Attic expansion: Definition of full floor and dormer width up to the neighbor

Hello everyone,

the planning of my attic conversion is currently stalling a bit. I am overwhelmed by the flood of information from the architect, the building authority, and the craftsmen, so I need your help to determine what is really possible now.

The house is an end-of-terrace house and it is located in NRW. I want to install as large new dormers as possible at the front and back.

Question 1 about the definition of full stories:
The building authority is against the current plan because a full story would arise. However, the architect says it fits mathematically since some ceilings are low enough. If I want to calculate it myself, I look at the building regulations and it says:

Building Code NRW 2018:
Full stories are above-ground floors that have a clear height of at least 2.30 m. A floor is only a full story if it has the height mentioned in sentence 1 over more than three quarters of the floor area of the floor beneath it.

The clear height is currently 2.10m because the purlins are low. Only in the new dormers is the clear height raised to over 2.3m. For the calculation of whether it becomes a full story, do really only the areas of the new dormers count?? Otherwise, one could trick everywhere, for example by partially lowering ceilings.

Question 2: Dormer width
Am I allowed to build a dormer over more than half the width of the house? Unfortunately, I can't find anything about this.

[U]Question 3: Distance from roof dormer to neighbor[/U]
Can I build one of the dormers up to the common gable wall of the neighbor, provided he gives me his consent?
I think I read that dormers no longer trigger setback distances.
The neighbor is open to my project but wants to avoid a building encumbrance (Baulast).

(On the free side of the house without neighbors, I do not have to build up to the gable.)

I think the three questions cover the most urgent issues. Regardless of the answers, my current concern is to be able to make a decision about which variant of the attic conversion I can pursue further: rather the large dormer up to the neighbor, or as a fallback a version with about 2m distance to the neighbor.

Thank you very much and best regards
Tassimat

Regarding the first question: To my knowledge, the question of what constitutes a full storey and what does not is not determined by the most current building code, but by the building code that was in effect at the time the development plan was issued. (However, this should be checked, as I am not 100% sure that this information is correct). Regarding the height: Rooms that have a clear height of only 2.10 m are not permissible as habitable rooms. The requirements for habitable rooms are specified in §46 of the NRW building code. Regarding the second question: How wide dormers can be designed is usually determined by the development plan. In our development plan, 50% is explicitly stated as the maximum dimension. Otherwise, we could have also built our dormers wider.

A development plan is not known to me. All the houses on the street were built at the same time in the 60s, all houses are identical. Over the decades, however, some variations with new dormers and smaller extensions have been added.

The living spaces with the dormers are half 2.10m high and only the rest in the dormer area is higher. The rafters run right through there. But this has been done this way for all the neighbors as well and is used as living space everywhere.

Shouldn't your architect assess that and show you the correct and feasible way? That's what he gets paid for.

I mean otherwise you could cheat everywhere by, for example, partially removing ceilings.

Yes, you could. Whether the approval authority accepts a construction that obviously only serves to circumvent legal norms in the calculation approach is questionable. And then you end up in court again and wait a few years for a decision.

Am I allowed to build a dormer over more than half the width of the house?

Yes.

Can I build one of the dormers up to the common gable wall of the neighbor, provided he gives me his consent?

Yes. I even claim that his consent is not required.

I think I read that dormers no longer trigger setback areas.

That has been the case in NRW since 01.01.2019.

According to my knowledge, the question of what counts as a full storey and what does not is not determined by the current building code, but by the building code that was in effect when the development plan was issued.

Correct.

I am not aware of a development plan.

Then check whether your knowledge corresponds to the facts. Without a development plan, precise calculations regarding the full storey are not necessary anyway. Quotation from a judgment of the Federal Administrative Court (decision of 21.06.1996, Ref.: BVerwG 4 B 84/96):
In this respect, it also applies to the insertion with regard to the number of full storeys that the externally perceptible appearance of the building in relation to its surrounding development and not the result of complicated calculations is decisive.
In the unplanned inner area (§34 Building Code) the architect is required to include an extensive photographic documentation of the neighboring buildings with the building application to prove that comparable development already exists in the immediate vicinity.

Thanks in advance, the answers help.

Shouldn't your architect assess that and show you the correct and feasible way? That's what he gets paid for.

Unfortunately, not every architect is all-knowing. I don't want to take that negatively against him. Overall, I am satisfied with his work.

I just spoke with him on the phone again. He said we definitely need a building encumbrance, since the dormer is very wide up to the neighbor and no longer counts as a subordinate roof element. Unfortunately, he couldn't tell me offhand where that is stated. He may be right, but if not, then I could build the dormer according to my wishes. Unfortunately, that's what I'm hoping for.

What I forgot to mention is that we have a shared gable wall. That wouldn't be a problem, right?