Boundary construction garage, windows possible

Can’t you just install a garage door with a window? Then you would also have brightness in the [Butze].

I have browsed a bit in the BayBo.

You did not browse the BayBo, but the law for the implementation of the Civil Code. That is civil law. BayBo is public building law and according to it openings in building enclosure walls are not permitted.

Therefore, windows should basically be possible.

No, not on the boundary. Otherwise, your neighbor could no longer place his garage on the boundary. Glass blocks could be permitted. But they are of no use to you if your neighbor exercises his right to build on the boundary.

That's how it is: definitely not at the limit!

Here in Bavaria it is not permitted, I was told at the building authority.

Hello, I had an approximately 5-hour conversation on Saturday with a very experienced draftsman/structural engineer who has planned/drawn and supervised countless houses. He told me windows are possible, they just have to be fire protection windows F90, and those are very expensive. Who is right now? I also don't read anything to the contrary in the BayBo (and that presumably applies). The fact that the neighbor could theoretically block the window is initially completely irrelevant; it's about whether I am legally allowed to install windows.

very experienced draftsman/structural engineer who has planned/drawn and supervised countless houses.

Who says that? No, definitely not. No window is allowed on the boundary (if that was the question) Anyone who boasts about having planned dozens of houses... because quantity has nothing to do with the regulations. You don't need experience to apply legal texts. At least not here.