Neighbor wants to build a semi-detached house with an offset

Yes, it just becomes much more expensive for both, and at the back our corner wall would then probably need a retaining wall or a 2m deep strip foundation, I assume. That spot is the deepest, down to street level, topsoil removed about 1.5m plus or minus.

Does that work? I can't find anything specific for semi-detached houses in the development plan.

I can't find anything specific for semi-detached houses in the development plan.

Landshuter Straße? I don't find any special regulations there.

I would ask the building authority whether there is a binding front building line.

I would ask the building authority whether there is a binding front building line.

Although there are unexplained symbols in the plan excerpt, no building line is visible. As I said, I also don't think the neighbor is specifically intent on winning a medal for stupidity and that only a legal argument would convince him. Therefore, my recommendation is to coax out his reasons and then show him how he can meet them without an own goal/Pyrrhic victory.

Kitchen floor plan is final, cannot be changed.

This is a fundamentally avoidable attitude, and the construction of a temporarily detached semi-detached house is always procedurally dangerous.

I assume that the neighbor is simply taking the opportunity to build a protected terrace.

I assume that the neighbor is simply taking the opportunity to build a covered terrace.

And hopefully nothing more. That was exactly my point.