Register a building burden retroactively on your own property?

How wide is the plot? With easements, you would have to keep a distance of 3 meters each time (this mainly concerns the side to 38).

The plot is approximately 13 meters wide but narrows to 11 meters towards the back (where the construction is planned).

It's really a tricky situation! An on-site appointment can help, but it can also lead to the office checking how the windows look.

But without addressing the issue of the windows, the office will probably not be persuaded to allow building further back. It's not entirely unproblematic, so I would probably seek advice from an architect/lawyer with the appropriate expertise to explore possibilities.

I would think carefully about the [Baulast]! Otherwise, you might be jeopardizing something with your construction.

Wow, that would have been a case for our construction law lectures.

Can you post a larger section of the surrounding development here? Something in the radius of 500m to 1km??

Fundamental question 1: Are openings (windows) allowed in fire walls (walls without the required distance area --> boundary walls) in Hessen? Or were they ever allowed in the distant past? You would have to find out where the legal basis for this is. In BaWü it would be LBOAVO (implementation ordinance § 7 para. 8). And then it further depends on whether your neighbors' windows are fixed glazing or can be opened.

Fundamental question 2: what is the "immediate surroundings," as it is nicely called in § 34 Baugesetzbuch. Your building authority has interpreted this very, very narrowly, although even here there is not a 100% exactly identical structure of the surrounding development. (See house number 38)

In general: What someone else has received an exemption for, you are also entitled to. Only no exemption was definitely granted, since there is no development plan with any stipulations.
Regarding the factual element of "fitting in," a lawyer once told me: One day the judge has had a great breakfast in the morning, then it fits in. The next day, it doesn’t again. That is why we now have to gather arguments about what counts as surrounding development and from this it follows how exactly the previous building style has been complied with or not.

which are not approved

And is that certain? Are there no neighborly agreements or even land register encumbrances? When were the houses built? When were these windows installed?

According to the written statement from the building authority

How did that come about? Who requested what and in what form?

According to the previous information, the opinion of the building authority is more than questionable.

Everything was approved like that

Of course, the approval has expired and is therefore no longer worth much. However, with regard to the location of the house, it is a matter of planning law, and not much has changed in the last 30 years, so this approval sets higher standards for the authority’s rejecting arguments than I can read here.

I was told not to even try to submit an application since it would never be approved.

Yes, the deterrence policy popular in the 80s is now experiencing a renaissance.

an excerpt from the building authority’s response

What was the question?

The defining development on the south side of the street is a semi-detached construction on the east side

That is already incorrect. The eastern neighbor built on the western boundary, the western neighbor his rear house, which I assume is a residential building due to the house number, directly on both boundaries.

House number 38 is the exception.

Does it say 38? Then you can see how carefully they work there.

Possible solution: The eastern neighbor applies for a retroactive legalization of his windows. For this, a building encumbrance entry is necessary. Your experienced planner prepares a detailed environmental analysis including photo documentation, designs your house as desired under consideration of the legitimate integration criteria (e.g. wall and building height, building cubature) and submits a building inquiry with references to the previous building permit and unchanged planning law. This forces the authority to issue a legally binding decision, which is usually more considered than a telephone opinion. Should a rejection still be issued, there are written and legally assessable grounds for challenge.

And is that certain? There are no neighborhood agreements or even land register securities? When were the houses built? When were these windows installed?

As far as I know, there used to be glass blocks there, which were replaced by fire protection windows during renovation (except for the small bathroom window with the grate). I don’t yet know whether the neighbor has a permit for this. At that time, only my father gave the verbal okay.
The lady from the building authority checked whether something was entered in the land register for our property, which was not the case, so she assumed that these windows are not approved.

How did that come about? Who requested what and in what form?

I had asked planning law questions by email, since a visit is currently not possible due to Corona.
I wanted to avoid unnecessary back and forth for the later planning and know a few basic things beforehand.
We were not aware that the windows would become a problem, as we did not think that a rollback would be an issue due to the already existing old approval.

According to the current information, the building authority’s opinion is more than questionable.

I see it the same way; I simply suspect that the office only answered the questions very roughly so that they are on the safe side. It may look completely different when it comes to the preliminary building application. (Who knows)

The approval is, of course, expired and therefore not worth much anymore. However, due to the location of the house it concerns planning law, and this has not changed much in the last 30 years, so this approval places higher demands on the authority’s reasons for refusal than I can read here.

Correct, the approval is expired, but it is proof that it apparently was not a problem at one time. However, I am missing solid reasons here why this should no longer be possible now other than “in the past they did not check as thoroughly as they do today.”

Does it say 38 there? Then you can see how carefully they work there.

Indeed, 38 was in the email...

Possible solution: The eastern neighbor applies for a subsequent legalization of his windows. For this, a building encumbrance entry is necessary. Your experienced planner prepares a comprehensive environmental analysis including photo documentation, plans your house as desired while considering the legitimate integration criteria (e.g., wall and building height, building volume) and submits a preliminary building application with reference to the earlier building permit and unchanged planning law. This forces the authority to issue a legally binding decision, which is usually more considered than a telephone enquiry. If a rejection still comes out, there are written and legally assessable grounds for appeal.

I like the idea, thank you.