Semi-detached house in building area 8.5m x 15m (WxD)

A thank you is certainly sufficient. The best way to express gratitude is by answering questions and providing more information. For that, a thank you from me as well.

For me, thanks work via Paypal.

Also good. Amazon vouchers are also not bad.

Well, there are quite a few houses with <50 sqm living space on the ground floor and 6 rooms. Only they are not square – and have more than just 2 floors like the usual "city villa"

I didn’t say that either. Only you have this kind of consistent limitation.

Half a million.

Oh wow!

None of those is our wish. All that probably would have been produced by the floor plan form. But we are not there yet...

You, you would be the first one who after a lot of brainpower wouldn’t say that actually „one wants it differently“. Usually it is the woman who is blamed.

Looks very exciting, but I don’t quite understand yet. Two-story basement + upper floor (garden level) + 2nd upper floor. Flat roof is not possible, so another attic on top? Where is the dividing line between the two living units now?

The dividing line is bluntly in the middle. Garden level 1st living unit on the ground floor south, garden level 2nd living unit in the "upper floor" north, which would basically be the upper upper floor for the 2nd living unit. You can tell by the side entrance door.
The third floor (for the 2nd living unit the second) I have created just bluntly without windows, roof initially not at all. Because it also all costs time..
This is definitely about the shares for both living units.

2 floors so approx. 90–96 sqm plus attic would be the result of @hanghaus2023 study in and then one still has to

I have another suggestion, based on mine: the southern living unit gets the basement on the ground floor level and pulls the rooms including the light well in the slope a bit there. The northern living unit gets the attic, meaning the visible third under the roof. Then each would have 1 1/2 floors of the two-family house. If you can actually pay for that, then the 3rd attic floor is still an option.

The concept is also to retreat to a separate floor for the home office, as far away as possible from the hustle and bustle on the ground floor.

In maisonettes EG/UG and OG/DG, for example.

All of this would probably have produced the floor plan form. But we’re not there yet...

Which floor plan form?

It is not set in stone that the two semi-detached halves have to be completely identical.

They wouldn’t be able to here either. However, you have not yet given any indication of what deviations the room programs would have. I am still completely unclear about what the concept looks like: You bought the plot, and the friendly family are only creditors of a vague two-party building idea and get a surprise half? – Yvonne has already hinted that a gap between expectation and result could develop into a breaking point. Do you really have the mandate that the extremes "unfortunately, there was no room left for you" or "you get the uglier half, but at least it’s cheaper" may come out for the friends?

The property allows 127 m² of floor area and 3 full floors (+attic +possibly basement). That then makes something between 400 and 500 m² of floor space – which is more than enough for 2 families with a total of 4 home offices.

127 sqm of floor area that may be built on (15*8.5) does not lead to 400 to 500 sqm of living space, but only up to 48 sqm of living space per floor for each housing unit.

... how would you arrange the two garages and also one parking space each for those side entrances from ? I don’t see how that could work. There is simply no space in the 6 m area from the street to the start of the building zone.

Hello everyone,
I have received a lot of input here that I first had to work through. Meanwhile, the plans have further developed because of this – and new questions have also arisen. Now I will address yours first.

I even sketched that first. But I’m not sure if the base height doesn’t argue against it. In any case, it’s an approach.

How is the base height defined on a slope? In other contexts, the height is usually the average height of the slope. But that makes little sense for the base, because then the base at the upper end of the slope would disappear into the ground.

At worst, probably also an asymmetrical gable roof with the ridge over the rear half (and in a way a shed roof over the front), in order to be able to set the rear one story higher...

Very exciting idea! What is allowed with SD 35-45°?
Different roof pitches on both sides?
Offset shed roof?
Same pitch, but ridge not centered?

That then makes something between 400 and 500 m² floor area – which is more than enough for 2 families with a total of 4 home offices.

127 sqm base area that may be built on (15*8.5) does not lead to 400 to 500 sqm living area, but rather max. 48 sqm living area per floor per residential unit.

Wait, I was talking about the floor area of the entire house and you are talking about living area per floor per residential unit. That is an apples-to-oranges comparison – and not even a contradiction to my statement. What were you trying to get at?

Wait, I was talking about the total floor area of the entire house and you about the living area per floor per residential unit. That’s comparing apples and oranges – and not even a contradiction to my statement. What point were you trying to make?

127 sqm building envelope for 2 halves of a semi-detached house.
Based on the design by , that means per semi-detached house, i.e. per residential unit: outside 7.5*8.5m.
If you then subtract the exterior and interior walls, about 48 sqm of living space remains per floor. 3 floors then equal about 144 sqm for 2 semi-detached houses, so around 288 sqm, thus under 300 sqm of living space.
That was in response to

That then makes something between 400 and 500 sqm of floor area – which is more than enough for 2 families with a total of 4 home offices.

which implies a lot of living space and should be illustrated realistically with normal house floor plans.

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