Cost estimation for house construction of two variants

Well, for example, you are building a basement at b - that is expensive!
Besides, the house is not exactly small.
On top of that, you have many special requests: Kfw 55 or better, demolition, hillside location, basement or cellar, move-in ready instead of turnkey. Outdoor facilities are also expensive, quickly €50,000 are gone.

Well, with 180 sqm it would be a completely normal basement, so we don't know where the approximately threefold price is supposed to come from. And if you put 30 sqm downstairs, apart from windows not much else would really have to be done plus you save 30 sqm upstairs...

Good evening,

a) 180sqm living space plus basement (white bathtub, slight hillside, 1m height difference across the property width), 1.5 floors, KfW 55 or less, ventilation system, demolition of old building with basement excluded, medium equipment, ready to move in

Demolition costs depend on when the existing property was originally built, which materials were used, and how large it is. You should ask a demolition contractor for an offer here.

Single-family house 180 sqm, insulated basement: TEUR 280
Utility basement: TEUR 50
Controlled residential ventilation with heat recovery: TEUR 12
Surcharge KfW 55: TEUR 13
Painting/floor coverings in EL: TEUR 20
Outdoor facilities: TEUR 10 (only the essentials)
Reserves extras: TEUR 10
Additional construction costs: TEUR 30

All in _before land: TEUR 425 plus costs for plaster on exposed basement masonry according to measurement.

b) 150sqm living space plus basement with two offices (basement level), rest see a)

Single-family house 150 sqm, insulated basement: TEUR 240
Utility basement: TEUR 42
Finished living basement total: TEUR 20 (incl. floor height increase; half expansion makes no sense)
Controlled residential ventilation with heat recovery: TEUR 12
Surcharge KfW 55: TEUR 12
Painting/floor coverings in EL: TEUR 20
Outdoor facilities: TEUR 10 (only the essentials)
Reserves extras: TEUR 10
Additional construction costs: TEUR 30

All in _before land: TEUR 396 plus costs for plaster on exposed basement masonry according to measurement.

Furthermore, we would be interested in the approximate amount you would need to purchase at the building materials trade. Can you also give a rough estimate there? Possibly just the rough share of the construction costs.

Not at all when awarding via general contractor.

Best regards from the Rhineland

I didn't guess that badly at all :D