divide a long, narrow plot

You don’t want to build 2 semi-detached houses, but 2 houses with 2 residential units each? If you want to build 1 semi-detached house with 2 semi-detached units each containing 2 residential units, it would be one continuous building – that would fit the image better.
Your parking spaces are also drawn too small. Clarify how many parking spaces are required per residential unit (parking regulations if available). 4 parking spaces at 2.5 m each are often not approved in a row – better plan with 2.8 m per parking space.

Hello Wastl,
yes, you are right. My choice of words was not correct, the correct term is 2 houses with 2 residential units each.

The continuous building results in very narrow, long apartments (so that all apartments also have a southern exposure).

Width of the parking spaces
I used the neighbors as a reference; their parking spaces are about 2.3–2.4 m wide. Can one not refer to that?

Building structure
As a distance between the houses, we roughly calculated about 8 m. If I compare that to the new development area in town, that is already a quite common constellation, which is even undershot there.
Of course, it can’t be any different there, since the plots are naturally much smaller today.
But still, here for comparison, the 8 m are each marked in yellow (southern orientation of the houses).

Regardless of the implementation: The colleagues from the emergency services are not pleased when they have long walks. As for the 8m - has the clearance distance been adequately considered?

At first we thought of a multi-family house (2 stories, 2 apartments each), but just based on the dimensions it would end up as very narrow, long "tube" apartments.

Does anyone understand this? If you combine both planned houses and connect them with a staircase, you have almost the same dimensions for each residential unit as with your two houses – only then you have a multi-family house with 4 residential units.
What would the requirements be for a multi-family house with 3 or more units?

In the surrounding area (on the other side) there are mostly single- or two-family houses or bungalows. Therefore, here is a larger section from the aerial image.

From Google? Or where is the source? We ask for source citation!!!

You must not compare apples and oranges. First check if there is a development plan for your area. What the neighbor is building on the other side may be absolutely irrelevant to you under certain circumstances. If the street is the boundary of the planning area, there may also be bungalows on the opposite side,... If you are at the building authority anyway, check if there is a specification for parking spaces. These are often relatively new, so they do not apply to existing buildings. AND: If the neighbor builds incorrectly, that does not entitle you to build incorrectly as well. Therefore: Don’t look too closely at the neighbor, but rather ask the building authority. It seems to me as if your neighbors have built very close to your property. Are there any easements on your property regarding this?

Sorry if this comes across a bit harsh, but if I were you/yours, I would urgently consult an architect. I can still tolerate it when you design and tinker with your own house, but with such a construction project, we're quickly talking about sums in the high six-figure range, if not higher. On top of that, there are completely different requirements for multiple residential units, but especially also regulations (development plan, etc.) that you as a layperson cannot really oversee.

We (my parents and I) are currently at the beginning of such a project ourselves, and something like this can no longer be compared with conventional single-family home construction. It's great if you put thought into it. But just the statement that the apartments are becoming tube-like shows that it would be worthwhile to take the step to the right planner.

We are currently planning our own house, it apparently measures 18 x 7-8 meters, and with good planning, nothing looks tube-like at all.

In your initial post, you speak of 2 houses measuring 11 x 9.5 meters each. Assuming you make one building out of it, the building would then be 22 x 9.5. To enlarge the access + garden area a bit, I could imagine making the building longer and narrower. For example, 25 x 9m. If you plan 2 residential units per floor and then place the entrance + staircase in the middle of the long side (3m wide), the staircase basically divides the building. So you have a floor area per residential unit of 25m - 3m staircase / 2 residential units = 11m/unit --- 11 x 9m.

Not that far from your original dimensions.

Even if you want 4 residential units per floor and go for a total length of 30 meters, the building is accessed by 2 staircases. So 30m - 2 x 3m staircases = 24m / 4 residential units = 6m width. So you have 6 x 9m per residential unit. But these would then be rather larger apartments or small 2-room flats.

Of course, this is just theory now, but I want to show you that a long narrow building does not necessarily have to lead to long narrow apartments.

Hello Dirk,

In the surrounding area (on the other side), there are mostly 1-2 family houses or bungalows. Therefore, here is a larger section of the aerial photo.

Hello @smartsufer,

is absolutely right, without an architect any further planning is completely pointless. The comparison with surrounding development areas/aerial photos does not work for at least 10 reasons (development plan, floor area ratio, floor space index, setback distances, parking spaces, fire protection, etc. pp.), therefore I also consider your conclusions from that to be not necessarily correct.

Nevertheless, I consider the plot to be quite buildable; we regularly oversee such projects here. But it is by no means trivial and since you need an architect anyway for the building application, it makes no sense to worry too much about a possible development, because an architect will take a look at it for 10 minutes and then will certainly be able to roughly say what can be done and what not in a 1-2 hour discussion.

Regarding ownership structures, the plot can also be subdivided in kind, thus creating more flexibility. This involves costs and must be taken into account in the planning (building completely first and then subdividing can potentially have significant building law restrictions!), but it is highly probable and from what can be judged with the available information, possible.

Best regards
Dirk Grafe