Build a house, buy a house, or...?

So, roughly the following is stated in the development plan. I can't make much sense of many of the details, as I am (still) not very familiar with the subject.

[*]Floor area ratio 0.4
[*]Plot ratio 0.8
[*]Visually, the building complex on the valley side should only appear to be two stories (this apparently is not taken too strictly, since my parents, for example, look like 2.5 stories high on the valley side with a basement)
[*]The 2nd full story should be constructed for design reasons either in the base or attic floor
[*]2 full stories allowed
[*]Open construction method specified
[*]Distance 3m to the street boundary
[*]Garages may be built on the property boundary
[*]Gable or hipped roofs permitted
[*]Roof pitch 25 to 45 degrees

I think this is the most important for you?! If anything is missing, feel free to ask anytime.
Regarding the plot: 550 m2, sloping location, although I can't estimate the gradient at all. It is not extreme; I have to ask my parents if they have any information about it for their plot. Plot 2135 belongs to my parents, 2134 is ours, and 2133 belongs to my mother's brother, who will not build there and would first ask us if he wants to sell it.

There should also be a site plan with contour lines available for the property. Just take a look on the respective municipality websites. The slope and how steep something is are often underestimated in the normal view. And then incidental building costs of 40,000 euros (what is that supposed to include? And how much of the equity do you want to keep back for necessary other things like the kitchen, etc.?) are not that much.
https://www.hausbau-forum.de/threads/liste-der-anfallenden-Baunebenkosten-bauseits-teurer.9737/
and
https://www.hausbau-forum.de/threads/warum-ein-Hausbau-fast-immer-teurer-kommt-als-kalkuliert.16237/
as "mandatory" reading.

My wife is already more in favor of building without a basement (because of the costs).

Here’s another idea from me regarding the storage room issue...

We are also planning without a basement because a basement is simply way too expensive for us. I think the numbers mentioned here are not unrealistic. Depending on the soil conditions, you quickly reach 70 to 80 thousand euros. Of course, there are also plots where you have to build with a basement due to the steep slope. That’s something different... It’s best if you inquire. Otherwise, your entire budget planning might end up being completely thrown off.

We are currently planning a single garage with extra length so that behind the actual garage there is an additional storage room for bicycles etc. The costs are only a fraction of those for a basement.

You can always still build a nice garden shed later for gardening tools.

There is still plenty of space in the attic for decorations and other stuff.

Better put the money for a basement into a better energy efficiency class or other additional equipment. In the long run, you will really get more out of that than from a golden (and wasted) storage option.

By the way, your ancillary building costs seem very low to me. We have allocated 25 thousand euros just for earthworks, and that even though probably not even any soil has to be removed for us... We can most likely distribute it on the plot. Our plot is pretty flat... The steeper the plot, the more expensive the earthworks become.

Have you already obtained a soil survey? If you have decided to build, it would not be wrong for further planning. Sooner or later you will have to have one anyway...

Hello,

thank you already for your responses.
We are slowly making some progress and have a quote from a prefab house company, but after careful consideration, we no longer like it. With this company, everything somehow happened very quickly, and it gave the impression that they wanted to create some pressure and close the deal as soon as possible. This company did not even visit our property but still submitted a comprehensive offer including a price for a basement. The next step, according to the company, would now be a factory visit with "dinner at the Italian restaurant." I initially declined this and asked for time since we want to get more offers from other companies, but again a date for a meeting is being requested. I will ignore this for now and speak to the company again at the appropriate time (if it is still an option) or cancel otherwise.
A second meeting with another prefab house company went significantly better. First, the property was viewed, followed by a 3 1/2-hour conversation about ideas, requirements, wishes, and possible problems. This company will now first create a drawing based on a model house from their catalog with our wishes, and then another meeting at the factory (near us) will follow. The agent lives very close to us and was not really convinced of a basement after viewing the property since he estimates that the basement would need to be a "white tank" and could cost around €100,000 in total (depending on the basement's fitting).
In addition, the basement would stick out about 1m from the ground, and our wish to have relatively level access directly to the terrace and the lawn would only be possible with difficulty. The basement could be completely filled in, but that would cause costs again and basically be an expensive "buried" storage room.
So, we have more or less accepted now not to build a basement. The consideration is also shifting towards a garage or a double carport with a storage room.

Regarding incidental building costs, the gentleman from the 2nd company wants to determine a cost overview for our building area. He estimates the incidental costs at about €35,000, but we had initially budgeted €50,000 in joint planning. For example, he estimates €20,000 for the earthworks.

I had my parents look up the costs for the earthworks for their new build. They have significantly more slope than us and built with a basement. They had an invoice from the builder (an acquaintance, but nobody from the circle of friends or so) for just under €6,000, of course almost 10 years ago. He also dug away a slope in our garden the year before last, and I will ask him to make me an offer when I have a first draft of the house. I'm curious.

We have the following ideas for the house planning:

[*]Living space approx. 140 - 150 m2
[*]Gable roof (knee wall approx. 1.30m)
[*]Bay window
[*]Fireplace connection
[*]Separate kitchen with sliding door
[*]WC with shower and an office on the ground floor
[*]Niche/corner for wardrobe in the hallway that is not directly visible (very important to my wife)
[*]Living room with access to terrace/garden (relatively level)
[*]Upper floor: 1 x bedroom, 3 other rooms, bathroom
[*]Cistern for rainwater buried in the garden with connection to a water tap
[*]Photovoltaic (at least preparation so that there is the option later)
[*]Possibly geothermal energy if worthwhile (I will look into it)

We agreed that scaffolding, construction site toilet, and construction fence would be included in the incidental building costs.

What will be determined:

[*]Building permit
[*]Earthworks
[*]Road closure
[*]House connection/sewer works
[*]Gutter connection
[*]Possibly retaining walls
[*]Kitchen
[*]Construction power/water
[*]Surveying
[*]Financing costs
[*]Insurance (builder's liability, fire shell construction)

We are still considering a soil survey. The gentleman from the 2nd company said if he were building there, he would skip the soil survey. A good friend also built nearby without a soil survey, and my parents built on the adjoining plot with more slope also without a soil survey. Today this would probably not be possible with a basement anymore, but without a basement it is possible. The area used to be fields for agriculture (cows grazed there decades ago).

Thank you for your feedback!

My tip. According to your report, the prefab house builder number 2 would be shortlisted. Number one would be out, a waste of time. Number three would be a classic solid builder for me, but regional, not Viebrockhaus or Heinz von Heiden or something like that, and then decide. Don’t drive yourselves crazy with 10 providers.

That is the question, we are still considering going to [Fingerhuthaus] because they are also nearby, but according to company No. 2, the prefab house companies located here differ only very slightly with the same quality. We really ask ourselves what makes sense.. How many companies should we check out? We are actually going to have a meeting with a company that builds massively but also "turnkey" and will get some advice there.