Floor plan discussion: Single-family house + guest apartment as a multi-generational house on the northern slope

Is there no surveying of the property and the street?
Why do you need a [Einliegerwohnung]?
I also see that the budget is not sufficient here.
Canceling the [Einliegerwohnung] and you will come a bit closer to the budget.

It is clear that this is a plan from the [GU]. Otherwise, you would start with the property and the slope problem.

First of all, thank you very much for the many responses, I will now address some of your feedback.

The granny flat might not be suitable for a rollator. Check if a 1.5 m turning radius is maintained everywhere.

As far as I know, a wheelchair needs 1.5 m and a rollator 1.2 m, right?

Is there no survey of the property and street?
Why do you need a granny flat?
I also agree that the budget is not sufficient here.
Canceling the granny flat would bring you closer to the budget.

You can tell it’s a plan from the general contractor because otherwise you would start with the property and the slope issue.

Please no general bashing of the general contractor. As described in the original post, this is an acquaintance who kindly provided his planner to make a properly dimensioned plan from our pencil sketches, so that it would be easier for us to visualize the plan and discuss changes.
That means: The plan was created purely according to our specifications, the general contractor is not responsible for it. The general contractor will definitely not build the house. I certainly will not ask someone who is doing me a favor to also survey my property and solve my "slope problem" on the side. Especially since from my point of view the slope is not a problem, but rather an advantage (see below).

As also described in the original post, the whole thing is supposed to be a multi-generational house. The granny flat is for the grandparents. Without the granny flat, we would have to provide appropriate alternative accommodation, which would of course further reduce the budget.

Including the slope, I’d guess rather 250-300k are missing...

The price estimates here are quite far above our expectations. With that, we would be almost at 4000 €/sqm for a standard house (apart from KfW40+). Isn’t that a bit exaggerated?
What would be the major cost drivers?
From my point of view, the house can generally be built rather cheaper than usual:
The 240 sqm are a lot, but spread over 3 floors, which should be cheaper than a 240 sqm bungalow (less foundation slab, roof, etc.)
There are no expensive bay windows, cantilevers, dormers, etc.
There are only 3 bathrooms/WCs for 2 apartments, which most nowadays already have in a normal single-family house.
Because of the district heating connection, we do not need our own heating. Fortunately, the connection costs are lower than the typical costs for a heat pump, for example.

The slope, which has already been called “expensive” here, I can’t really see as a cost driver either. It’s only about 6-7% gradient on average. I’ll try to describe it more precisely:
The current natural terrain profile is such that at the highest point (the southwest corner) the terrain level is not even 1 m above the specified raw floor height of the basement. Along the south facade of the basement, the ground slopes downward. At the southeast corner of the house, the terrain is less than 0.5 m above the basement’s raw floor height. In the direction of the north, the terrain also slopes down so that along the entire north facade it is at the same level or slightly below the raw floor height. Roughly estimated, compared to a flat foundation slab on an even plot, this would mean less than 50 cubic meters of soil that need to be moved additionally. These 1-2 hours of extra excavator time surely won’t cost 50,000 €. (If it does, I’d rather take a few weeks of unpaid leave and do it by hand ;-) )
The necessary retaining wall at the terrace of the basement floor is also only 7-8 m long and about 1 m high. That can’t be very expensive either. (Otherwise I’ll just do it myself with the ugly planting rings.)
The actual slope is supposed to be backfilled later to match the street level. (But as described in the original post, these not-essential external adjustments are not part of our price estimate.) From my point of view, it is even a cost advantage that we can accommodate all spoil on our own property. This means no transport and disposal costs.
Am I wrong somewhere? Have I overlooked any cost drivers?

By the way, we have already spoken with several prefab house manufacturers about the project (without a concrete floor plan, but with a 160 sqm house + 70 sqm granny flat over 3 floors, specifications from the development plan such as KfW40+ and terrain conditions). The price was also discussed and we have never received feedback that our expectations are extremely off or that the mentioned price ranges were significantly different. The only manufacturer who said the project would be difficult under 700,000 € is comparatively a more expensive provider, who offers the possibility of a NH certification. This would dampen the additional cost through subsidies and especially the cheaper interest rates. We should get the first more concrete prices (and hopefully also planning proposals) soon.
Since not everyone here is convinced of prefab houses, we also want to request quotes for solid construction in parallel. (Preferably with an almost fitting plan to better compare.)
Actually, I was always told that with individual planning there is hardly any price difference between prefab and solid construction, which is why I did not estimate higher costs here either.

So after writing such a long novel about the costs, I have a request for you: I did not post our project here to discuss the price already (which doesn’t make much sense as long as we don’t have concrete offers).
As stated in the original post, I want to discuss the floor plan first, especially the entrance, hallway, and staircase area.
Are there any criticisms or suggestions regarding this?

