Build an extremely narrow house with a width of 4.5 meters due to setback areas

For something so special, you should hire a good architect.

Are there no alternatives with you, or do you actually like it that way? I mean, you find something like that in many old towns, super narrow half-timbered houses, and people still live in them today. My great-grandfather had such a house; it then had different levels and many stairs. I somehow can't imagine it for a new building; in the old half-timbered houses in a half-timbered town, it at least has a quaint charm. In Quedlinburg, there are houses that are hardly wider than an adult's arm span. And there, the houses all stand in a row – with you, they would apparently be freestanding.

a you simply have very little space on two floors above ground and certainly don't want to waste it on a technical room.

has made no statements about the space requirements or the site situation (site plan with north arrow). And possibly the technical equipment could also be placed under the roof. But basically I agree, that requires an architect.

Or maybe possibly the option to cultivate land at one of the neighbors? Possibly for a payment? Then firstly it could be a bit wider, secondly there are many standard floor plans for semi-detached houses or terraced houses...

I currently have a plot reserved on which one could build a maximum of 4.5m wide but up to 14m long. Two stories.

That would be about 100 sqm according to the rule of thumb, or rather even less due to the unfavorable shape. But are these really facts or is the width calculated by naive subtraction? Even if the entrance could be in the middle, there would be almost only walk-through rooms inside. Accessed from a narrow side, you can forget it.

Are there house providers who build such narrow houses? A single build as an architect’s house would probably be very expensive. If you have experience, please feel free to add your floor plans as well.

Off the shelf, nothing will be good there. Such a thing will rather be expensive without an architect. The limitation to two floors is the problem, otherwise you would find plenty of examples in Tokyo.

We have been renting a similar house for about four years: it used to be a stable a long time ago, renovated and converted in the 90s. Half-timbered, interior dimensions approximately 4.20x14m. Living area on one level, kitchen/bathroom raised by two steps, with a cellar room underneath. Upstairs two rooms at corridor level (one is a walk-through room) and the third room also raised by two steps. Roof pitch around 70 degrees, with knee walls between 20 and 50 cm.

The house has a very cozy charm in which we feel very comfortable - however, things like walk-through rooms are practically unavoidable... It may work with one child, but with more, the dimensions hardly allow options to design it differently. Here all rooms are as wide as the house, except for kitchen/bathroom, which are therefore very narrow and offer no space for a guest toilet or a table in the kitchen. If I imagine our house as modern as possible, I would suggest, based on our living experience, roughly dividing it into 4 sections:

First quarter bathroom with recessed additional toilet (only one is not an option), second quarter entrance area with stairs, third and fourth quarter open living area... Then upstairs first quarter room 1, second quarter stairs/corridor/space for a desk, third quarter office/guest (room 2). Creating a small corridor here to avoid the walk-through room will be very challenging – at least if the room needs double-digit square meters. Fourth quarter room 3...

The question is whether one is willing to make such compromises when putting 500k on the table for a new build on a plot... After years we have decided that we do not want that and are now building new. If a walk-through room is not a problem for you, then you can live quite well in such a house! We find it very cozy. Of course, good planning is a given.