Assessment of the floor plan for a semi-detached house, flat roof with full basement

You can do that, but they have to stay somewhere - if invisible, then in a correspondingly thicker wall. However, I don't really see the space there either.

With Bauhaus style and a budget of up to 800,000, I do see room for solutions. With the square meter areas, you don't have to fight for every centimeter like with a 140 sqm house. I wouldn't hang up on that now. I don't like the huge bathroom because there is a lot of useless space (2.50 m by 3.00 m walking area?), but I can't think of a better solution for the upper floor layout either. The staircase is just very massive.

I understood it as the wastewater being brought invisibly at floor level along the exterior wall and then drained around the house through the garden towards the street. So it is not first brought into the basement and then pumped back up from there. However, there are no detailed plans for this yet, as we are still in the design planning phase.

With Bauhaus style and a budget up to 800,000, I do see room for solutions. With the square meter areas, you don’t have to fight for every centimeter like with a 140 sqm house. I wouldn’t hang up on that now. I don’t like the huge bathroom because there is a lot of useless space, but I can’t think of a better solution for the upper floor layout either. The stairwell is just very massive.

The stairwell is indeed, I would say, planned comfortably. It is supposed to be a concrete staircase with straight steps and exactly this intermediate landing. Of course, a space-saving option would be a spiral staircase. I can hardly imagine a straight staircase with the building envelope, since it is too large for a single-row room layout (as is planned in the usual 6m-wide terraced houses) and too small for a double-row room layout (i.e., rooms on both sides on one level with a corridor). Indeed, I think the staircase is the decisive structure for the overall layout.

So it is not first brought down to the basement and then pumped back up again.

Normally, connections for wastewater are located below the ground surface, typically somewhere "on the wall" in the basement. So nothing would be "pumped back up" from there. I would be very surprised if the black water is routed outside the building envelope, especially since the pipes would then need to be insulated accordingly and would therefore take up (even) more space.

Of course, it is only a detail, but I would clarify this exactly before signing (and have it assured to me) so that your guest doesn’t end up complaining about noises next to their pillow later.

I understood it to mean that the wastewater is brought invisibly at floor level along the exterior wall and then drained around the house through the garden towards the street. So it is not first brought into the basement and then pumped back up from there. However, there are no detailed plans for this yet, as we are still in the design phase.

It can be done, but... the necessary shafts in the exterior wall tend to show discoloration on the facade after a short time because the thermal exterior envelope is no longer completely homogeneous. Especially on shaded sides, this can quickly become unsightly. When working on these downpipes, access often can only be gained through an opening in the facade. I recently had such a case at work, which gave everyone involved very little pleasure. You may end up paying a high price for a nice appearance.