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.

We have a cost estimate for a house with basic dimensions of 9.80m x 12.30m (32.2 ft x 40.4 ft), knee wall height 2.25m (7.4 ft).

Plus a basement with usable space and a double garage 6.0m x 7.0m (19.7 ft x 23.0 ft) at around 580,000 EURO all-inclusive.
However, we have also planned an expensive large terrace roof.

Garden costs are not included.

So your costs of 600,000 euros are quite realistic.

10 by 12 meters (approximately 39 by 39 feet) in external dimensions do not equal 120 square meters (approximately 1,292 square feet) of living space. You can safely subtract about 20% for exterior and interior walls.
A basement costs money; a livable basement requires additional insulation, heating, possibly ventilation, and larger windows, among other things.
Still, the costs seem to be estimated on the higher side – are you planning to build by contracting individual trades or using a general contractor?

Good evening,

MarcWen schrieb:

Plan to build a single-family house, 1.5 stories, footprint approximately 10 x 12 meters (knee wall about 1 meter (3 feet))

• KfW 55 standard
• If I roughly calculate, the ground floor and upper floor together come to about 210 sqm (square meters) (2260 sq ft) of living space
• Move-in ready
• Now I take this conceptual single-family house and instead of building on a slab foundation, I plan a basement with around 75 sqm (square meters) (807 sq ft) of living space below (remaining area used as utility space)
• We complete our dream with a double garage including a walkable roof terrace

A rough estimate would be closer to 180 sqm (1937 sq ft), depending on the proportion of walls.

Single-family house, KfW 70 approx.: EUR 281,000 (including ventilation and turnkey)
Utility basement approx.: EUR 47,000
Conversion to living basement approx.: EUR 35,000 (including shower bathroom)
Additional cost for KfW 55 approx.: EUR 10,000
Double garage as a prefabricated garage approx.: EUR 13,000
with walkable roof terrace, about 50% more (although the question is whether it will be used)
Painting work/floor coverings approx.: EUR 45,000
Reserve for extras: EUR 10,000
Typical additional building costs: EUR 40,000

Total approx. EUR 487,500

MarcWen schrieb:

• Sometimes costs are calculated twice; the living basement costs a total fixed sum, plus costs per sqm of living space
• If you project the ground floor downwards, 120 sqm (1292 sq ft) at 2,000 Euro/sqm, 200,000 Euro
• The living basement is basically like a separate house, like a bungalow, so it costs approx. 250,000 Euro

I would have laughed out loud, shown the consultant the door, or if the discussions took place at the provider’s office, just left.

MarcWen schrieb:

Then the house costs 600,000+ Euro and I have the feeling we are planning our living basement more as a cash cow for the builder.

Depending on where the plot is located and how much it costs, you won’t make it with that budget!

But it is true that a living basement is an expensive undertaking, as you can see above. If the soil analysis comes back unfavorable, costs in the five-figure range can be added.

All in all, your previous “experiences” with consultants do not sound very promising. My suggestion: write it off as a learning experience and look for a reputable provider.

Regards, Bauexperte

Good evening,

Baufie schrieb:

So your costs of 600,000 euros are about right.

No.

NRW is already expensive – recently construction prices have increased; however, it’s still not as expensive as BW or Bavaria.

Regards, Bauexperte

You are mistaken about your living area – we have the same dimensions and come to 165 sqm (1,776 sq ft) on the ground floor/first floor, but the utility room was counted as usable space (12 sqm / 129 sq ft more). We also have a knee wall of 1.25 m (4 ft) and two bay windows.

Our basement has three heated rooms plus the hallway, adding up to just over 50 sqm (538 sq ft) of living space.

For a basement with standard waterproofing, I would normally estimate around 60,000 euros.

600,000 euros for that size and a standard finish? That would be unbelievable to me.