ᐅ Sacrifice a basement to gain 20m² of additional living space?

Hello,

we are still in a very early stage of our building project.
-> Idea collection; about 2–3 years before construction starts
That’s why I have already been actively reading in this forum.

Now about us...

As I sketch my wife’s special requests on paper, I realize more and more that the living space planned so far will not be enough. My wife wants the following rooms on the upper floor:

- 2 children’s bedrooms (about 14.5 m² (156 sq ft))
- 1 bathroom for the children (about 6 m² (65 sq ft))
- 1 master bedroom (about 14 m² (151 sq ft))
- 1 walk-in closet (about 7 m² (75 sq ft); adjacent to the master bedroom)
- 1 bathroom (about 11 m² (118 sq ft); adjacent to the master bedroom)
- Hallway (about 6 m² (65 sq ft))
- Staircase (about 2 m² (22 sq ft))

Last week we visited a prefabricated house center and looked at similar floor plans (the size of the rooms). It became increasingly clear to me that 150–160 m² (1,615–1,722 sq ft) would be very tight because the rooms tend to be rather small. Also, because of the large upper floor plus the planned basement, we have quite a lot of space that can be freely distributed.

My idea is therefore to skip the basement and increase the living area to about 180 m² (1,938 sq ft). We could definitely use the extra 10 m² (108 sq ft) on the upper floor, and it would also be necessary downstairs for the technical rooms.

My question now is how this would affect the cost of our building project?

Previous plan: 160 m² (1,722 sq ft) + 70 m² (753 sq ft) basement
New plan: 180 m² (1,938 sq ft) without basement

Is it possible to estimate this roughly?
Thank you very much for your help!