixed. These are exactly the kinds of questions I want to have answered, thank you all for the quick responses!

That's right. If together, then a two-family house in semi-detached construction, but no real division. Real division means everything for itself. However, it does not exclude a semi-detached house, i.e. two houses attached to each other. Ideal division is done when the building regulations stipulate a certain size of a unit as the minimum size of a plot of land, which is not achieved with a real division.