Prefabricated house planning semi-detached house with budget limit

Hello,

I am new here, have already read a lot, and absorbed many tips and hints from the various threads. I would also like to ask you for advice about my house design:
We want to build a semi-detached house in a new development area in Bavaria. We have set a limit of €300,000, of which €100,000 is for the plot of land. We definitely want a basement.
To stay within budget, we want to build a prefabricated house due to the short construction period. We also want a "cost guarantee" and therefore prefer not to have an architect and individual tenders. We are currently in the process of selecting a suitable provider from the many available. Most standard offers have a utility room (HAR) on the ground floor and only 3 bedrooms in total. Because of the basement, we do not need a utility room on the ground floor; it can be in the basement. I would still like to accommodate our newly purchased washer-dryer in the shower bathroom on the ground floor so that you don’t always have to go from the basement to the garden. However, I also wish for an external basement staircase so I can bring my woodworking workshop and all other dirty stuff directly into the basement. Therefore, the washing machine could also be downstairs.

I have tried to consider the following principles:
- Concentrate sanitary facilities/piping in one place.
- "Simple geometry," it fits on the ground floor, but somehow not upstairs.
- Compact external dimensions
- Small traffic areas -> resulting in a micro-hallway upstairs. That is not nice; it could be even smaller if all doors were arranged in a pentagon. That might even be a bit refreshing, combined with differently colored doors or interesting lighting.
- Small footprint (8x9m)
- Large, continuous roof area facing south for solar energy
- Few roof windows (not shown)
- Living room to the south
- Kitchen to the north
- Staircase in the living area
- Washing machine on the ground floor

Site plan and floor plans have north at the top. It is stated on the elevations.

Plot dimensions, oriented
The surroundings -->could<-- look like this, nothing built yet. No houses, no trees.
Ground floor plan, house dimensions 8x9m, oriented
Upper floor plan, knee wall currently 1m, but will probably be smaller
ISO from southeast
South elevation
View from the east (obscured by 2nd semi-detached house)

Best regards,
Tim

Development plan/restrictions
Plot size: 323m²
Slope: yes, slightly sloping from north to south, approx. 30-50cm difference across the plot
Site coverage: 0.35
Floor area ratio: 0.7
Building window, building line and boundary: a line 3m set back from the street, setback areas according to Bavarian regulations
Edge development: semi-detached house, the second semi-detached house will be on the east side. This does not have to be identical or aligned flush.
Number of parking spaces: 2
Number of floors: II, the second full floor is only permitted in the attic.
Roof type: symmetrical gable roof
Style: no specification
Orientation: south
Maximum heights/limits: eaves side 4m, ridge height 9m
Other specifications: roof pitch 45° +/- 3°

Client requirements
Style, roof form, building type: classic
Basement, floors: basement, ground floor, upper floor
Number of people, age: 2 parents, 2-3 children
Space requirements on ground floor, upper floor:
Ground floor: living, dining, kitchen, guest, shower bathroom with washer-dryer
Upper floor: 3 bedrooms, bathroom
Basement: workshop, storage room, possibly utility room; due to the slight slope, the guest room could also be placed on the basement south side with basement windows uncovered. I grew up like that myself and it worked well for me.
Office: family use, either in guest room or bedroom
Guests per year: parents-in-law, once a month
Open or closed architecture: open
Conservative or modern construction: does not matter, main thing is cheap.
Open kitchen, cooking island: kitchen open, cooking island rather not
Number of dining seats: 5
Fireplace: no
Music/stereo wall: no
Balcony, roof terrace: no
Garage, carport: yes, min. 1x carport + 1 open parking space
Utility garden, greenhouse: currently not
Other wishes/special features/daily routine

House design
Who designed it: Do it Yourself
What is liked particularly?
- There are 5 rooms on ~130m².
- All sanitary facilities are stacked on top of each other (cost).
- The staircase is not at the entrance door. (My wife pays close attention to cleanliness, I don’t at all. We need a boundary between dirty/clean in the house.)

What is not liked?
The upper floor has not yet come out quite right:
- The "hallway" on the upper floor. Due to maximum space utilization it is a windowless micro-chamber with 4 doors.
- The children's rooms are very small at ~12m²; I would prefer them to be 2-3m³ larger at the expense of the bathroom and parents’ bedroom. But I don’t know how.
- I don’t like sloping ceilings where I can bang my head. I could get really annoyed by that.
(- The basement stairs are missing. Mentally they are located under the living room stairs.)
(- Currently no access to the attic.)

Price estimate according to architect/planner: none yet
Personal price limit for the house, including equipment: €200,000 including basement
Preferred heating technology: geothermal + solar

If you have to do without, on which details/expansions:
- can you dispense with:
any frills, anything that costs.
- can you not dispense with:
4 bedrooms, basement, 2 showers

Hello Tim, welcome to the HBF. If you have already read a lot and browsed through our forum, you can certainly guess what is lacking and where your idea falls short.

Your requirements simply cannot be realized within your cost limit.

I estimate that even without a basement, it will be tight with geothermal energy and solar (that alone already roughly approaches 30k).

from on the road

Well, that's of course annoying. But you have significantly more experience than I do, so I guess I have to think of something else. What can be done about it? Is it the layout, the size? Or is it the basement and the heating system? Edit: Thanks for your quick responses!

It's about the money! Calculate at least 1500 Euro per m2 then you'll know what you can afford. In addition, there are land costs and construction ancillary costs. With that amount, it makes more sense to buy a used property.