House with slab foundation on a slope

You do not offset any potential savings from reducing the upper floor due to living space in the basement. The floor plan would actually be good for that, to recognize the living space planning, inquire about needs, and thus be able to show alternatives...

I claim the cost overview for embankment, etc. compared to a cellar with living space is more interesting than you think.

we are torn whether we should build there or not. originally, 20K was planned in the budget for earthworks, including terrace, garage foundation, drainage, and trench for house connections.

Wow. That’s already ambitious.

if it is much more expensive, we have to leave it as it is, as said 50K extra for the basement is too much

The utility room and storage room also need space – if not in the basement, then there, where it also "costs" floor area. Let’s say from 150 cm terrain difference, you could level out 30 cm, then 120 cm would remain, and according to my rough estimate this would be about 60% of the cost of a non-built basement compared to a built basement.

I don’t necessarily see the dream house slipping away because of that, but for a "ground-level" house you would need a level plot.

as said, 50k extra for basement is too much

I would leave out the word basement and rather define a single-story house (bungalow) with a lower ground floor, so a living basement. It has come up quite often, but the knot doesn’t seem to untie for you. However, you can’t just use a standard house for that; instead, the sleeping units may be on the ground floor, the living rooms with utility room etc. in the lower ground floor... the site plan hasn’t been posted yet, has it?

20 t for earthworks including support according to the specifications of the structural engineer
It will not be sufficient

Move away from the idea of a basement (dark, musty, junk room, for oil tanks)

I would spontaneously plan a carport in the east. Support it with L-shaped stones, steps to the house entrance.
In front of the house, plan a parking space directly at the entrance.
Mirror the floor plan, building services in the east, kitchen in the west

The outdoor area then also does not need the terrace to be filled and supported by 1.5 m. It can be done like Nordlys did, with natural stone or planting stones

The ground floor will then not be constructed with a timber frame

I don't think you will be happy with this land. The 50 grand will probably be unavoidable anyway. A slope is simply more expensive than flat land. Period. If the budget can't handle it - keep looking.

Thanks for the input, we already understood that this is not about a musty storage cellar but rather about getting the house itself.

What makes me suspicious is the slope, I have been on site several times and after 1.5m it doesn't look like that on the building plot.

The street to the north seems to have the slope, but the building plots are much flatter... has it maybe already been leveled? And if so, what does that mean for our plan to build with a foundation slab?

I can only remember the offset of about 40-50 cm at the left property boundary to the street (runs from east to west down the hill, remember). Furthermore, the plot is level at the right property boundary to the street??? Could that be due to the cross slope? (see excerpt from the development plan). But then the 1.5m slope of the street would have to have "disappeared" somewhere on the plot..., but you can't see it!...

As part of the soil survey, 2 boreholes were measured to a reference point of the street, and lo and behold, the 1.5m slope is there again. Do you have any idea and is that rather good or bad for us?