ᐅ Single-Family Home Construction Plan: Key Issue – Basement Living Space, Dream or Nightmare

Dear forum members, we need some support. To possibly take some concerns off our minds or to gather more courage. For about four weeks now, we have been going in circles without making real progress.

Without going into too much detail, it should be possible to provide a realistic assessment of whether our project is feasible:

• Plan for a one-and-a-half-story single-family house, footprint approximately 10 x 12 meters (knee wall about 1 meter)
• KFW 55 standard
• If I roughly calculate, the ground floor and upper floor together add up to about 210 sqm (2,260 sq ft) of living space
• Move-in ready construction
• Now I take this hypothetical single-family house and instead of building on a concrete slab, plan a basement with about 75 sqm (810 sq ft) of living space (rest as usable space)
• We complete our dream with a double garage including a walkable roof terrace

We are leaving out landscaping and so on. Otherwise, no major frills or anything like that planned. Room and floor layouts are practical and functional. For example, there is only one bathroom per floor (~10 sqm (110 sq ft), so no wellness area or cost drivers). The house type also does not include many extras at this stage—no bay windows, balconies, many windows, etc., just a simple gable roof on top.

Of course, I could now calculate the 210 sqm (2,260 sq ft) of living space at the commonly quoted rate of 2,000 euros per sqm + garage + basement.

The sticking point is always this living basement. Everyone seems to struggle with it, or we haven’t found the right builder yet. At the beginning, we looked at some online sources and roughly budgeted around 60,000 euros. However, the feedback from our current contacts is mostly just a dismissive smile. Some of the estimates even made me hold back laughter:

• Sometimes costs are double-counted; the living basement costs a total sum x, plus cost per sqm of living space
• The ground floor is projected downward: 120 sqm (1,290 sq ft) x 2,000 euros per sqm, totaling 200,000 euros
• The living basement is almost like a separate house or bungalow, so it costs about 250,000 euros

Surely, the truth lies somewhere in between, but what would be realistic? Unfortunately, conversations usually fail at this point, with the question of what else to consider or revise. Then the house ends up costing 600,000+ euros, and I have the uneasy feeling that we are planning our living basement more as a goldmine for the builder.