Preparing the site for the floor slab on a slight slope

Hello everyone,
we are planning to buy a plot with a slight (?) slope.
As can be seen in the attachment, the plot is between 24m and 37m deep and 16m wide. However, 3m width of the plot is "blocked" by an [Erschließungsbaulast], and no changes should be made in this area.
I have marked the possible building area once and our preferred footprint (dashed line) once on the plan.
What we are now wondering is how high the effort is to build on this plot with a slab foundation, i.e. without a basement. As you can see, there is a height difference of up to 80cm within the preferred building area. On the other hand, there is also a height difference of about 60cm from the edge of the desired house position to the [Erschließungsbaulast]. The distance between the desired house position and the [Erschließungsbaulast] is approximately 1.6m.
A soil survey is currently still in progress, but generally, clay soils are predominant in our region.
We are now wondering to what extent the plot is buildable as we imagine it and which measures (e.g. supporting the plot towards the [Baulast]) are necessary.
We are also willing to consult a professional, but are not sure where the right point of contact would be.

Best regards and thanks in advance
Perigrin

Basically, that is possible. You just have to expect that the house at the lower corner will extend quite a bit and that on the base slab there will be about 15cm of screed and flooring added. So you end up significantly higher than you would originally think.

If I now take the 87.7m as an orientation for the ground floor floor height, then you have about 1.5m height difference at 1.6m space for the driveway. That would be roughly a 45-degree slope. That would already argue for a wall, since the house sits directly on it. With that difference, it is definitely worth considering raising the ground floor a bit and building a basement underneath, as at that point there would be enough window area possible even without a light well. A study, hobby room, etc. can be well accommodated there.

Thank you for your response. Unfortunately, financially we cannot afford a basement. Do you mean a wall that only supports the slope or the house? I imagine a wall that supports the slope to be significantly more cost-effective and, above all, we could still build this later and consider whether we want to fill up to ground floor height.

we are planning to buy a plot of land with a slight (?) slope. [...] As you can see, there is a height difference of up to 80cm within the favored building window.

I would at least still consider that a "slight" slope on its own, and according to the 11ant basement rule it is associated with expected basement costs of 40%.

Unfortunately, we cannot afford a basement financially.

If that is the case – which we have not been able to understand so far – then this is a big red question mark behind your building wish. If your budget is categorically intolerant to even minor complications, that translates into a tiny ideal plot. You would probably be better off with an offer from a developer then.

However, 3m width of the plot is "blocked" by a development easement; no changes should be made in this area.

That would then require explanation: Easement in favor of whom / which development, and the changes presumably mean leaving the terrain there unchanged (?)

... and according to the 11ant basement rule, it would be associated with expected basement costs of 40%.

How exactly am I supposed to understand that?

If that is the case – which we cannot comprehend so far – then that is a big red question mark behind your building wish. If your budget is categorically complication-intolerant, that amounts to a tiny ideal plot. You would probably be better off with a developer's offer then.

Here I should probably not be too biased, a basement is not categorically excluded.
A buffer is planned in the budget at several points, which we of course want to keep as long as possible.
We expect costs of up to approximately €400,000 for the house including the foundation slab. If we now build smaller with a basement, that would probably reduce the cost increase somewhat again.
To bring the plot into a condition buildable with a foundation slab, we have calculated with €35,000–€40,000.

That would require explanation though: building encumbrance in favor of whom / which development, with the changes probably meant to leave the terrain there unchanged (?)

The building encumbrance is an asphalted path that leads to the property behind. Since it has to be passable, we cannot simply cover it with earth, for example.

How exactly am I supposed to understand this?

My (also incredibly often and precisely accurate for myself) rule of thumb states that a basement where it would actually be required according to the "opinion" of the property 1. in principle generates avoidance costs approximately at the same level as construction costs and 2. that this principle is likewise partly valid, namely according to the formula "10% per 20 cm height difference in the building envelope". You are talking here about 80 cm, so the formula results in the conclusion that for earthworks, "L-walls" and the like you would have about 40% of the costs of a built basement on the bill for an unbuilt basement.

I probably shouldn’t be too biased here, a basement is not categorically excluded. [...] If we now build smaller with a basement, that would probably reduce the cost increase again somewhat.

However, the potential for reallocating space into the basement is moderate in the present case. You will probably only "shift" the above-ground basement replacement space here, but hardly be able to create economically sensible living space in the basement.