How to build a massive single-family house most cheaply?

Due to a limited budget, it should of course be as cheap as possible.

Rather basic without frills, probably without a basement, about 160 sqm of living space.

With 160 sqm, there is already some spatial frill? A dressing room? A children's bathroom? Or a pantry?

But at 160 sqm there is already some spatial frills? A dressing room? A children's bathroom? Or a pantry?

With 160 sqm for 5 people, there is hardly any room for frills.
At least not when I think about what I constantly read here regarding the necessary storage space for 50 winter jackets, 100 pairs of shoes, enough space in the hallway for 8 people to get dressed at the same time, etc. So basically what is considered necessary to be able to live "decently" in a house...

Because a "dressing room" in such house dimensions is usually nothing more than a niche separated by an interior wall where wardrobes stand. So more like a walk-in closet. I don't see a children's bathroom or pantry at all on 160 sqm if you want 3 reasonably sized children's rooms with 15 sqm each. Although a second shower or at least separating shower and tub should definitely be reconsidered with 5 people.

If 3 teenagers shower, the bathroom is blocked for hours daily.

PS:
Better to do without parquet, expensive designer kitchen, Q4 smoothed walls, expensive designer ceramics, flush-mounted fittings and whatever else, than to end up with 10 sqm too little.

A so-called children's bathroom is usually not the second bathroom in the house, but the second one on the upper floor. In addition to the guest bathroom on the ground floor, making a total of three bathrooms. That is rather a luxury.

However, it is also possible to manage with less than 160 sqm with 3 children's rooms, for example the [Flair 134]. It is also visually much more appealing and fits into more development plans than an [Anstattvilla]. But that may just be my taste ;) When counting square meters, it is also crucial how additional square meters are distributed. As long as we don't have a room program and budget from the TE, the whole discussion is pointless.

Phew... the Flair 134 offers 4 rooms of 10-12m² each in the standard version upstairs.
And that at a current price of 257,000 EUR in the Kreis Minden and Osnabrück area (I found that quickly, prices in the south are usually 10-20% higher). That would be 1,917 EUR/m².
The Flair 152, on the other hand, is listed there for 279,000 EUR and thus comes to 1,835 EUR/m². And with the Flair 152, the second shower in the guest WC is even included in the current standard...

I think the 22,000 EUR for a real full floor in the upper floor and 18m² more is definitely worth investing. Better to save elsewhere.

It's a very good example that you can’t simply scale m² with 3,000 EUR/m² across the board.

I don't see a children's bathroom and pantry at all on 160m²

That's no problem, because you're not even asked.

Yes, costs do not necessarily scale linearly. Still, you can save a chunk of money with 30sqm less.

In general – as one knows from car leasing – fewer square meters are not necessarily cheaper just as more square meters are more expensive. The "rule of thumb" often heard from general contractors, that the price is the same with a different floor plan if the size does not change, is often misunderstood as a "price per square meter," but actually means: "please don’t ask us a dozen times for a current price just because you thought of a new iteration of the floor plan."

With 160sqm there is already some spatial frills? A walk-in closet? A children’s bathroom? Or a pantry?

To get a result of 160sqm for a 130sqm space requirement, you do not need any frills at all. It is absolutely sufficient just to accidentally / awkwardly include "empty square meters" as an amateur planner. A GC (general contractor) apprentice is, in this sense, also an amateur planner!