Is the plot suitable for a narrow house for 5 people?

You have unfortunately crossed out the reference height in bold green. But a house with that number of rooms is definitely possible.

With 10 years until the first child moves out, I would build based on the needs NOW and when the third child has moved out, sell the house again and get a house that fits the next phase of life.

Yes - that’s what we thought as well. 2.5 stories probably won't be barrier-free. We are calculating with 15 years (in case we still have to bridge the time of studies).

Hello , welcome to the forum,
I would suggest asking the building authority whether a single semi-detached house as drawn can be approved if connected to the garage.
If yes, then there are plenty of functional floor plans on 12x7m.

Thank you! And yes – we definitely wanted to get in touch there. I can imagine a semi-detached house in a full duplex of that size over 3 floors. However, with such a narrow single house with semi-detached house floor space, I found that difficult. I’m also not sure whether one might even have to include the garage in the gable – see point 1.5 of the development plan text below.

But: We should probably really talk to an architect. The possibility has come up for us somewhat suddenly.

7 x 12 is not narrow at all? You can easily get over 160 sqm of living space.

Unfortunately, you have crossed out the reference height in bold green.

But a house with that number of rooms is definitely possible.

Oops – here they are. Thanks!

This also gives me the opportunity to show the other two plots (light green dots on the left and in the middle).

Currently, we are considering whether a larger bungalow with a living basement (perhaps in the style of a granny flat) would be an option for us. The left plot has a nice, unobstructed garden but can only be built as a single story. In terms of accessibility and possible future rental, that would of course be advantageous.

Regarding the free floor space index: there probably wouldn’t be anything possible with the attic conversion, right (NRW)?

The middle plot could be built on in a very classic way, but it has a slope of 0.7 m in the garden down to the relatively open street. However, it would certainly be feasible.

Difficult decision.

I consider that rather difficult. 7 rooms distributed over a bungalow area? And if the basement apartment only gets light wells or courtyards, then in my opinion that is a less high-quality living space than building narrow upwards. Because then you have a view and light.