Building permit with/without building land?

OK. I understand. So I will call the community building department ... Still, I thank you for the information, since I have had no idea about it so far. Maybe I will still get my [Gästehäuschen].

It is a garden plot within a village that is designated as a "settlement".

Are there other houses on neighboring plots?

Maybe I will still get my guest house.

And do you already have a house there? My opinion: if you want to make living rooms for weekend living in the "house" there, you need a building permit. Even for a small storage shed, you need a permit for a certain minimum size.

It is a former timber mill. There are buildings on the site and in a small developed part (60m²) there is already a weekend apartment. On the surrounding properties there are residential houses. We would like to additionally set up a wooden cabin for guests...

It is a former wood factory. There are buildings on the premises and in a small developed part (60m²) there is already an apartment. Residential houses stand on the surrounding properties. We would like to additionally set up a wooden house for guests...

At first glance, this sounds more promising for your project, but it also requires further explanation (in the form of a detailed, more precise description of the property). If I understand correctly, the desired building site lies outside the area potentially designated for development so far (and presumably in the outer area). It is not uncommon with large properties on the edges of settlements that they partly lie in the outer area (whose boundary is also strictly preserved).