Floor plan optimization of a single-family house with a basement on a small plot

that is on the list to ask the seller about

Who is the seller? Private individual or public corporation (municipality, water association, etc.)?

I can't quite imagine that it really belongs to us

I can hardly imagine that anyone would want to keep that - or that a third party would want to buy it. Especially since it would have to be burdened with access and setback easements.
Incidentally, it would give you about 70m² more plot area. Considering the tight floor space index without any possibility of exceeding it through ancillary facilities, you should definitely do everything possible to buy the strip.
Regarding the parking spaces and garages, it is as I suspected. These are not permitted outside the buildable areas. However, there is buildable area at the planned southwest boundary. Since I don't care about the sun, I would build there. So 6m carport with 3m tool shed on the boundary and then the main building. Of course, the garden would then face northeast.

Or a really stupid idea?

I think so. With a white bathtub even insanely so. You bury a floor only to dig the windows out again and additionally create a complicated second entrance. If it’s about the tower look—which I don’t understand—buy the "green strip" and build on a slightly larger ground floor with a full attic floor.

Who is the seller

Private, a small GmbH, which - I would call it "closely related" - to the development company...

Well, if possible, we would of course like to take the strip as well, I had previously thought that it would not be included, since the parcel stretches so long and I therefore did not assume that it would be shared... see plan



Although you are of course right, the dashed property line runs through there - definitely something to clarify, I absolutely agree with you!

But there is buildable area at the planned southwest boundary

No, unfortunately not quite, since the property is still divided in the middle (originally it was supposed to be one, we would have taken it completely... :confused probably a 3 m setback area will also be required here in the new development plan. So unfortunately we cannot speculate on that yet...

But I see the essence of your concern - basement to be very carefully considered given our circumstances

How is the development in the neighborhood? Our house does not look like a tower block The costs of the tower are more manageable and less risky. Especially with a tight budget, that is not a luxury. And I have to say the first few months after moving in were tough. So many bills kept coming one after the other or purchases. Lawn mower, rake, etc. We had already doubted our planning.

How is the development in the neighborhood?

To the west 1.5 stories and old farmsteads, partly 2.5 stories, to the north and east no development, only allotment gardens, pastureland and fields, in the southeast the new development area where everything from bungalows to 2 full stories is allowed, to the south 2 multi-family houses 3.5 stories, otherwise 1.5 story single-family homes.

On average across the whole place I would roughly estimate 1.5 stories...

Then it should work. Our neighbors are just as tall and we have a steep slope behind the house

Hm.... I just read the last posts and took @Escrodas's suggestion to heart. Besides, although I don't like basements, I could relate with you and with three children did see the basement after all. However, the final price is against it. The roof is already there anyway.... Maximize the height, use the attic as storage space (replace the basement stairs with attic stairs) instead of a double carport, have a shed for the man's workshop and the kids' and garden stuff... A south-facing garden is also nice, especially in winter... for the sundowner one could plan a second terrace between the shed and the house... Yes, this way it could become an affordable property.