… a) All bathrooms/kitchens are planned on top of each other to keep the water installation simple (and thus ultimately reduce costs). The idea behind the shaft was simply the following: the space requirement is about 2 sqm or so, the costs should be manageable since only the shell construction becomes slightly larger. No additional expensive wall surfaces or the like are incurred. The advantage is maximum ease of maintenance with manageable effort...
Of course, you save money if you thoughtfully combine drains. That’s why bathrooms are often stacked, but mainly to get the toilet drain centrally and cost-effectively out of the house without many bends. With all other pipes, you don’t save anything where it’s worth creating a corset for a reasonable floor plan. I think a lot of knowledge from parents or other older generations is still in there [emoji6]
Consequently, this shaft doesn’t have to exist either. It’s smart to have a supply shaft for all kinds of pipes. It can be the size of a chimney shaft and be located somewhere centrally near the technical room in the basement. But it has nothing to do with the wastewater since those are routed directly out of the house via the shortest path.
I would plan a living room that all family members can use together. Give it space where children can play and the rest can communicate.
Parents downstairs, good idea.
Children at night in the utility room? You have to explain that to me!