separate apartment in basement / requirements

I am currently planning to build a single-family house with a granny flat. The construction site is NRW. The basement was originally intended to be a pure utility basement. However, since underfloor heating is also planned and the clear finished height should be about 2.20–2.30 m anyway, I am currently wondering what effort it would take to integrate a third apartment there. It should not really be used separately, but for KfW it could be interesting. I have to ensure the size of the windows corresponds to 10% of the room size. My question is, how should I interpret the following sentence: "Im Übrigen sind Aufenthaltsräume und Wohnungen in Kellergeschossen nur zulässig, wenn das Gelände vor Außenwänden mit notwendigen Fenstern in einer für die Beleuchtung mit Tageslicht ausreichenden Entfernung und Breite nicht mehr als 0,80 m über dem Fußboden liegt." The terrain is currently about 60 cm below the planned height of the ground floor. Is it also possible to excavate on one side for the corresponding windows in the basement, and how large would this have to be? Is the project somehow practical or am I with the planned height way too low, i.e. the basement too deep in the ground?

Hello,

in the state building code for Baden Württemberg, for example, a clear room height of at least 2.30m is required for living rooms - exceptions in the attic are possible.

What you should rather think about, however, is the required second escape route - you will not get around a corresponding light well with escape ladder or being extinguished at a certain angle.

I would therefore recommend that you contact the responsible building authority and clarify your questions there.

Regards,

Dirk

Hello,

The basement was actually supposed to be purely a utility basement. However, since underfloor heating is also planned and the clear finished height should be around 2.20-2.30 m anyway, I am currently wondering what effort it would take to integrate a third apartment there.

First, you should clarify whether you are allowed to build a 3rd dwelling unit according to the development plan or possibly § 34?

If it is permitted, 2.20 to 2.30 m clear finished height is not enough; the apartment must have at least 2.50 m clear finished height. Connections for kitchen and bathroom must be available, as well as living room windows, a second escape route must be established, and a separate entrance must be present.

It shouldn't really be used separately, but it could be interesting for KFW.

Not a good idea; keyword subsidy fraud

I have to make sure the window size corresponds to 10% of the room size.

No, ⅛ of the floor area.

My question is, how should I interpret the following sentence:
"Otherwise, living rooms and apartments in basement floors are only permitted if the terrain in front of exterior walls with necessary windows lies no more than 0.80 m above the floor height at a distance and width sufficient for daylight lighting."
The terrain is currently about 60cm below the planned height of the ground floor.

So, more than high enough. That means a living room in the basement is allowed.

Is it also possible to excavate on one side for appropriate windows in the basement and how large would this have to be?

The excerpt from the textual stipulations is clear; a granny flat in the basement is not possible for you. Of course, this can be realized via light wells, but for that, an exemption from the development plan would have to be approvable. First ask the building authority whether they are okay with light wells/gradings and, very importantly, whether a 3rd dwelling unit is even allowed.

Best regards from the Rhineland

2.50m clear height? Are you sure? Then our entire house should not have been approved, because we do not have that anywhere (except the upper floor without the attic).

2.50 m clear height? Are you sure? Then our entire house would not have been approved, because we do not have that anywhere (except for the upper floor without the roof pitch).

You are right! "§ 48 Building Regulations NRW – Habitable Rooms (1) Habitable rooms must have a floor area sufficient for their use and a clear height of at least 2.40 m. For habitable rooms in residential buildings with no more than two apartments, for habitable rooms in the attic and basement, and otherwise for individual habitable rooms and parts of habitable rooms, a lower clear height may be permitted if there are no concerns regarding their use. Habitable rooms under a sloping roof must have a sufficient clear height over at least half of their floor area; parts of the room with a clear height of up to 1.50 m are disregarded." 2.40 m would have been the correct answer for NRW. Rhineland regards

Ok, thanks for the info. For BW, to my knowledge, it is 2.30m. At some point, I had checked that in the [Landesbauordnung].