Detailed planning floor plan single-family house with basement and granny flat

Why is there a rule that from 40 sqm roof terrace only Kampa or Huf are suitable?

No, there isn't. But a Fiat on a Porsche chassis is unusual. Look at the site I mentioned. You are still flexible. The shower can be used as a turning space. I would leave out the bathtub. You just have to imagine someone using the bathroom with a walker/wheelchair and an assistant.

We are building with Danwood, specifically a house from the Family series. With Danwood, you can generally modify model houses up to a fully custom design, but not with this Family line, where they have set very tight limits.

Yep, that's the LowBudget version.

No, there isn’t. But a Fiat on a Porsche chassis is unusual.

Well, whether it is really comparable to a Porsche chassis, I very much doubt - the sqm price of the basement (including HLS, windows & doors, electrical and flat roof insulation, sealing or greening) is still firmly in the low-budget range, although somewhat more expensive than the ground floor/upper floor. In any case, we had not found a better alternative to implement our wishes within the building window and budget limitations.

That said, I would still be interested in opinions on the layout of the granny flat/basement and additionally have a question that rather concerns the driveway design:

I am not quite sure about the most sensible and visually appealing design of the slope retention along the eastern property boundary - we have to retain descending from about 2 meters height down to 0/street level.

One option would be the shown reinforced earth option, which for my feeling takes up too much space from the driveway width - I’m also not sure whether meaningful planting is possible at this slope.

Alternatively, I had thought of L-shaped stones with the visible side facing inward so that the base lies on my property side and results in the smallest possible width of the retaining wall.

Certainly, a natural stone wall would also look great, but it would surely be difficult to accommodate in terms of width.

Are there any other solutions that perhaps combine the “slimness” of the L-shaped stones with a nicer appearance without at the same time driving costs through the roof?

KNX is also not suitable for low budget. Better to eliminate it and invest the saved 30k+€ into a proper replanning.

KNX is largely EL, so the potential for savings is significantly lower or not really relevant. It's certainly also a question of priorities - some people can't live without a fireplace, I hate looking at switch batteries, let alone having to operate them.

Now I'm also unsure what I should replan - the little things I don't like about the floor plan right now wouldn't really be worth the additional costs to me anyway. But as I said, I welcome concrete suggestions - maybe I'm just overlooking something, you fall in love with your plan.

I would initially leave out the hallway walls to the open-plan living area in the granny flat, 2 meters at the front door are enough. Later, when it is fully used, the room can still be closed off. Bathtub in the bathroom next to the door. Opposite, lined up from left to right: shower, washbasin, toilet. The toilet could probably also go on the right-hand wall. Ground floor (despite promotional house): have the door to the living room closed, door to the kitchen (Danwood builds with panels, so that's possible). A G-shaped kitchen is not functional anyway, built-in cupboards opposite the stairs are unnecessary since there is still a storage room. Upper floor (despite promotional house): door to the bedroom on the short wall, rotate the bed 180 degrees, install sliding doors along the entire width under the sloping roof at 220 -> this creates a nice storage wardrobe with extra depth, where a few boxes of Christmas decorations can fit behind the shirts.