ᐅ Attic with roof terrace → Full storey calculation

Hello everyone,
I am currently planning the renovation of my parents' house and have a question regarding the calculation of a full story. Upon request, I received an excerpt from the building authority that defines the calculation... but I am not entirely clear on it:

For a full story, the attic must have a clear height of at least 2.3m (7.5 ft) over at least two-thirds of the area of the floor below. How is this affected if a roof terrace is planned? As far as I understand, a roof terrace does not have a clear height... Does it then count as an area above 2.3m (7.5 ft) or below 2.3m (7.5 ft)? In more recent plans I have read that a roof terrace is not taken into account in the calculation... however, the wording "the floor area of the story below" would suggest that the roof terrace should also be included...

The more specific background is that I am not allowed to build another full story, so it would be important for me to know if a full story can be avoided by adding dormers, and at the same time planning a slightly larger roof terrace.

I hope you can help me, and thank you in advance for your attention.

Regards,
SimVo91

I still don’t quite understand why you want to make the roof terrace larger. What do you expect to gain from that? The top floor is still only allowed to have a height of more than 2.30 meters (7.5 feet) on a maximum of two-thirds of the area compared to the floor below. This means, if the floor below the attic is, for example, 80 m² (860 ft²), then on the attic floor you may exceed a clear height of 2.30 meters (7.5 feet) on a maximum of 53 m² (570 ft²) of the floor area. An absolutely exaggerated roof terrace of 100 m² (1,076 ft²) won’t help you in this case.

It is also possible that I am misinterpreting everything and understanding it in a way that suits me... My thought is, if, as in your example, the lower floor has 80m² (860 sq ft) and there is a 27m² (290 sq ft) roof terrace, can the remaining part of the floor (that is, the 53m² (570 sq ft)) have a full ceiling height of 2.30m (7.5 ft) or more?

I mean not a detached roof terrace (or whatever it’s called...), but something like that, just with the rest of the floor at full floor height...

Simply define perimeter walls. Focus on clear ceiling height and leave out the roof terrace for now.

This is actually how it should be! In the end, it’s simply about the fact that at most two-thirds of the attic floor have the minimum clear ceiling height. The roof terrace does not count towards this, so you could design the remaining one-third as a roof terrace or have a clear ceiling height of less than 2.30m (7 ft 7 in) in that area.

The only restriction for the attic floor not to be considered a full story is that you have a clear ceiling height of 2.30m (7 ft 7 in) on no more than two-thirds of the floor area.

ypg schrieb:

Just define what you mean by exterior walls.

Exterior walls are the outside walls of the house... however, in the extract they are only used as the basis for calculating the floor area ratio, which is not really relevant for me (floor area ratio of 0.7 and a plot of 1016m² (10935 sq ft)... current footprint about 140m² (1507 sq ft) with one full story... so I still have a lot of room left in terms of floor area).

ypg schrieb:

Focus on clear ceiling height and leave out the roof terrace for now.

I’ve actually already read up well on clear ceiling height, etc. I don’t really understand why I should leave out the roof terrace, since I definitely want it and only want to know if it is included in the area with a ceiling height lower than 2.3m (7.5 ft).