ᐅ How is the maximum allowable living area calculated?

Hello everyone,

I am currently planning a semi-detached house on a sloped site and have run into a major problem that is causing me a lot of frustration. Maybe someone here can help me understand it better.

Here are the key details:

• Plot size: 217 m² (2337 sq ft), floor area ratio: 0.45 → maximum buildable footprint of 97.65 m² (1051 sq ft).
• No floor space index specified.
• 1 full storey allowed, with a gable roof at 35° pitch (eaves height max. 4.50 m (14.8 ft), ridge height max. 9.00 m (29.5 ft)).
• Currently planned living area: 131 m² (1410 sq ft) (ground floor and attic).
• Balcony: 7.5 m² (81 sq ft); I wanted to make it a bit larger.

My architect strictly refuses to enlarge the balcony, saying that this would exceed the maximum allowable living area. However, he does not explain in detail how this limit on the maximum living area is calculated. There seems to be an absolute limit that, according to him, must not be exceeded. I understand that the ground floor footprint is clearly restricted by the floor area ratio (97.65 m² (1051 sq ft)). But how is the maximum possible living area in the attic calculated? The eaves height, ridge height, and roof pitch naturally limit the usable space—but what is the basis for determining this maximum area? I haven’t received any convincing explanations from my architect on this.

I am currently quite at a loss and would appreciate any help to better understand this or any advice on how to proceed. Thank you very much in advance!

Which construction area is it? Which plot of land?

First of all: 97.65 square meters (1,051 square feet) is the maximum footprint; the living area on the ground floor will of course be smaller. The full storey height usually refers to the living area and is regulated in the state building code. -> This must not be exceeded.

What about the slope? For 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? Try adjusting the cross-section of the slope. And what are your actual requirements?

baulaie89 schrieb:

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

If you don’t want to become your own worst enemy, never plan a single semi-detached house, and especially not on a slope.

baulaie89 schrieb:

Here are the basic details: [...] Here are the development plans (land use template C)

You shouldn’t post links like that here. By the way, there is already a thread for like-minded people about your building area: https://www.hausbau-forum.de/threads/bauherren-im-neubaugebiet-steinriegel-wendlingen-am-neckar.41738/

baulaie89 schrieb:

Maybe someone here can help me understand this better. [...]
My architect strictly refuses to enlarge the balcony because he says it would exceed the maximum allowable living area.
However, he doesn’t explain in detail how this restriction on the maximum living area comes about.

With a 217 sqm (2337 sq ft) plot, a site coverage ratio of 0.45 results in a maximum footprint of 97.65 sqm (1051 sq ft), which on the ground floor corresponds to about 78 sqm (840 sq ft) and a total living area of roughly 117 sqm (1259 sq ft). A terrace is fully included in the footprint calculation. A balcony (on an upper floor) counts only towards the living area. Since the attic is not allowed to be a full storey, its area (including enclosing walls) is limited to two-thirds or three-quarters (depending on the federal state) of the comparable ground floor area, as long as it reaches a ceiling height of 2.30 m (7.5 ft). This also applies to a balcony, so it is counted accordingly. Whether this applies only proportionally here as it usually does in living area calculations can be debated. Your architect can certainly provide you with a detailed calculation for this—it is even required for the building permit application (to prove that the attic is not a full storey). How is your semi-detached neighbor handling this?

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In my opinion, semi-detached houses are only permitted in zone C, but you won't find a 217 m2 (2,328 sq ft) plot there. Actually, such a small plot hardly exists at all.

hanghaus2023 schrieb:

Duplex houses are, in my opinion, only permitted in zone C.

I agree with you, I just read the text.

hanghaus2023 schrieb:

But you won’t find 217 m² (2,327 sq ft) there.

Those figures are not square meters (too similar for that), they must be heights instead.

ypg schrieb:


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

This is the first time I have seen this in a development plan. But of course, it’s good that the maximum building height is included right away.