12x9.6m 2 full floors, basement, attic, 4 children's rooms

Most will do like Kaho's Omi and stay in the familiar rooms as long as possible. We have not planned for sleeping on the ground floor. Nevertheless, no thresholds have been installed anywhere, wide doors and turning areas have been taken into account. At some point, there comes a time when steps and thresholds become difficult.

Let's all hope to stay healthy into old age... but in case that's not the case, I have expanded the shower to 150x150... and drawn the window in the guest WC.

Go shower somewhere with such a large shower. We have 1m x 1.40m - I think that's just not too big yet. Any bigger and I would be freezing in the shower.

...I once enlarged the shower to 150x150...

Perhaps a bricked-in (drywall) vent pipe of about 10-20 cm will be added, leading upwards over the roof, for the drain down below - then nothing can be done with a fixed shower tray (like enamel) in that size (tiling around the corner is of course also possible).

Possibly there will be a bricked-up (drywall) vent pipe of about 10-20 cm, led upwards above the roof, for the downward drain as well - then nothing in that size with a fixed shower tray (like enamel) (tiled around the corner of course also works).

Quite right. I think it will only be tiled and there will be a curtain in front instead of a door. That also offers some flexibility. I also considered routing the controlled residential ventilation supply and exhaust air out of the wall in the corner.

I would prefer to place the staircase on the right side of the hallway instead of the left side, so you can sit a bit more "protected from view" in the living room.

Best regards
Sabine

I would prefer to place the stairs on the right side of the hallway instead of the left, so that you sit a bit more "screened" in the living room.

Best regards
Sabine

Unfortunately, it does not fit with the guest WC and the front door would be directly at the garage. I would also not want to push the latter further back.