Undercutting the boundary distance of 3 m

Ask your publicly appointed surveyor if he still has all his marbles to document 2.98m in a 70s cadastre.

What is the usual further procedure?

In NRW nothing would happen.

2) Are there possibly "construction tolerances" within which deviations are accepted?

If it really concerns boundaries from the seventies, the 2cm are clearly below the error limit – hence my introductory sentence. To avoid exactly such questions, it is common to round to building regulation minimum distances within the permissible error limits.

3) How could the grievance – if necessary – be remedied?

If coordinate cadastres exist and ’s suggestion doesn’t work, meaning even an expert commissioned by the neighbor, which will cost around 2k€, also always comes to 2.98m, your neighbor can claim compensation. Court costs 3k, compensation 200€. In short: relax!

If the documents are already on their way anyway, then just ask the office and not us. What worse could happen? You don’t want to hear our lay opinion anyway....

The intention was to benefit from actual experiences (personal or professional) on the same issue instead of frightening the building authority or possibly stirring up a hornet’s nest. Nothing more. Especially regarding question 1), that is, what exactly will happen next (e.g., the building authority contacts me and reports the "violation" or the affected neighbor is written to, etc.).

Best regards

The intention was to benefit from actual experiences (personal or professional) regarding the same issue

Well, Saarland is small and in other federal states it is not common for the surveyor to forward the building survey to the building authority. Where is this standard anchored (legal basis)? §78 (6) State Building Code is only a discretionary provision and the Surveying Act refers to the possibility of a legal ordinance. Does it exist?

to wake sleeping dogs

Regarding my proposal

Ask your publicly appointed surveyor

do you have nothing to say? The dog is already awake. And you paid him.

Nothing more.

... contradicts

I had explicitly asked for profound answers

what exactly will happen next

... I always wonder as well. That’s why I was just at the city library. Unfortunately, the crystal ball is already on loan and there is a very long waiting list, so no binding short-term answers are to be expected.

The intention was to benefit from actual experiences (personal or professional) regarding the same issue instead of making the building authority nervous or possibly waking sleeping dogs. Nothing more. Especially regarding question 1), that is, what exactly will happen next (e.g., the building authority contacts me and points out the "violation" or the affected neighbor is contacted, etc.).

Best regards

Profound answer: woof woof, you have awakened the dogs!! One asks such questions beforehand and then sends the documents away! You are now at the mercy of the species called civil servant. If he acts strictly according to the regulations: dismantling!!!

Unless intent or gross negligence is involved, § 912 Baugesetzbuch applies

As long as neither intent nor gross negligence is involved, § 912 of the Building Code applies

Of course, only in the case of encroachment. Sorry, obviously read inaccurately.

Don’t drive yourself crazy, no one in this field cares about that. Rounding is not done only by merchants.