Problems with neighbor's encroachment and building authority

Hello everyone,
I specifically registered here because I need some advice.

The following happened: we built in 2013 and at the beginning of 2014 we filled up to a non-permission-required height and supported it with a retaining wall.

Then the neighbor demolished a building in mid-2014 that was built right up to the property boundary and deepened our land by 210 cm over a width of 50 cm, which, among other things, damaged our retaining wall.
He then also retained the land (i.e., his 210 cm deepening) with a retaining wall, but not on his property, rather on ours.

Now the situation is that the neighbor’s retaining wall alone no longer qualifies as permission-free (because it is over 2 meters).
Together with our retaining wall, which stands slightly set back behind the neighbor’s wall, the structure is just over 3 meters high.

In 2017, the neighbor involved the building authority, which ordered us to have the retaining wall approved and to have the boundary measured (the “nice” neighbor had also removed the boundary stones, which made a new survey necessary).

In 2018, despite our warnings to him and the construction company carrying out the work (presumably his own), and a neon yellow glowing boundary marker that was impossible to overlook, he again deepened our property and built another retaining wall on it (this time, so to speak, crossing the boundary as an “extension”).

A building permit now costs around 4,000 euros in total, which we do not want to cover.
Additionally, enormous costs for a structural engineer have now accrued, since we needed to know whether the neighbor’s wall parts could be removed without our retaining wall collapsing.

The current situation is: the neighbor’s walls cannot be torn down without rendering our retaining wall structurally unsound.

The building authority does not consider itself responsible because the neighbor claims he neither excavated nor built over — the building authority has documents on the exact boundary and the original heights; since we filled our property, it is logically not us who deepened and retained our property to the neighbor’s detriment.

In any case, the neighbor has also built a parking lot, a garden shed, and a fence on our property in addition to the aforementioned retaining walls.

To maintain neighborly peace, we then offered the neighbor to have the deepening, including the permission-required structure on our property, approved, and in return, he could use the 21 sqm of land free of charge.

This exceedingly kind and generous offer from us was rejected by him.

The current status is that we have now filed a lawsuit at the regional court for removal and restoration of the natural terrain (which would eliminate the need for a building permit since the original state of the property would be restored).
After the restoration of the terrain, logically, my neighbor would have to retain on his own property.

Since the neighbor and his lawyer continue happily to lie in defense against the lawsuit (claiming the property does not belong to us and that nothing was built over, all of which was already refuted by us in writing in the statement of claim) and no concession can be expected here, I assume that even after a judgment is pronounced, the neighbor will not remove his overbuildings/land deepening.

My question now is (perhaps there are experiences here regarding this):

How do I clarify this with the building authority?
They want to pin the blame on us but somehow also do not want anything to do with this whole theater.

Who is responsible here for the restoration of the natural terrain or alternatively for the building permit?
We, as property owners, or the neighbor as the builder?

Whether a possible compulsory enforcement will be successful is also questionable (by now the guy has at least 5 children).

And an alternative performance at our own expense is financially not possible at the moment (maybe in 5-10 years).

How do I clarify this with the building authority?
Because apparently it is already the case that the building authority can also obligate us as property owners.
I have already spoken with the head of the office, but he unfortunately does not seem very motivated to resolve this. :-/

Does anyone have an idea?
I would like to bring this whole theater to an end as quickly and objectively as possible without having to take legal action against the building authority again (all of this also costs a lot of money, time, and nerves).

Thanks very much in advance for all well-intentioned advice!

Best regards.

First of all: There can and will be no legal advice here. But I am happy to let you know what I think about your case:

If it is true that the neighbor has erected a non-permitted structure on your property, then as owners of the building plot, you are also obliged to legalize this structure (since you did not call the police when he unlawfully built the structure on your land). Therefore, you are also the ones who would have to pay for the demolition of the illegal building by way of substitute performance by the building authority.

I do not know if it was already falsification of documents when he removed the boundary stones – in any case, I would not have allowed him to erect the structure, and also damaging your retaining wall (and not restoring it) is not covered by his right of access; for the demolition of his building, he would have only been allowed to enter your property in consultation with you (and only destroy what is unavoidable, repairable, and restored). From your description, these are all deliberate acts of property damage of the highest order.

What on earth made you watch so calmly through it all?

Hello,

Thank you very much for the kind reply.

The problem was that the boundary markers were overgrown and for years we assumed a different boundary line (everything pointed to that - long story). In any case, the encroachment only came to light with the new survey, which was carried out by us. It can now be proven that the boundary markers were originally there. I should have at least called the police at the second intervention, yes, that was a bit stupid of me. The second time I involved the building authority and my lawyer, but unfortunately no one was really able to help me then. :-(

Thanks again and best regards.

Oh, so it is about restoring the natural terrain so that the neighbor's wall then continues underground (demolition is, as mentioned, not possible because the neighbor's retaining wall also, among other things, supports our retaining wall, so to speak). However, the neighbor then has to provide support on his property.

I do have a claim against the building authority to take action. Just because the neighbor demonstrably lies to the building authority brazenly, they cannot simply come to me out of convenience, can they? Don’t they first have to try to enforce it with the neighbor?