Development according to §34 - Large house with steep roof required

How do you plan garage / car parking space? 2.5 m distance is not that much

In front of the house. Basically like at house no.16 as a pure parking space. No garage.

I always wonder how people come up with the idea of buying a semi-detached house and planning the new build as if there was no conjoined twin.

We do not do that at all. If the costs for such an "unnecessary" roof just shoot up like that, one is allowed to consider how flexible one is and how costs can be reduced. We would build such a steep roof immediately if the costs were manageable. Quite simple.

Architects take, analyze the surrounding buildings (for the 34er not only the neighboring house is decisive, but also the surrounding buildings), submit a formal preliminary building inquiry

We will probably do it that way, or rather the building authority has indicated that we can coordinate our plans with them even before the preliminary building inquiry and the building application, and that this is also desired. That definitely makes sense.

Then also clarify the parking of cars (how many?) in front of the house.

I have purchased a plot of land including an old house and want to build a new house on it,

Is it about house number 14, where you marked the plot with a yellow frame? How young/old is the house or when was it renovated? Are you sure that you want to tear down a semi-detached house and can weigh the risks that then affect the other house?

I am confused that you then only have to maintain your 2.5 meter setback. The other half is right on the boundary. As I understand it, you would then also have to provide the 2.5 meters for the neighbors. Check the 'Hausanschlusskasten' again and be on the safe side.

I had done that. But I will do it again just to be safe. Thanks for the hint. The answer at the time was that we only have to keep the 2.5 meters, even if the other house is on the boundary or not 2.5 meters away from the boundary, because it’s not our fault. However, the neighbor must also keep 2.5 meters away or build a firewall if he wants to build again on the boundary, provided he demolishes the existing structure.

Is it about house no. 14, where you framed the plot in yellow? How old/new is the house or when was it last renovated? Are you sure you want to demolish a semi-detached house and can weigh the risks that then affect the other house?

Yes, correct. The house is from 17xx. It was last renovated in 1960. Yes, on the plot where house no. 16 (year built: 1990) stands, there used to be the other half of house number 14. Back then, the demolition was also not a problem.

Have you also read and understood Beitrag 11 ?