Recommendation for terrace partition for a semi-detached house wanted

If he doesn’t overdo it with the back support for the curbs, then you can easily install a WPC fence later. Just leave 20-30 cm of space between the terraces. Otherwise, you can simply knock off the support at the appropriate spots to set posts in concrete. Ideally, you already know where the posts will be placed now, and he doesn’t put any back support there. With a 1m concrete curb, you still have 70-80 cm with support, which is absolutely sufficient. Visually, a wall looks best, but it also costs much more than a fence. In my opinion, the warming of the wall can be neglected. At 30 degrees, a WPC fence also gets warm. I’ve also never heard of anyone considering thermal protection for a partition wall.

Besides privacy, soundproofing would also be important to me, so that both sides don't always have to whisper. Of course, this also depends on the local circumstances, but a single-layer solution provides little protection. Maybe you could jointly plant a dense hedge or add one; furthermore, there are various solutions even with , Mineralwolle, cork, and other materials to reduce this noise. I simply find it unpleasant for both sides when you can hear every word the other person says, and vice versa. Of course, you will always hear the neighbors at this close proximity, but especially on the terrace, I want to be able to have a somewhat "free" conversation.

That was also my thought. Therefore, the wall is probably the best solution, right? I also see the problem with WPC due to the southwest orientation of the garden, that it will discolor sooner or later from UV light. Or is that negligible?

A nice wall also makes sense and each side can then plant as they wish or take other measures for sound insulation. Ultimately, you should find a joint solution if possible.

I also see the problem with WPC due to the southwest orientation of the garden, that it discolors sooner or later because of UV light.

WPC discolors less than wood but has sound insulation like a wooden board wall. In terms of sound insulation, a solid wall is the best, and leave no gap under the roof at the top. If your neighbor laughs loudly, it can get annoying over time.

WPC discolors less than wood but has sound insulation like a plank wall. In terms of sound insulation, a solid wall is the best, and do not leave any gaps at the top under the roof. If your neighbor laughs loudly, it can be annoying over time

What do you mean by “do not leave any gaps at the top”? I'm at a loss right now.