Expansion joint between 2 terraced houses - Responsibility according to DIN standard?

I have a nice horror novel for you, namely the story of @goalkeeper:

I always have to serve as an example only for the negative cases… no one praises my GÜ and the only eight months of trouble-free construction time. :rolleyes:;)

How now, do both have to pay or just the person doing the extension? You contradict yourself. I say both have to pay.

I wouldn't call reality a contradiction just because it doesn't always follow the pure doctrine. Legally, I see the person doing the extension as responsible - but also helpful to contribute financially so that they don't just proceed as cheaply as absolutely necessary.

I always have to stand in as an example only for the negative ones… no one praises my GÜ and the just eight months of trouble-free construction time. :rolleyes;)

Praise for eight months of trouble-free construction time especially to

I always have to serve as an example for the negative cases... no one praises my GÜ and the mere eight months of problem-free construction time.

You are right! - Your GÜ is almost as fine a guy as your neighbor, and your mayor serves as an excellent bad example :)

Detached houses are practically also terraced houses. Nowadays, in theory, one can remove an existing mid-terrace house without the other walls suffering any loss. It seems to me that it is basically an overall project, but where everyone builds for themselves?! A joint solution, i.e., division of the task "closure," would be the legally most obvious. However, I do not know. It should also be closed in the neighbor's interest - moisture and animals can accumulate there, causing rot on his wooden house.

I can contribute that my former neighbors once built a semi-detached house. The other half, for reasons, was initially not built, and after five years at least the common wall was insulated at the expense of the semi-detached house owner. A year later, the other plot was finally sold again, and the semi-detached house builder had to remove the existing insulation and subsequently carry out (or have carried out) the sealing of the joint. However, there was no discussion about this at all. It therefore does not seem necessarily unusual that the party responsible bears this cost.