Building permit for a single-family house granted, is an additional granny flat still possible?

Okay 2.3 then I have our finished height of 2.4m in the [Einliegerwohnung] in mind.

What are the legal regulations for a granny flat? Or is it handled differently here? The architect and the building authority did not criticize anything.

I have a minimum room height of 2.65 m everywhere. Heating is readable. Ventilation system has not been decided yet and no one cared. Enough light? There are proper windows and terrace elements, just normal.

Nobody cared because you probably fulfill everything!

But with the central controlled residential ventilation, you have to be careful.

But don’t worry, at the latest when you want a 2 kfw credit card for it, someone will take a closer look.

We have "halbiert" the basement and had planned a kind of party room. Therefore, the layout would practically already be like a one-room apartment....

But back to the approval. Is there a smaller version of the approval or only the same version as for the entire house... with folder from the architect and 2200 euro fees?

I am now responding from NRW in the expectation that there are similar regulations in BW. Maybe try using a search engine or follow Yvonne’s (ypg) advice tomorrow.

with folder from the architect

At least the floor plan in the basement changes, possibly also one or the other elevation and the section. The drawings must be signed by the person authorized to submit building applications. Whether they create a folder for this, I do not know.

2200 Euro fees?

AVerwGebO
2.5.2.3 Decision on the granting of approval for intended changes to approved building documents
a) depending on the extent of the deviations in relation to the entire construction project
Fee: up to the amount of the fee according to tariff items 2.4.1, 2.4.2, 2.4.3 or 2.4.4
b) if the fee cannot be determined according to letter a)
Fee: Euro 50 to 250

The fees depend on the effort required to examine the regulations affected by the change. Since nothing changes on the outside, the site plan, separation distances, border setbacks, building limits, floor space index, ..., do not have to be reviewed again. Whether the floor area ratio changes depends on the development plan. Overall, however, the fees should be significantly lower.

Maybe a local person will still respond.