Property development - basement yes or no?

Because as a layperson there is a 90% probability that a tender will not be done in such a way that it really considers everything to 100% exclude that further costs are necessary or inconsistencies regarding interfaces between trades are possible or even a bid creation is rejected because you are just laughed at

If you want a basement and the prefabricated house provider does not offer it – would that be a dealbreaker in the selection?

No. Even if they offered a basement, you can "bring along" your own basement builder, and if they don't offer one, then even more so. The interface just has to fit.

I politely ask around, why should the architect carry out an individual contract award?

The architect does not award contracts at all, he only accompanies the process. The client awards the contracts, the architect prepares the tender. If the architect and the client are smart, first of all, each trade is a separate contract lot, and secondly, they allow bidders to bid on multiple or all lots as a general contractor.

Surely one can do that oneself as well. The architect creates the project and, as the person authorized to submit building applications, submits the documents to the building authority. Afterwards, the client receives the building permit and can do whatever he wants.

Exactly. In a free country, it is completely legal to choose drywall patching instead of detailed planning and to spend as much money on hourly rates as on an entire trade. You can have that fun, but then you simply evaluate the second gastronomic law :)

@blubbernase Did you ultimately decide on a prefabricated house provider? Or are you building with an architect? What was the deciding factor for you?

We have the special situation that we are moving 500 KM away and are already building at the future place of residence. That is why an architect with a tender as a complete offer was never an option for us because we simply did not want to deal with many trades at the same time and so on. And also solid construction not really, because we cannot inspect the construction progress every day over months. That is why we ended up with an "all from one source" provider (Gussek Haus, they also have their own basement construction and for almost everything their own teams) – we also had a local carpenter in the running for a long time, but in the end he ended up at 3200 € /sqm, which we could not afford. At the very beginning we made the usual lists (what we want and so on) and tried to find an architect who would just help us with the floor plan – unfortunately unsuccessfully. We then went to a floor plan service. In the end that was good, because we also abandoned the idea of a granny flat there. Unfortunately they completely ghosted us at some point, and the invoice never came either.... We then planned a bit further based on their work and then approached several providers. Quickly two providers crystallized: Gussek Haus and Schwörerhaus, in the end the Gussek Haus salesperson really put a lot of effort in. If I could do something differently today, I wouldn’t rely on the salesperson’s statement that the Gussek Haus architect would solve our problem areas and would have gotten a second opinion earlier. In my thread this might be all a bit more detailed (just ignore some members’ rudeness).

We went to a floor plan service for that. [...] Unfortunately, they completely ghosted us at some point, and the invoice never came either....

It could have been worse, see:

Please do not dream that this would mean that later cables would be easypeasy to retrofit!

Today we had another initial consultation in which we also touched on the topic of the "installation layer." For us, the installation layer is mainly about being able to hang pictures and cabinets on the exterior wall without hesitation and also being able to add new sockets, etc., in the future if needed.
It's clear to us that this won't be easy peasy because of the installation layer—but we thought this layer would make it possible in the first place.
However, yesterday the statement was made that an installation layer is not necessary for that at all. It's important to ensure that there is no membrane ("vapor barrier") installed in the exterior wall but, for example, a fleece ("vapor retarder"). If a vapor retarder is installed, it doesn't matter at all whether it is pierced by new sockets, nails, or whatever. In plain terms, with a vapor retarder, an installation layer is not necessary (almost pointless). The reasoning didn't seem far-fetched.
Would you agree with that?

Yes, I preferably recommend design, execution planning, tendering, and construction management all from the same source. Of course, the tendering is not only about materials, quantities, and measures but also about execution time windows and price binding periods. I don't know who keeps putting this nonsense in the prospective builder's head that price guarantees only exist with the general contractor (GC).

Thanks—that's very interesting to read. The price period probably starts earlier with the GC—namely with the signature—but you are not completely at the mercy of price increases with the architect either. Are all trades tendered simultaneously by the architect? Or is this done gradually as needed?

There is nothing surprising about apples and pears being uneven in size: the architect means the whole money and the turnkey provider (regardless of type) only the money you want to give them (i.e., whether you get some cash from grandma for the owner-built items). Also, these are premarital promises from used car dealers, and you shouldn't believe them too much. They don't care whether you have to sell the house later to pay for it. They have often experienced that the one with the sweetest promises gets the contract. They don't use your bathroom—so they couldn't care less if you downgrade the tiles again to save the budget.

So, we planned with both including additional construction costs and kitchen. But we are still waiting for the first draft from the architect. He said then he could already give us a closer cost estimate (of course still rough).

For that, take a look at "Changing a floor plan in size," where I explained this in detail.

It was less about that not always being easy but more about that with all providers who only offer catalog houses, you can be lucky if one of the houses fits well on the plot. But if not, it becomes disproportionately expensive with these providers. At least that's our experience/feeling.