Floor plan optimization of a single-family house with a basement on a small plot

My thought behind this was that you don't build two full stories completely, but rather a very high knee wall and continue the stairs from the ground floor to the first floor up to the attic, in order to have one or two more rooms there. Similar to the Lichthaus 152 from Town & Country, without the stairs to the attic having to be in one of the rooms on the gable side.

I am now afraid I have understood the following idea (?): the hope is that a first attic / upper floor with such a high knee wall that it just doesn't count as a full story might bring a second attic / loft with another two rooms; and that the stairs can still remain on the eaves side.

[*]The upper area must be excavated to at least 1.5m and refilled. Ultimately, the load-bearing layers - with a bit of compaction - start between 2m and 2.30m
[*]Excavated soil is suitable for modeling the property. In the end, it should be done so that the top, good 30-50cm is set aside, the soil below is used for modeling, and then the good soil is put back on top.
[*]A white tank was recommended (stiff to semi-solid claystone from 2m to 2.30m, poor infiltration). In times of increased rainfall, pressurized water is to be expected; in good weather, not.

Wow, excavating 1.50m sounds like a lot to me. I think I’ll join the basement faction too. I don’t take the terrace thing as lightly as you do. We thought similarly once - after some longer consideration we are now planning to underfill everything with frost protection and have slabs laid. The main reason for me was that such constructions tend to attract tenants underneath. They are quite nice and can live at the shed, but at the terrace I would find that too close smell-wise.

Overall, the terrain modeling plus exterior facilities will probably cost quite a chunk. I wouldn’t bet on doing it yourself unless you happen to have landscapers, civil engineers, and digger drivers in the family.

Did the expert say anything about the thickness of the clay layer and what comes after? It all sounds very familiar to me. With us, drainage was also a problem. Since we had the earth drill on site for our heating anyways, our general contractor made us an overflow. For that, he drilled a pipe through the clay layer (I believe 5 or 6m). So if it really pours and the infiltration gets full, it drains additionally via the pipe into deeper layers.
In the planning I would also make sure that your infiltration is as far away from the house as possible. This soil tends to soak up water, expand, and then contract again. If that only happens locally in a corner of the house, you might be able to imagine what that can mean for the walls.

At 38° gable roof, in my opinion, an attic won’t work - too flat. But if the basement is equipped with windows and finished, that wouldn’t be necessary anyway.

You have to excavate 1.5 m and fill something between 60 cm and 1 m, then you are allowed to go a bit higher

Then a basement can be realized without additional earthworks
Proper windows without light wells are possible
The additional effort for the [Weiße Wanne] remains

The landscape gardener is, I believe, present in the family, right?

Then basement with living spaces

Well, in my opinion, you still need a light court. They don't necessarily have to be excavated separately, but the areas around it do need to be filled up. Or how else should it look?

We are unfortunately laymen in this area

I am afraid this also applies to the city planner who drafted the development plan. As street-side greenery, the ditch could have been designated as belonging to the public traffic area, or at least as public green space, whereby the latter only solves the distance area problem. The access should also be secured in the land register; is there anything about this in the notarized contract?

I’m joining the basement faction too

Ditto. The arguments against the basement are fading, and since it is an explicit wish, the additional costs for the waterproof shell are also acceptable. I also see the terrain modeling as a challenge that requires a lot of experience to get right.

1.5 m must be lowered Ground construction floor slab Parapet height 1 m Max 1.2 and light well omitted Price one or two steps to the front door from the street. I think that is permissible Terrace I would properly fill in on one side of the house and from there stairs and a small slide into the garden which is then at 60-100 cm below street level