Planning guest WC in new construction - How big should it be? (DIN?)

Okay convinced.

Regarding the building authority: A comprehensive clarification took place with the building authority. With a clerk, the responsible city planner, and an independent third opinion (a friend of a friend who also works at the building authority and gave an independent, favorable view of the planning but still had to agree with his colleagues). The office made it very clear what it will approve and what not. We have tried many things with the office in many exhausting rounds. The project has a certain history which is irrelevant here. Just believe me: The exterior dimensions are fixed. It can't be higher either because then we would not comply with the distance to the neighbor on the left.

Regarding the guest WC: I don’t see it as a waste of space as long as it is very small.

General contractor: We are in close contact with our building partners and reputable general contractors (final decision pending). After a complete failure with a large solid house company, we have become much wiser regarding the choice of construction companies.

And now the moment of truth. Our floor plans for the ground floor and upper floor (attic will be a study and has not yet been drawn).

Ground floor:
- Hallway, guest WC, utility room, open plan kitchen/living area

Upper floor:
- Bedroom, child’s room, bathroom, hallway, broom closet

Sorry for the rough dimensions, I had to enter them manually. All dimensions except for the two marked ones refer to the interior dimensions. Terrace has not yet been planned and is only for orientation.

Walls: Exterior 36 cm, interior 17.5 and 11.

2 full stories + attic

Furniture and sanitary fixtures have been roughly inserted and should not be regarded too strictly. The window planning and door swing directions also serve only as rough orientation.

Goal of the plans: As much open plan kitchen/living area as possible, enclosed staircase (debatable), as much bedroom and child room as possible

The feasibility of the utility room is still being clarified. Whether it needs to be bigger or can be smaller, I don’t know yet.

I would design the kitchen smaller to have more living space. I would orient myself more towards tiny houses or even trailers and galleys, instead of trying to imitate the layout of a standard 160 sqm ground floor. Or I would take more inspiration from old eat-in kitchens. And I would plan the staircase in a way that the storage space can be used to the maximum. Either as a WC or for kitchen or wardrobe cabinets. You need zoning and not a large open area.

I think the floor plan makes good use of the less than optimal house shape and is otherwise quite well thought out. I would consider whether you will be happy with such a tubular bathroom. Otherwise, from my point of view, the house can be built as is. Of course, I would add a window to the utility room! And some storage space under the stairs.

Cooking is an essential part of our daily lives. The kitchen is allowed to take up a large part of the available space. I don't find a 32m2 open-plan kitchen so small that I would have to put a camping stove and 2 folding chairs in there.

I am missing the roof orientation, the knee wall height on the upper floor .. or roof only from the 2nd upper floor = attic?, the overall plot location, the check whether technical equipment can be installed on the upper floor.

I would not plan the kitchen any smaller under any circumstances, it is also well positioned towards the terrace. Living/sofa/TV - in the quiet, slightly secluded corner is realistic and with today's TVs it does not have to be much bigger. 8.52*7.72 are after all not ballroom external dimensions.