Preliminary draft single-family house 12.4m x 9m, 2 stories, 22° roof pitch.

We have just under 6sqm of utility room and it will be tight when everything is completely finished.

A 6m2 utility room is not a technical room :) Technical room means: heating, electricity, water, gas, possibly a ventilation system, and that's it. No washing machine or anything else.

Based on that, you want to invest a six-figure sum in euros?

It's not simply done with 3 lines to adjust this floor plan. The spatial arrangement of the bedroom and dressing room is not workable at all. You can neither place proper wardrobes in the dressing room because of the windows, nor can you fit a proper double bed in the bedroom.

I find the bathrooms on the upper floor to be quite large as rooms. They offer a lot of open space.

In my opinion, the stair starting point on the ground floor is much too close to the exterior wall towards the entrance. That will be rather uncomfortable and not spacious.

A 6m2 utility room is also not a technical room :) Technical room means: heating, electricity, water, gas, possibly ventilation system and that's it. No washing machine or anything else.

Thank you very much for the lesson. In our utility room, sorry, HTR there is:

water, sewage upper floor, well system, heat pump, brine line, hot water storage tank, expansion vessel, heating circuit distributor, main electricity junction box, fuse box, photovoltaic control, patch panel, multiswitch and last but not least some space for the installer(s) to move around... and no controlled residential ventilation... if there were one, the room would burst...

:-) Ok, then that was a misunderstanding. With so much, it really gets tight.

But you can still get the mentioned components together quickly nowadays.

Originally we had 11sqm, during the planning it kept shrinking and at 5.8sqm and an offset in the wall our planner thinks that's it now.

And when our electrician and plumber found out what all has to go in there, they just gave a friendly WTF... So it’s doable, it’s not cramped yet, but our plan to put in 1 or 2 more shelves is "dead".

It's true, nowadays a lot comes together. Except for [Photovoltaik-Steuerung] and [Brunnenanlage], we have everything you listed. However, we have installed the heating circuit distributor in a storage room under the stairs. It would have fit into the technical room, but the heating technician preferred a more central location, and it doesn't bother us in the storage room. Hehe, yes, our installers also huffed and puffed, but in the end, everything worked out. And without major problems. That's why I wrote that if they have 12m2 available, they will definitely use it. Under our fuse box, there is even space left for a shelf for the drill and other tools.