Building height of 8.5 m with basement and 2 full floors

You will probably have to conduct the discussion with the house provider with a focus on approval, but technically with the basement provider.

So that means I have to bring both together at least for one appointment at a common table? Or into a conference call? Or just make sure they coordinate among themselves? Or how does that work?

The district administrator will shake his head over this through the municipality and mentally apply "foundation slab" only to houses without basements and replace it here with "OKKD".

He will do that, in case I would pursue legal action (which I still do not intend to do, purely theoretically). What does "OKKD" mean? Top edge of basement ceiling? If he replaces it like that, then everything is as it is now. At least for me. The city would then have a "clean" development plan, which however will no longer benefit anyone, since everything has been built. For that, I do not need to wake the district administrator.

Exactly because of such nonsense the requirement of definiteness was "invented"

And that was exactly what again?

The entrance will be on the existing side by the way. That is north. The living area faces south.

Ah, they really don't make it easy for you either...

: I will reply once more separately to your answer.

"Landrat" referred to the assumption that the ultimately responsible approval authority here is the district, which may be regulated differently depending on the federal state.

"Bestimmtheitsgebot" means that laws and regulations are not allowed to use vague terms. For example, "center of X" or "center of Y," but not "center of Kannstediraussuchen" or "center of Weißichselbernicht." For example, "the height of the manhole cover closest to the property on the entrance side" would be a clear height reference point. Or "top edge of the basement ceiling (or floor slab in non-basement buildings)" would be a "certain" term.

If a development plan specifies a knee wall Drempel, or the wall height also for a flat-roofed house eaves height, this does not harm the validity, however.