Cost estimate single-family house 600m³ + basement

Good evening everyone,

unfortunately I can't reach my architect this week... so I sat down myself and calculated the following:

square floor plan, the attic is directly above the ground floor (still not supposed to be developed ;) with a 0.5m knee wall.

Ground floor:
10m x 10m x 3.10m = 310m³

Attic (knee wall):
10m x 10m x 0.5m = 50m³

Attic (roof slope):
10m x 10m x 5m :2 = 250m³

Total attic: 300m³

Since the attic is not supposed to be developed, you only calculate it at one third. -> 300m³ : 3 = 100m³

Accordingly, I come to a building volume of 310m³ + 100m³ = 410m³

According to the calculations from the previous plan and research on the internet, I have estimated costs for a turnkey house at €350 per m³.

410m³ * €350 = €143,500

Let's round that up to about €150,000

This number seems so small... Do I have a mistake in my thinking? Can't the attic be calculated at one third? (If I calculate it fully I come to: 310m³ + 300m³ = 610m³ -> 610m³ * €350/m³ = €213,500)

I hope you can make sense of my calculation and help me through my sleepless nights...

Thanks in advance

Here in the forum I have now always read posts with 1700 Eur per sqm living space, as a guideline. I think about 50 teur more for the basement. I asked around. My bank calculates with 425 per cbm.
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With €320-€350/m3 GFA you can get a good first cost estimate for a very simple house. However, additional ancillary building costs of about 16-20% apply (fees, charges, financing costs). The construction costs refer to cost groups 300+400 (building structure + technical equipment). Not included are the outdoor facilities, the garage, or interior fittings (kitchen, lamps, furniture).

Alternatively, approximately a gross €1,850/m2 net living and usable area can be calculated, including ancillary building costs, for a very basic standard.

Why do you want to build such a large, unused attic? About €90-€100/m3 GFA is charged for that. If you are interested in a small basic house as a "cube," it could be optimized if the development plan allows a flat roof or another roof shape. The gross 100m2 must then be very well distributed so that the floor plan works.

The dg is planned to be expanded in a few years, if children come. Since I am initially undertaking the project financially without a partner, I would otherwise overextend myself.

Good evening,

EG:
10m x 10m x 3.10m = 310m³

What clear height is the target and how is the floor slab/ceiling structure planned?

Storage (knee wall):
10m x 10m x 0.5m = 50m³

No. 10.00 + 10.00 + 10.00 + 10.00 x 0.50.

Storage (roof slope):
10m x 10m x 5m :2 = 250m³

Depending on the above calculation method: up to 1.00 m = 0, from 1.50 m = 50%, from 2.00 m = 100%

..do I have a thinking error?

Several ... which is normal, since you are a layman ;)

Rhenish regards

Good morning construction expert,

Thank you for your answer.

What exactly is meant by clear height?

No. 10.00 + 10.00 + 10.00 + 10.00 x 0.50.

I wanted to calculate the volume of the rectangle where the knee wall is located. Length x width x height

According to your information about the roof, the enclosed space would become even smaller. Isn't this distinction only made for the effective living space?