Roof design / Use of 2nd floor mandatory with 2 full floors

That's why I said maybe.

I see it differently:

That is your prerogative ... the regulations regarding when a floor counts as a full story (there are only rudimentary differences between the federal states) do not play a role in this case. If the Roman numeral II is in a circle, a full and not a _calculated_ two-story construction must be erected. And that is the only thing the OP's information is about ... so far.

Strange, until now I had always been told that I can still work with a knee wall. I'll take that as a point to discuss with the architect. If full stories are really mandatory, it is probably best to keep the pitch at 30° so that the roof does not become unnecessarily high. Still, I don't see a problem with partially opening the roof.

The following is stated as a table in the development plan regarding the total height, measured from the ground floor floor level to the intersection of the exterior wall with the roof:

Number of full stories Building height [m]
I 3.5m
II 6.2m

The following table is given in the development plan regarding the total height, measured from the ground floor floor level to the intersection of the exterior wall and the roof: Number of full storeys Building height [m] I 3.5m II 6.2m

I hardly believe that a state building code applies two different full storey standards at the same time: what is a full storey according to the building code is also one according to the development plan. Suddenly counting only storeys without roof slopes, I see nowhere written. The circling of the number of storeys only means that it is specified here as a requirement, not as an option. The circling does not prescribe a specific way to achieve full storey status.

However, where the number of storeys "II" is prescribed, I do not see simultaneously a choice between one and two storeys – does the development plan also include parcels with a circled "I"? Otherwise, this table makes little sense.

The mentioned height reference is virtually a kind of eaves height, only not measured at the gutter but at the house wall. 6.2 m are sufficient here in any case for a knee wall or even a "full storey à la Iktinos."

I calculated an example with a 180 cm knee wall and 30° roof pitch (gable roof). With a hip roof, the calculation would be slightly more complex. At 45°, even 2 m building depth would be sufficient to create such a full storey.

In my opinion, an opening of the roof underside with (unfortunately not permitted here) 20° roof pitch across all rooms is conceivable without visually "pointing" small rooms. At 30°, I would exclude some rooms from this, and at 45°, in my opinion, it almost suggests inserting sleeping galleries in the children's rooms.

Yes, there are also parcels with an I, but not circled.

Yes, there are also parcels with an I, but not circled.

This is logical in the sense that with only one full floor, the "maximum number" of floors is automatically reached as soon as you build at all. In theory, you could also place a single story with knee wall there, but below that (since basements do not count) there would be no further full floor on whose floor area the height proportions could be based – thus it would "never be" a full floor. You could embed a floor in such a way that you have a basement with knee wall and ceiling top edge less than 1.4 m above ground level. But nobody wants to build such nonsense just because it could theoretically meet the development plan. Therefore, one can safely omit the circle around the "I" here ;-)