We have attached our semi-detached house in Fulda (Hessen) to an already existing, completed semi-detached house. We are currently at the shell construction stage and the windows are supposed to arrive in 3 weeks. Until now, our plot was undeveloped.
Our soon-to-be neighbor has approached us, saying he would like to put a fence between the two semi-detached houses and has already spoken with the local garden landscaper. He intends to fence his entire property and wants to start promptly so that the garden can be used in summer.
[ / ] That's why we already had L-walls installed during the earthworks. The privacy screen should be mounted on them. And later simply a hedge. That would not have involved or limited the neighbors.
[ / ] Honestly, I don’t believe he will accept anything other than the fence he wants anyway on the other 3 sides.
That you are not yet ready in your mind (given your comparatively recent building status) for the chapter "enclosure" is no free pass for feeling annoyed by his absolutely legitimate wishes. If I were him, I would also speak in neighborly communication in normal everyday German about a "fence" instead of the neutral but legally sounding term enclosure. I do not see any exclusion or rejection of a hedge in that, and your assumption of his inflexibility in imagining a neighborly boundary determination only in the same design as the surrounding fencing is something he certainly does not deserve. On the contrary: you yourself say he spoke about the project with a garden landscaper (so not a fence builder, but a contractor more suitable for plant-based spatial structuring).
Put yourself in his position once: spring is approaching, and as is well known, summer is not far behind. Would it be comfortable for you to imagine the neighbor’s child and dog – or more precisely: that their frame of reference cannot do anything with a virtual boundary line on a site plan – could pose dangers to the integrity of your flower meadow?
Would you want to postpone your move into the new house including the step "perception of the gardening season" just because the neighbor is not yet ready and his half of the property is still in the stage of a "military training ground"?
What L-walls have to do with the story is not clear to me: is there a terrain difference between the two halves, and who would be the upper layer (and responsible for drainage)?
Tell your neighbor that you find a hedge as the boundary enclosure more sympathetic. If I were in his place and asked my beloved lady whether she would insist on a color coordination with the fence on the other sides in this case, she would surely burst out laughing. Maybe his wife is different and wants the fence in dark green – not your problem. Arrange with the garden landscaper to pay your half of the hedge in 12 monthly installments, surely a fair solution can be found. The day of full payment can then be celebrated together with a barbecue. The beer spilled while tapping will then fertilize your lawn. This is how virtual problems are solved easily!