How is the maximum allowable living area calculated?

Hello everyone,

I am currently planning a semi-detached house on a hillside and am encountering a major problem that is driving me crazy. Perhaps one of you can help me understand it better.

Here are the key data:

[*]Plot area: 217 m², floor area ratio: 0.45 → maximum buildable area of 97.65 m².
[*]No floor space index specified.
[*]1 full storey allowed, plus a gable roof with a 35° pitch (eaves height max. 4.50 m, ridge height max. 9.00 m).
[*]Currently planned living area: 131 m² (ground floor and attic).
[*]Balcony: 7.5 m²; I wanted to enlarge it slightly.

My architect strictly refuses to enlarge the balcony because he says we would exceed the maximum allowable living area. However, he does not explain in detail how this limit for the maximum possible living area is derived. There seems to be an absolute limit that, according to him, must not be exceeded. I understand that the ground floor area is clearly limited by the floor area ratio (97.65 m²). But how is the maximum possible living area in the attic calculated? Of course, the eaves height, ridge height, and roof pitch set limits on the area – but what is the basis on which this maximum area is determined? I do not receive any comprehensible answers from my architect on this.

I currently feel helpless and would appreciate it if someone could help me understand it better or give me pointers on how to proceed here. Thank you in advance!

Which construction area is it? Which plot?

In advance: 97.65 is the maximum floor area, the living area on the ground floor is of course smaller.
The full story status usually refers to the living area and is anchored in the state building code. ->
That is to be undercut.

What about the slope?
With a house, you have to think in 3D, especially with a slope.
But you also have to trust the architect. What is the purpose of the balcony?
Just place the section of the slope. And what are your actual needs?

I am currently planning a semi-detached house on a hillside

If you don’t want to become your own worst enemy, then never plan a single semi-detached house, and on a hillside even less so.

Here are the key data: [...] Here are the development plans (usage template C)

You shouldn’t link such things here. By the way, there is already a like-minded thread for your building area:

Maybe someone of you can help me understand it better. [...]
My architect strictly rejects enlarging the balcony because he says we would exceed the maximum allowable living area.
However, he does not explain in detail how this limitation of the maximum possible living area comes about.

So from 217 sqm plot you get a floor area ratio of 0.45, meaning a maximum of 97.65 sqm floor area, which will lead to about 78 sqm on the ground floor and about 117 sqm total living area. A terrace is fully included in this floor area. A balcony (i.e. on the upper floor) is only included in the living area. Since the attic floor may not become a full storey, its area (including enclosing walls) is limited so that it may only amount to 2/3 or 3/4 (depending on the federal state) of the comparable area of the ground floor, as long as it reaches a height of 2.30 m. This applies to a balcony as well, so it is counted accordingly. Whether this generally only applies partially here as in the living area calculation can be debated. Your architect can definitely calculate this for you; in fact, he must do so for the building application (when proving the attic is not a full story). How does your semi-detached neighbor handle this?

A semi-detached house is in my opinion only permitted in C, but you won't find 217 m2 there. Actually, there is no such small plot of land at all.

Duplex is, in my opinion, only permitted in C

I agree with you, I just read the text.

but you won’t find 217 m2 there.

The numbers are not square meters (they are too equal for that) but must be heights?

The numbers are not square meters (they are too even for that) but must be heights?

This is the first time I see that in a development plan. But of course, it's good that the BZH is written in right away.