ᐅ Basement extension beyond the designated building area

I am planning to extend my house by adding a basement apartment—essentially building a livable cellar—below the terrace and into the garden (so the garden would be partially underground). Does the building envelope also apply to the basement?

Short and clear answer – is there perhaps any explanation for this? Because – even with (from Meier’s point of view, of course, difficult) objective considerations – who besides me actually suffers any damage from it? The terrace is there anyway, whether there is a basement underneath or not – same goes for the garden...

markusmaybaum schrieb:
short and concise answer

It was also a brief question with limited information.

markusmaybaum schrieb:
is there maybe any reasoning behind it?

In Germany, land use is regulated by planning law, which is primarily defined in the Federal Building Code (Baugesetzbuch) and the Land Use Ordinance (Baunutzungsverordnung). These regulations do not distinguish between above-ground and underground areas when it comes to buildable surface area (§23 Baunutzungsverordnung).

markusmaybaum schrieb:
who – apart from me – is affected negatively by this?

The soil, as it can no longer fulfill its natural functions.

markusmaybaum schrieb:
the terrace is already there anyway

Since you have not yet shared the development plan with the forum, we would have to go through some “if…then” scenarios, which I will spare us for now and simply question the legality of the terrace if it is located outside the building envelope. I have previously commented on this topic here:

Escroda schrieb:
Terraces are a controversial topic

Even if it were permitted there, it makes a big difference whether there is soil underneath or a living space – key issues include lighting, ventilation, emergency escape routes, parking spaces, plot ratio (Grundflächenzahl), and floor area ratio (Geschossflächenzahl).

Note: Regarding my self-quote, I would like to point out the long unknown feature that the small white triangle links to the entire post.

In the course of making our everyday thinking more ecological, I no longer know of any building plans in my immediate area that allow terraces outside the designated building envelope, especially not basement apartments. The purpose of building envelopes is to maintain distance from neighboring properties, so as neither to block their sunlight nor cause nuisance. This naturally also restricts terraces and basement apartments. In sloped terrain, strict building envelopes also implicitly limit excessive excavation or filling. Karsten

Nordlys schrieb:
In the context of the increasing ecological awareness in our everyday thinking, I no longer know of any local development plan that allows terraces outside the building zone

... this should also apply to the buffer strip, just to clarify further

Hmm? Boundary strip? What do you mean?