Building a single-family house with/without a basement on a small plot

The soil survey is still pending, but for the development of the area, one of the soundings was carried out 15m away from our plot:
Groundwater at 2m depth, the soil also contains a lot of clay. In any case, not very permeable.

However, things can be quite different just 15 meters away. Your own survey would be better. It also serves to guarantee the structural integrity.

With 225m² there probably won’t be much garden stuff. It’s actually outrageous that something like this is being sold as a building plot.

Oh hello! No, unfortunately it is not available online and somehow I can’t post the PDF file here. The building area is called "Aufseesianische Wiesen", and on the internet you can find the projects of the architects who participated in the competition.

Yeah, they made a fancy plan there: the main thing is that the city can boast about fancy houses. You can hardly unleash yourself with the development plan, and on the WWW you can already guess the block houses with a 6-meter distance.

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I wonder whether the stepped floor counts as a full floor.

No, that’s why it is a stepped floor.

Just as an example of what would be possible on 9x9 with SG, based on the Villa Casa 131 from bgw (the windows for the garage still need to be relocated): 3 children's rooms, a technical room, a utility room on the ground floor, a separable working niche, a storage room on each floor, and you can even use the roof terrace without having to pass through the bedroom, which then has a panoramic window to the outside, ideally with pleated blinds.

I like the layout of the house. It can work for 2 children. However, not with 3 children and the mentioned study room for the teacher wife.

Personally, I would definitely build with a basement,

Me too. The plot hardly has the capacity to accommodate any outbuildings except a garage. And where to put the vehicle fleet or gardening tools?
Inside the house, you also need enough storage space for 4-5 people. Two crates of drinks in the garage are hardly enough, there are four in the utility room. Seasonal clothes, bedding, sports equipment, etc., all need to be stored somewhere. There is no "I just don’t like basements" or "basements are always so damp and musty."
For me, as a basement opponent, definitely PRO basement!

Another idea, put most of the technology under the roof (ventilation, heat pump,...)

I find the stepped floor way too precious for technology.
Think conservatively: Parents at the very top, children in the middle, living on the ground floor, and technology, crap, and the study in the basement.

Now a few numbers:

Site coverage ratio 0.4 Floor area ratio 0.8

Maximum 90sqm may be built over... maximum 180sqm living space in the full floors. (Phew... I had actually mistaken the quality and read 1.2 0.7 for a WA...)
The stepped floor is a bonus.
The garage apparently counts extra for the numbers and belongs to the site coverage ratio II.

Yes, we will definitely carry out a soil survey.

Think konservatiV: ganz oben die Eltern, Mitte die Kinder, im EG Leben und im Keller Technik, Gedöns und das Arbeitszimmer.

We had also thought of something along those lines.

I once zoomed in on the plan emailed by the original poster: the white hatched area is how the planner envisions the building (so preferably a 6 m narrow "detached terraced house"); the front edge of the house is supposed to be adjacent to the public traffic area; the textual provisions only allow the setback of the upper floor on the west side. The Romans are crazy. However, the plan is a draft, published in May and June 2017, amended in March 2018, and still without entries of public display dates etc. The municipality's website, unlike neighboring development plans, does not yet provide it, so the reference to the not so eagerly adopted building line may mean the expectation that this will still be softened to the building boundary. I have not yet found any indications of terrain elevations. From my point of view, assuming flatness, this is already a borderline plot; if a slope is added, even one for a pathological optimist. Parking space / carport or garage may have to retreat from the building line, but nevertheless, the building line at the front edge of the plot practically implies that the front door threshold could not emancipate itself far from street level. I guess the urban planner has not yet sniffed much of the rough sea air beyond the university campus.

There will be no room with southern sun on the ground floor. Why row houses were not planned here right away - no one knows.

I do too. The property barely has the capacity to accommodate any outbuildings besides a garage. And where to put the fleet or garden equipment?

And a basement doesn’t have to look like it did 20 years ago, it is still a basement

And a basement doesn't have to look like it did 20 years ago, it's still a basement

Exactly. The children's rooms can be smaller because playing and gaming can take place downstairs. A sewing machine and indoor bike would also have space. A child could also learn to play the drums. That wouldn't be possible otherwise. However, one shouldn't worry and come up with "what if" scenarios. If there are no children for the children's rooms, then you simply offer one child a bit more and have some basement space left over. If you are so fond of children, fostering or student exchange might be an option... But for now, the office and the sewing machine can also be located in the children's level.