1.2 is stated in the standard. I have a friend for whom it is too tight with her walker. Additionally, you are planning now, and what if it is not sufficient and, for example, a wheelchair is needed temporarily until a splint or something similar is applied. Future rentals. Apartments with wheelchair access are rare. Often the 30 cm only require brainpower.

For your clarification: A bungalow is neither more expensive nor cheaper than a single-family house, because you need fewer load-bearing walls and the structural engineering for three floors is naturally much more demanding. It balances out completely. And unfortunately, you have chosen the absolutely most expensive time to build (high interest rates and very high construction costs). I completely agree with the others: 240 m2 x €3000 per m2 = €720,000 + €100,000 incidental construction costs and at least €50,000 for the slope makes about €870,000. And that's actually a rather optimistic estimate. Because even if you don’t want to create any outdoor facilities. What about lawn, terrace, driveway, L-stones for retaining? All of that costs a lot. And the incidental construction costs are something house purchase advisors tend to forget: building application, building permit, surveying, soil report (and that can bring unpleasant surprises on a slope), tree felling work, setting up a construction road, removal of soil or necessary soil replacement, foundation slab, house connection costs (electricity, water, sewage, telephone, etc.), construction water, construction electricity, insurances. You see, that all adds up and you will end up at 900k in the end. If it turns out to be a few thousand less, you can be happy. But better to plan more than too little. We just want to warn you about that here. Because if I understand you correctly, the house is only financially feasible if the parents contribute. (Are you tearing down their house?) That means you have a double responsibility not to drive them into financial ruin (to put it drastically). That’s why the financial question is the decisive one. Because if that’s not possible, plan a new floor plan with 180 m2 right away. You should still be able to accommodate well with a clever layout of the rooms.

So with Town & Country you currently get the Flair 152 RE for 300,000 EUR in the basic equipment. However, that is not KfW40+, but only EnEV2022-compliant. If you extrapolate that to your 240m², you are already at 480,000 EUR for the house in the basic equipment. But you won't get it for that price because you don't have a standard floor plan that you can just take and submit to the building authority.

Then you want:

Garage with technical room + 25,000 EUR
Slope foundation, support, drainage + 50,000 EUR
KfW40+ instead of EnEV2022 + 50,000 EUR (I'm being conservative)
RC2 windows planned? +15,000 EUR

By now you are well over 600,000 EUR, but you still have no house connection, no construction period interest, no garden (somehow you will have to fence it in soon), no interior fittings...
Just for the 2 kitchens you can easily calculate 25,000 EUR. Painter 20,000, floors 20,000.

Topic granny flat:
You say for the grandparents. Do they need a 12m² office?
Does it have to be a garage? The roof terrace in the south is enough, why would you want one in the east as well?
10m² for the technical room, but washer and dryer stand in the main bathroom? The main bathroom is large for my taste, but still awkwardly shaped.
Large gallery, but no possibility to put a closet.
15m² study room is generous too. If you both work from home... that won't work in one shared room anyway...
Pantry 7m²... 21,000 EUR for a storage closet, although you have a 10m² utility room AND a fairly large kitchen...
I would also leave out the shower in the guest WC. Guests go to the main bathroom anyway, since it is upstairs...
I also find the guest room pointless, but that's a matter of taste. The 10m³ cost 30,000 EUR plus interest. For that it stands empty 90% of the year and needs heating.

180m² I don't find realistic with a granny flat if a study room is necessary because you work from home. But you could compress it into 200m². It will still be tight because you insist on the granny flat.
Without it you would come to 150-160m², then it would be realistic.

PS:
I also don't see the slope in your drawings. If the terrain rises 2m from NE to SW, then the living room of the granny flat is almost completely underground. How is a terrace supposed to be built there? How are windows supposed to go there? Especially since there is a balcony directly above to the south. It will be dark as in a bag there.

Please no general GU-bashing. As described in the initial post, this is an acquaintance who kindly provided his planner to turn our pencil drawings into a properly dimensioned plan, so that it is easier for us to imagine the plan and discuss changes. That means: the plan was created purely according to our specifications, the GU is not responsible for it. The GU will definitely not build the house. I certainly will not demand from someone who is kindly doing me a favor to just measure my property on the side and solve my "slope problem." Especially since from my point of view the slope is not a problem, but rather has advantages. (see below)

As also described in the initial post, the whole thing is supposed to be a multi-generational house. The granny flat is for the grandparents. Without the granny flat, we would have to provide appropriate replacement, which would of course reduce the budget accordingly.

I have no intention of criticizing the GU planner here. It's just that the basics are missing, the planner can't invent those. Surveying is the keyword. You can't avoid that anyway. So there is no surveying yet. How can you say anything about the design then?

Your description of the slope is all well and good, but the planner's language is the plan. Then just take the data from the geoportal. That is accurate enough for the overview.