Cost estimation for bungalow with basement KFW40

Good evening,

due to the current KFW300 funding, we are considering building a house.

Because of the hillside location, it is planned to build a basement, which is mostly intended to be done as self-construction.
Half of the basement should be used as living space.

I would like to place a bungalow with a walkable attic on the basement.
The footprint of the house should not be larger than 80sqm. I find this completely sufficient for me.
(80sqm bungalow + 80sqm basement)

The plot is already available and has 1,000sqm.
Due to the size of the plot, I would like to use geothermal energy.

The current funding is only available if the KFW40 standard is met.

Can you give me a rough estimate of the construction costs?
I would prefer to place a prefabricated bungalow on the basement.

Many thanks

Due to the current KFW300 subsidy, we are considering building a house.

Interesting reason. Usually, you build for the house itself - space, individuality, absence of neighbors, garden, oasis of life, for the children, etc.
If the (small) subsidy is a reason for you, it is a poor one.

The plan is to build a basement due to the hillside location, which should mostly be done as self-construction.
Half of the basement is to be used as living space.

Can you give me a rough estimate of the building costs to expect?
Preferably, I would place a prefabricated bungalow on the basement.

Also an interesting approach.
Self-construction:
- WU-basement due to hillside location – can you do that?
- The basement is also living space. Who will handle the interior finishing?
- Who takes over the warranty for the house construction if building on a self-built basement in difficult terrain
etc.

Without going further into your concept and without being able to assess the self-construction (including foundation).
If the house were built in the usual way, I would estimate from €300,000 for living space (100 sqm - pure construction costs) and from €60,000 for the basement part. Of course, there is also the issue of additional construction costs with earthworks, etc. On a slope, these can quickly add up to €50,000 to €100,000. Finally, the outdoor facilities, driveway, terrace... are still missing.
A bungalow is overall also somewhat more expensive to build than the typical "2.5-story house". The bungalow has a poor ratio of exterior surface to living space. So, additional effort for insulation (especially on a slope) is to be expected.

60 thousand euros for 80 sqm WU basement with "KfW 40"-like insulation is a bit optimistic - I would estimate 1,000 € per sqm for a raw basement, that way you are on the safer side.

60 thousand euros for 80 sqm WU basement with "KfW 40"-like insulation is a bit optimistic - I would assume 1,000 € per sqm for the shell basement, that way you are on the safe(r) side.

Calculated differently. 120 sqm base area x 0.85 = 100 sqm living area. Of that, 2/3 above ground and 1/3 in the basement. The basement share with at least 3,000 € per sqm. In addition, the "real" basement with 60 thousand euros (but then only 34 sqm).

Due to the current KFW300 subsidy, we are considering building a house.

The floor area of the house should not be larger than 80 sqm. I consider that completely sufficient for me.
(80 sqm bungalow + 80 sqm basement)

Do you have children in the household?
And what is the total household income? Under 60,000€?

About the budget:

The footprint of the house should not be larger than 80sqm.

I assume that 80sqm of living space is meant.
And then I calculate a 160sqm house, ground floor with finished basement, auxiliary rooms located in the basement: simply 160sqm x 3000€, so 480,000€ without own contributions plus the usual costs such as incidental construction costs and outdoor facilities.