Two-family house, optimize?

Number of persons, age 5 persons, 2 adults + 3 children 10, 12, 15

... and 18, so 4 children?

and because after 5+ drawings now it should finally be the final one

Then best show your four previous drafts – that way it could (hopefully) be seen how you proceed in designing.

A full four meters of height in the building envelope – if one exploited it, this would be countered by the limitation to 2 full floors, because from this height difference alone more than one basement level would already result – so you can dismiss the rejection of residential use of the basement right away. I see the following clear consequences from this: 1. not to exploit the building envelope in depth as much as possible, 2. there will be a basement (not only for the "wishful thinking" offspring), 3. I also say cautiously right away: definitely no garage connected on a continuous level by a door. And 4.: the standard of equipment will only be able to correspond to a max. 400 to 450 thousand euro slab-on-ground house, the earthworks, foundation, cellar, lifting system, etc. together consume more than the construction of the condominium. If the plot has not yet been purchased, I recommend continuing to look.

I would gladly accept the help of a professional, only if I have to invest several thousand euros in the basic idea it scares me a bit. The house building company has estimated about 9,000 euros for the architect and therefore we wanted to do as much preparatory work as possible.

The help of a professional – and by that I do not mean an architect contracted by a general contractor – you will undoubtedly urgently need here. Fees may be negotiable, but you cannot do preparatory work here in the form that supposedly completes the preliminary design phase – which incidentally costs quite little in fees.

What this granny apartment costs you more (not only money! above all in quality, because you deprive yourself of some possibilities in planning your own floor plan!) you can give your boy as a rent subsidy for external accommodation...

Considering what a floor apartment reduces construction effort, you can enable the offspring a similarly generous housing unit in a multi-family house in the neighborhood and contribute a rent subsidy at least equal to the cold rent without spending more overall.

Basically, I have to agree with you, I would really like to accept the help of a professional, but if I have to invest several thousand euros in the basic idea, it somewhat deters me. The construction company estimated about 9,000 euros for the architect, so we wanted to do as much preliminary work as possible. Regarding the topic of a granny flat, a contract is to be made with the young man so that I also have a small security and, in case he moves out, I can still rent it out.

1. Don’t just inquire with one company. The slope is not easy and often some curious ideas emerge. But we got a plan from every general contractor (even if it was a model house with windows crossed out on the slope side) with a rough cost estimate and numerous comments without consideration of. 2. Look around here regarding costs, then you will quickly realize you are missing a six-figure amount. 3. Deal with your development plan. can certainly tell you exactly what you are allowed. 4. Make an exact floor plan. 5. Don’t forget the slope, which is completely missing here. 6. You have to downsize, and point 4 helps with that.

My thoughts on the plan: Parking spaces not pushed under the house, but in front of the house. Thus separated from the house, but less excavation. Ground floor/basement or whatever you call it Entrance, living, dining, cooking, building services - terrace (include costs for underpinning) or balcony Upper floor parents, 2 children, laundry, bathroom, access to terrace on the north side. Nicely shady, stays cool much longer and laundry can also go outside Attic the remaining children. Maybe the two eldest with a shared bathroom and mini kitchen unit.

Without a professional or a lot of luck, it will be difficult on a slope. Definitely consider the disposal of the excavation including transport. It happened to friends, the house was built, and a large pile of excavation decorated the future garden. The structural engineer had a five-figure wish list with us. Reinforcement without end and a retaining wall – “the builder just said ‘You’re building a bunker’.” The ceiling between floors was designed thicker. The thickest the builder has ever installed.

Slopes have many advantages, unfortunately, they are not cheap. The budget will not allow much more than 200 sqm, maybe also 240 sqm with clever planning. Which is enough for 5 or 6 people.

One or two sides of the floor in the slope does not make a dark basement, but bright living space possible.

I feared something like that.

If I understand correctly, the reference point is 1m behind the building boundary, so there is a 5m height difference to the street.
Then I have about 2 meters height from the street to the floor slab? How high must/may the basement/garage then be?

if I understood correctly, the reference point is 1m beyond the building boundary

I rather see the intersection of the house front with the existing terrain.

How high must/may the basement/garage then be?

Good question. Boundary-adjacent garages usually have a maximum average wall height of 3 m, which would never work with a longitudinal axis perpendicular to the slope.

Regarding the topic of the granny flat with the boy, a rental agreement is to be made so that I also have a little security and in case he moves out, I can still rent it out.

The boy is 20 until the house is finished.
You also write: "Besides, there are hardly any apartments and almost no houses for rent in our village."
So, are there not many jobs in your village?
The older one will move away in the medium term.
Neighbors of my parents did that, I think the older one only lived with them for 1 year. Then he had a girlfriend and moved in with her. That was in Berlin, they then moved two S-Bahn stations away. Even if there was space for a child in the granny flat, maybe the girlfriend doesn’t want such parental proximity.
Our neighbors were lucky that child 2 was more clingy; he then moved upstairs and stayed for another 5 years and paid rent.
Then it was empty. They didn’t want strangers in the house and the children only lived 30 minutes away by car.