Shed roof 20 degrees - without attic?

If you don't build basements, you still need an attic. The stuff that you only need twice a year has to go somewhere.

With a house width of 8 meters, you already have a height difference of 290 cm between ridge and eaves, or 360 cm at 10 meters.

Exactly.

The tangent of 20 degrees is 0.36. Therefore, he can determine the ceiling height for any desired house depth himself.
You can also vary the wall starting height. Instead of starting directly with 2.5 m, maybe with 1.8 m. Of course, this strongly depends on the floor plan! ;)

We are planning a semi-detached house in the new development area.

I strongly advise against planning semi-detached houses individually. I recommend you google "A semi-detached house has TWO halves" and read the thread , whose OP emphasizes stating that it should not be recommended solely as a horror story while praising his general contractor, who manages to perform well amid all the mayoral and neighborly disasters :)

2 full floors are required (attic optional) and a 20-degree pitched shed roof.

I assume you are only giving a very shortened version of your development plan here. Moreover, some roofing materials are only recommended starting at 21 or 22 degrees roof pitch; 20° RP can therefore narrowly be limited to zinc sheet. Whether you have to calculate the pitch all the way to the other end of the house depends on whether a recessed story is possible.

Developer not yet decided,

Then you probably mean a general contractor. You could not choose a developer, but then you would not need to think further about the house. At least find the planner together with your neighbor; this does not exclude different houses or different building methods, see also the aforementioned post online. Do not build as if each one had a property with boundary clearances on all sides individually planned, and all the less so individually planned with the no-basement dwelling in front of the basement dwelling, see the Goalkeeper thread.

to read, whose original poster @goalkeeper emphasizes the point that it is not to be recommended merely as a horror story without praising his general contractor, who makes a good impression amidst all the mayoral and neighborly disasters :)

Hear, hear!!

However, I must point out that with a reasonable and already existing neighbor, you can also build two separate houses. Our neighbors – a total of ten semi-detached houses – all had different construction companies. Partly prefabricated and solid houses side by side.

As long as the miserable issue with the foundation is settled, the rest is basically a formality – at least with reasonable people. :rolleyes:

If you don't build basements, you need an attic. You need somewhere to put all the stuff you only use twice a year.

Well, whether you need that is debatable, you have a utility room for that. Quite a few people already know without a basement and attic ... ;)

Well, whether you need that is another matter, after all you have a utility room. I know quite a few people without a basement and attic ... ;)

The biggest trap in house building (I learned here, and am happy to have followed it) is underestimating the storage space needed. Suitcases, Christmas decorations, etc... the utility room then really has to be large.