Build a house with a knee wall 75cm high or two full stories? Your opinion?

I would normally always prefer the pitched roof with knee wall, but the 75 cm specification is simply too little. We have 1.14 m here, which is quite nice and enough for a bed and such against the wall. Upstairs we have a sauna where you can sit comfortably under the slope.

Under 1 m is totally impractical.

I had my children's and youth room in a house without a knee wall. Built-in closets up to one meter high were partitioned off by the carpenter, with closets behind them. With a 45-degree roof pitch, I see absolutely no problem in going even further, for example by creating a storage room behind a wardrobe in the bedroom. And in my opinion, a house with a low knee wall also looks much more pleasing. Personally, I am not a fan of having my terrace in front of a straight, high house wall and feeling overwhelmed by the bulk. I had that, and I never want it again.

Does that mean that the development plan contains a formal error and would therefore be null and void?

One could have that legally reviewed. The city planners will probably try to excuse themselves with the transitional provisions, which refer to the earlier definition of a full floor in the BayBO of 1998. In my opinion, however, that is not a proper way of working.

The concept of a full storey was abolished in Bavaria eleven years ago.

And does that reduce legal certainty? - does that now make all storeys countable storeys, or must one now generally avoid residential standing height in the basement and the sloping roof?

And thus reduces legal certainty?

I think so! A term definition from a legal norm (BayBO) is deleted with the expectation that it will be included in another legal norm (Baunutzungsverordnung). But it is not. Nevertheless, the term continues to be used. Now practitioners can go on a treasure hunt, from the development plan to the Baunutzungsverordnung, from there to the current state building code, from there to the old state building code, and back to the development plan.

does this now make all floors countable floors, or must one now generally avoid residential ceiling height in the basement and in the pitched roof?

... and exactly these questions are interpreted by each participant in their own way, so that in the end courts have to be involved again, simply because the legislators do not do their homework properly. Sorry, I’m digressing. It is probably unimportant here anyway because the plan authors assume the old definition of a full floor anyway and two full floors are permitted here, regardless of whether with or without slopes and the dimensions do not allow an attic with debatable proportions to arise.

The term is still used, though.

So you mean: only the definition was "abolished"?
:-(