Floor plan and space issues for a single-family house

Development plan/restrictions
Size of the plot: 486 sqm
Slope: flat

Building window, building line and boundary: "neighboring development"
although I can't really see a clear pattern here.

Requirements of the builders
Style, roof type, building type: gable roof, single-family house
Basement, floors: no basement, 1.5 floors
Number of people, age: 2, 24 years

House design
Who designed the plan: friend who is a structural engineer

Hello everyone,
I am newly registered here in the forum and would like to get some opinions and possibly suggestions for the floor plans.
Unfortunately, the plot is relatively elongated (approximately 16mx27m)

Currently, there is a house ready for demolition in the same position.

The room layout is also limited by the fact that at least on the boundary side no windows are possible on the ground floor.

I look forward to any criticism, objections and tips.

Have you ever spoken to the building authority about the buildability? [Traufgassen] were common until the 19th century, today they are almost always prohibited. So either you build on the boundary or you keep the setback areas or – which I consider unlikely – the authority grants you an exemption. The same applies to the western neighbor: either attach or keep a 5m distance.

Building in old village structures is quite complicated. If the friend is your age, he will probably have to learn a lot. However, you are the ones who pay the learning costs. Basically, you should consider how much the friendship is worth to you. Offering help is good, but I advise against taking over the project.

Requirements of the builders Style, roof shape, building type: gable roof, single-family house

I see a house with two 2-room apartments.

It is initially about a building inquiry. Since the old house is ready for demolition, I wanted to submit a building inquiry to make sure that I am allowed to build again as before. If I had to keep a 5m distance on the right and left, only 6m would be left. How is this usually handled when there is no development plan and all other houses in the street are also built on the boundary? For example, the neighbors have the house side on the boundary and an L-shaped barn attached, of which the gable end also stands on the opposite boundary. Yes, the house is intended to be potentially divisible later if the space is no longer needed.

How is this usually handled when there is no development plan and all other houses on the street are also built on the property line?

Then it is a closed building structure and the new building must also be on the boundaries. However, your eastern neighbor is not on the boundary but at a distance that is no longer permitted today. In this case, the building inquiry is exactly the right way to find out the authority's point of view. As mentioned, the planning law assessment in existing buildings is very difficult and often leads to deviations from building regulations, which then need to be well justified.

Then it is a closed construction type and the new building must also be on the boundaries. However, your eastern neighbor is not on the boundary but at a distance that is no longer permissible today. The preliminary building inquiry is exactly the right way to find out the authority’s point of view. As mentioned, the planning law assessment in the existing stock is very difficult and often leads to deviations from building regulations, which then need to be well justified.

Thank you very much for the information. So the house should rather be placed directly on the boundary and not like the neighbor.

The civil engineer friend has been asked first to take care of the part of the preliminary building inquiry so that the old house can be demolished as soon as possible.
Its condition is more than alarming.

The floor plans above are hand-drawn on the position of the current house.
The first goal is to establish a suitable floor plan (room layout and size, etc). Nothing is final yet, which is why I want to hear further inputs and opinions here.