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

Hey
We have had our building permit for an EFM for several months now. However, the start of construction has been delayed.
In the meantime, the desire for a granny flat has increased, and it would also be possible without changing the outer layout. Inside, some additional doors would need to be planned, as well as additional kitchen connections.

Now the question about the new permit. Do we need the entire approval process again, or is there a smaller variant?

Or is it possible without an architect?

Baden-Württemberg....

A second residential unit must be approved.

So, really with complete submission and another 2,000 fee?

Such a subsequent application is certainly sufficient. Just ask the architect and the building authority. It is about a second residential unit. It must comply with the building plan and meet the energy-saving ordinance. Anyway.

Change of the external floor plan possible. Inside, some additional doors would have to be planned and kitchen connections added.

And possibly other walls between the main apartment and the granny flat...

Do you have your own architect? Or is it the one from the general contractor?

In the meantime, the desire for a granny flat has grown and it would also be possible without changing the external floor plan.

What are the dimensions of the changes: a "different" house with only the same external dimensions, or making the children's room separable as a living unit?