Two-family house new construction - Which costs to calculate?

Therefore, many of these floor plans for so-called multigenerational houses are rather such that there is an apartment for the older generation on the lower level and on this level also a part of the apartment for the younger generation.

For example, I could imagine the parents' apartment being about 80 to 90 sqm, plus a kitchen/dining area for the younger generation with direct garden access and a guest WC also on the ground floor (about 40 to 50 sqm due to the stairs). On the upper floor then a cozy smaller living area, bedroom, bathroom, study above everything.
Ideally a basement for laundry room, technical equipment, etc. .. in hillside solutions (also slight slopes) perhaps with a (partially) integrated garage.

That would of course also be an interesting option. Although that would then be quite large and therefore expensive. 90+50m² would be 140m² on the ground floor and the same again on the upper floor. Plus the basement.

What do the experts think, what would that cost? Would we reach the 356T€ proposed by Bauexperte, plus the basement?

Without a basement, I could also imagine 160m² of floor space, of which 100m² for the parents and 30m² for the utility room for both together - or divided again. Then there would again be 150m² available on the upper floor for the "younger generation", with the study then in the attic or on the ground floor.

Without a basement, however, I fear we won’t be able to accommodate all my parents' stuff (handicrafts without end).

You have now added both of my maximum values. What kind of rooms do your parents need? 80 sqm would already be a good size - wouldn't it?

And, sorting out is necessary before a move.

Hello,

I like to try to give you a little push, but it’s starting to reach a point where you should consult a professional construction advisor – it can also be an initial meeting with an architect. That will get you further than groping around in the “nebulous.”

You mentioned some numbers a few posts ago; if I add up everything discussed afterward without a basement, I estimate about 630,000€ (for the "side-by-side" building method). Where would we end up with a basement?

For "side-by-side," you have to calculate about EUR 95,000 for a usable basement – it lies under both residential units; including insulation of the HVAC room in the basement.

So if I keep the footprint as small as possible (100m²), the parents’ utility room would have to go into a basement. Or is it cheaper to forgo the basement and instead have about 20m² more floor space for a utility room?

100 sqm footprint corresponds to roughly 76 sqm living space.

It is always a matter of balancing what is desired with the budget. For example, a single-story annex can also be used as a utility room; if planned cleverly, there might even be space left for a cloakroom or vestibule.

That’s why I suggest you start consulting. Additionally, you can visit show home parks in your area to get a feel for the rooms and ideas; have initial conversations. As long as here a new question follows the last answer – because it sparks a new idea AND no clear direction is yet visible, it is on the one hand impossible to manage this in a forum; on the other hand, it doesn’t really get you anywhere. Nothing can replace a personal conversation.

Best regards from the Rhineland

We currently have similar thoughts:
- Basement apartment with approx. 75 sqm for parents-in-law, barrier-free
- Ground floor with at least 100 sqm living space (for us, including bedroom and office), barrier-free
- Attic with children’s and guest rooms and a granny flat

From personal experience (if this becomes concrete for you and the financing is clarified) you should find an architect. 3 WEH mean residential building class 3. Additionally, it feels like 90% of development plans restrict the maximum number of WEH to 2.

3 WEH ...

How do you come to the conclusion that the OP has 3 residential units? Apartment for parents-in-law and apartment for OP make 2 residential units for me ... and these are allowed by the vast majority of development plans; as you correctly stated Rhenish greetings