Neighbor wants to raise the house higher!! What to do?

Hello,

I urgently need some advice.
We own a building plot in a new development area.
Our plot has a slight slope of about 2 m over 45 m.
The neighbor's slope is somewhat steeper, though. He has now asked us if we would agree to him raising his house by about 50-100 cm (filling). Without our consent, he will not receive the building permit. How does this work here? Who has to compensate for the increase and who is responsible for any potential future damages (cracks in the house, etc.)? .. We will only start building in about 2 years, and I am afraid that if we build, damages may occur for which we might be liable.

Does anyone know how we should best decide?

Are you building directly next to each other - you mentioned something about 45m? Without knowing for sure, I am fairly certain that he has to ensure that neither his property drains onto yours nor slips onto it. How is that supposed to work? Most houses here stick out of the ground - those with a basement usually by about a meter. Will you then have a "step" from his entire property down to yours? Tell him that you need some time to think and that you want to first clarify how this affects your planning. Don't let yourself be pressured - but don't totally ruin things with him right at the beginning either.

By the 45 m I mean our plot width. I just wanted to express that the slope is not that steep^^. It’s about our immediate neighbor. The distance between our houses will be about 7 m later.
Basically, I have no objection to him making his house taller, since we will definitely start building later and we don’t want to get on his bad side. I just have concerns about the consequences this will have for us afterward. For us, this only results in disadvantages.
We had already considered giving him our approval but recording in writing that he has to take care of the insurance and that we cannot be held liable for any damages that may occur.

Is your house planning already set? We have a quite similar situation (except that both our houses are already built) and besides the slope stabilization, you should also think about whether there are any disadvantages for you in terms of lighting or views. The question is also how your neighbor wants to secure the resulting slope towards you? L-shaped stones, natural stones, terraced or something completely different (so that you don’t end up always looking at an ugly concrete wall from your windows).

The lighting fits. For our neighbor, only the guest bathroom is actually planned (but it has a window on the other side) and the back wall of the living room, and since we are extending our house further back, that fits and the view also goes to the back. We have no problems with this. We really would "only" have the problem with the wastewater and the hazards during our construction. Who had to bear the costs for the safeguards in your case?

Since we remained at the original ground level and the neighbor (who built after us) made the elevation, they have had to bear the entire cost of the filling, the retaining, and the water management, or still have to bear it. However, this also means we have no influence on how, for example, the retaining of the filling will look, i.e., it could be that we do not like its appearance at all. Furthermore, we have no guarantee that the retaining of the filling and the water management were carried out correctly; we simply have to trust that they were. And if the wall collapses, the neighbor will bear the costs for the damages incurred (let's hope this never happens).