white tank as living space

Thank you for your quick responses.

So the entire project will grow from 50k to rather 70k+.

On Google, you often read that a partial basement wouldn't be worthwhile. If I were to choose 8m x 6m instead of 10m x 10m, to what extent would the price approximately decrease? So from the 70k+ downwards?

Thank you all

Since you already have an offer, I would simply request both additional variants.

On the exterior walls, we also have exposed electrical installations due to WU concrete, but where possible, we install them flush in the interior walls. We also have 12 cm of perimeter insulation on the outside, which would have been applied anyway if it hadn't become a residential basement.

Since controlled residential ventilation was planned anyway, we connected the basement to it right away. For this reason, we omitted the typical small windows with light wells, which only cause dirt and are a potential weak point, but do not provide sufficient light.

Instead of radiators and thus two circuits with different supply temperatures and an additional pump, we decided on underfloor heating for the basement as well.

For that, the typical small windows with light wells were omitted, which only cause dirt anyway and are a potential weak point, but do not provide sufficient light.

So no sunlight at all?
How do you want to use the basement?

+ Costs of 10-18 euros /m3 for the disposal of the excavation + sloping will be added.

Also new filling sand....

Also painter costs, 3,000 EUR for spray painting; concrete absorbs....

Floor coverings; covering stairs, etc.

In total, I would rather assume 90+ THOUSAND EUR...

So no sunlight at all? How do you want to use the basement?

The guest room has a real window, the HAR, storage and bathroom manage without windows, as does the party/hobby/sports room. Only the ground floor and upper floor are permanently inhabited in this sense. The basement is "just" for guests, hobbies, parties..