Close the gap between the neighbor's house and our house

How was the house supposed to connect to the neighboring house according to the plan? SO surely not? If not, it would be noticed early during construction that it doesn't fit. So what does the construction company suggest?

Why don't you install a mini roof there? Preferably wood attached to the walls as high as possible, corrugated roofing on top, properly connected and sealed at the sides and back, with a slope towards the front for drainage. Possibly build on the neighbor's property, if accessible?

Why did the gap arise in the first place? How did your planner plan the transition?

There aren't many suggestions for this. Basically, we need to make sure the gaps here are closed. That's why I'm looking for ideas.

Why don't you put in a mini roof there? As high up as possible, wood on the walls, corrugated roofing on top, properly connected and sealed on the sides and back, with a slope to the front, then drain.
Structure possibly from the neighbor’s things, if accessible?

I also thought of something like that, but I think cutting corrugated roofing to the right size and making sure it fits on all sides won't be that easy. That's why the idea with Styrodur, as it can be easily cut and sanded, etc.

Of course, the fundamental question is: Who planned it that way? But well, that only helps to a limited extent in terms of finding a solution.

The question now is, what would your neighbor be willing to agree to? Of course, the gap should be sealed; for that, one could possibly also install/form a gutter. However, it must then be sealed tightly both to your wall and to the neighbor's roof. That way, the area would at least be kept dry. At the front, one could also install a closing sheet metal, and whether to fill the gap itself with insulation is certainly something to consider.

But what does the planner fundamentally say about the whole issue?

The plot situation is unfortunately not the easiest here. It is not an ordinary plot. As described, we have to take care of it.

That would also be an idea. However, it will be very difficult on the other side because the gap narrows in a wedge shape and closes at the back. Then there would be a gap behind the gutter again.

So using Styrodur is not an option at all?

Regards