Procedure for constructing a new single-family house on an existing plot

That means I set the zero point in the rear left corner (as seen from the street).

That is unfavorable for your planning mindset: water never flows uphill, and your elevation reference point will probably be oriented more toward the street than the valley floor of the property.

One could go out into the garden from the basement level at ground level, but the ground floor is a bit high for a nice access to the garden.

I recommend that you do not refer to the street level as the "ground floor," and regarding the slope garden topic, search the forum for the keyword SupaCriz.

What do you think about earthworks and costs? Will we actually get a basement here "somewhat cheaper," since earthworks would also be necessary for a house without a basement?

I would put it less positively, but yes: the earthworks involved in placing a house on this plot will only require the excavator bucket to make marginal detours to conveniently carve out a nice basement pit on the way ;-)

Unfortunately, there is no comprehensive sketch in post 1 where one could quickly check this. And I am not going to read the entire thread again.

Even more unfortunately, there is still no useful contextual information from the other participants: no aerial photo, no cadastral excerpt, no development plan (please provide meaningful ones, not narrowly cropped!). According to the sketch in post #36, the property borders on expectation land at the bottom of the plan, i.e., a different "usage type." This calls into question the building plot boundary shown (as in block perimeter development).

Good morning,

That is unfavorable for your planning mindset: water never flows uphill, and your height reference point will probably be oriented more towards the road than towards the valley floor of the property.

Sure, I understand. I didn’t want to indicate the heights with "minus meters". But I think it’s clear how the heights develop.

Thanks for the hint regarding the other topic, there are certainly parallels. I suspect that our slope is a little flatter, which hopefully makes walking through the garden from the living area easier. However, I don’t find the ideas bad.

I would phrase it less positively, but yes: the earthworks in connection with placing a house on this property will only demand marginal swings from the excavator bucket, in order to also put together a nice basement pit on the short service route ;-)

Okay, sure it’s both effort. But that probably confirms the architects right that a basement is at least advisable here :-)

Even more unfortunately, there is so far no usable aerial photo of the fellow discussants: no aerial image, no cadastral excerpt, no development plan (please each with meaningful extent, not just narrowly cropped!). According to the sketch in post #36, the property borders on development land at the bottom of the plan, i.e. another "land use type". That calls into question the building boundary as shown (as with block edge development).

I find it difficult to publish these documents here. They do not "belong" to me. I think the sketch provides the important information.
In the development plan, of course, something is also planned for the development land. The building window stretches as a long, 18m wide window completely from the built neighbors to the development land. The only limiting specification from the development plan is the maximum building height (GHmax) of 8.0m.

Is it really true that the land in the east is much flatter than in the west? Show some pictures of the property. Your sketch is also not exactly to scale.

Yes, the sketch is very rough and it was initially only about a rough assessment of this height profile. It tapers off slightly flatter towards the east corner, which is depicted too drastic in the sketch.

If the development plan is online (which I suspect), then parts of it can be shown. I can hardly imagine that only one specification is regulated in the development plan.

You surely have a plan of the property, at least there should be a property plan in the notary contract.

In the Geoportal, there are regularly also elevations.

If an architect is already involved, then there should also be a survey plan with terrain elevations. You should at least show that.

You already have the property, so why can't you provide more detailed information?

In my opinion, UG and EG are more likely a solution here than the basement. But unfortunately, this cannot be judged with so little input.

The terrain is twice as steep on the first half, if your contour lines are correct.

Yes, the sketch is very rough and it was initially only about a rough assessment of this height profile. It tapers off slightly flatter towards the east corner, which is depicted too drastically in the sketch.

Then give me the opportunity to make it a bit more precise.