Terrace planning for a corner terraced house with a large garden - What to consider?

Even if nothing changes in the calculation, a correction

Taking into account the permissible exceeding of 50% for ancillary installations (§ 19 Abs.4 Baunutzungsverordnung) results in a maximum allowable floor area of 270 m²

No, it is 180 sqm plus an exceeding of up to 90 sqm for garages, parking spaces, and driveways/paths.
The terrace itself is legally an ancillary installation but belongs to the 180 sqm, not to the exceeding area.
Whether the terrace is within the building boundary is indicated by the development plan.

Even if nothing changes in the calculation, a correction

No, it is 180sqm plus an overrun of up to 90sqm for garages, parking spaces, and driveways/paths.
The terrace itself is legally an ancillary structure but belongs to the 180sqm, not to the overrun area.
Whether the terrace is within the building envelope is stated in the development plan.

Can we go through this again properly? I would be very grateful:

So I have now calculated, if I build according to my wish, I would be at 70m2. However, more precisely,
8.5m x 4.20m terrace, so 34m2 at the front,
plus at the bay window 4 times 3m = 12m2, a total of 46m2.

The terrace roof is only supposed to be 7 times 4, so 28m2.

As for the building envelope, there is no specification in the development plan. It says that outside the building envelope it should be landscaped. Since there are no further specifications, according to the building use ordinance, ancillary structures are permitted, i.e., also terraces but without a roof.

Perhaps I should first apply to specify these without connecting the terraces. That is, a building inquiry for a terrace roof 7 by 4, i.e., 28m2, plus the two terraces.

The uncovered terrace counts as an ancillary structure, the covered terrace as a main structure.

That would mean, if I count house, bay window, terrace, the covered one, I am at
House 70m2
Bay window 6m2
Terrace 28m2

Even if I take the building envelope:
at 104m2 divided by 280 = 0.37

And the ancillary structures:
3 parking spaces with access and small terrace
40 the parking spaces and 12m2 the terrace at the bay window without roof

40:12 is 1.85 also still below.

Please note that I used 280 m2 as the total area (building envelope) instead of 450m2 (total plot).

Even if nothing changes about the calculation, a correction

No, it is 180 sqm plus an exceedance of up to 90 sqm for garages, parking spaces, and driveways/paths.
The terrace itself is legally an ancillary structure but belongs to the 180 sqm, not to the exceedance area.
Whether the terrace is within the building envelope is determined by the development plan.

Oh wait, now I understand what you corrected.

Even with 180m2 for the main structure, I would still be well below the limit with a footprint of 450m2 and a terrace of 70m2. So I could still use 90m2 for paths, garden house, etc., of which 40m2 are for parking spaces.

So I can build a 70m2 terrace outside the building envelope at the house.

It is considered an ancillary structure.
The only problem is if I roof it outside the building envelope. In that case, I need a permit for the roofing. Are you still following? That’s correct, right?

Sorry, I didn’t mean to confuse, but above I still assumed the worst case, that only the building envelope is considered as total area, even then it barely works.

If nothing about terraces is stated in the development plan, then the Building Use Ordinance applies and it states that terraces are exempt from approval if I comply with distances, site coverage ratio, etc.…

If nothing about terraces is stated in the development plan, then the building use ordinance applies

What does the state building code say?

Are you still keeping up?

I don’t have to keep up, as concrete numbers and information are completely unknown to me.

What does the state building code say? I don’t have to come along since concrete numbers and information are completely unknown to me.

So my head is boiling. I will submit a building inquiry with all my wishes and have it checked. Now I have read in the development plan, outside the building window "to be landscaped" which does not mean terraces are allowed? Everyone interprets it differently. Then terraces are sometimes considered ancillary structures and sometimes not.. I don’t know what to do anymore...

I believe that this passage "gärterisch gestalten" leads to the fact that I am not allowed to build a terrace after all. Therefore, only the building window was calculated as the significantly smaller area for the plot ratio. Therefore, I also have to obtain a permit for the other terrace. Since I read different things, I include my project in the building inquiry.