Cost estimation for house construction of two variants

Hello everyone, we want to build in Bochum (plot available) and would like an estimate of the costs for the following two house options:

a) 180sqm living space plus basement (white bathtub, slight slope, 1m height difference across the width of the plot), 1.5 floors, Kfw 55 or less, ventilation system, demolition of existing building with basement excluded, medium finish, ready to move in

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


We would also be interested in the approximate range of costs for purchasing materials at the building supply store. Can you also give an approximate estimate for that? Possibly just the rough share of the construction costs.

Addendum: massive, gable roof

It's a pity that no one has responded yet. Perhaps we should mention that we have received prices from both prefab house companies and architects, but we would like to hear an opinion from people who have already built.

If you have read the relevant threads here in the forum, you know that you can calculate from €1,500/sqm + basement + additional construction costs. Slope location + high energy standard do not make it cheaper for you. Are the offers actually ready for occupancy? Or "just" turnkey, which incurs further costs.

The architect ESTIMATES, the prefabricated house company also offers you a suitable reference point, although of course it depends on the company and the description of construction services. Do you think their prices are wrong and it is much cheaper elsewhere?

How come you oscillate between two such different construction types as "architect" and "prefabricated house company"? There are big differences in construction methods. Or do you mean a general contractor (GU/GÜ)?

The problem with building material trade prices is that the materials also have to be installed!

380K € + 40K € ancillary construction costs.

The prefabricated house was purely out of interest. It's about ready-to-move-in. The prices differ massively and since we have only ever heard 1500-1700 plus basement (50,000?!) so far, we were somewhat surprised by 1700 per sqm for the basement. You would come to 500,000 including additional costs plus exterior facilities and we consider that quite expensive, given that we don't have any major special requests.

Building material prices are interesting for a different reason.