House Extension Split-Level - The First Design

Hello everyone. We want to build an extension with a dining room and living room onto our residential building. Due to the terrain, we cannot do without a basement. Since the basement will then be "detached," we would like to possibly use it as a bedroom, etc. What have we overlooked in our plans?

Addendum: an extension is to be built here

Why split level and not an extension to the basement and ground floor at the same height?

For us, it was important to be able to access the garden on the ground floor from the new living room, hence the lowering of the living room. A basement under the living room is therefore not possible and also not necessary.

A seamless transition from the existing building to the new building is also desired. For the living room, we have an upper limitation due to an electrical line (distance 5m) that is fully utilized with this plan. The living room should have a ceiling height of 3m. This resulted in the split-level.

From the upper floor of the existing building, a roof terrace should be accessible, so the dining room height has to "approach" the ceiling height of the existing floor. ([Insulation flat roof approx. 15 - 25 cm])

Without a basement, we would have had to add a significant amount of fill, which would have required substantial foundation work or posed a risk of settlement. We decided on the basement with terrace and balcony, which at the same time enables a direct connection to the north garden.

Ok, now I get the plan. I found the "OG" a bit confusing. OG on the plan is currently your ground floor, right? And the dining area is supposed to be on that level, below that, the basement, planned for the bedroom, and the living room is in between at half height. Above the dining area is a roof terrace for the existing OG (here I’m really curious why not use the entire roof area as a terrace?)

Now I get it!

Cleverly done!
I might also consider removing the wall between the dining area and the kitchen and creating a (half) island solution for the kitchen here. Or is no new kitchen planned?

Exactly! We reduced the size of the roof terrace because of the power line. We might adjust it to the maximum size upon completion of the shell construction in coordination with the line operator. We wanted to keep the kitchen as it is. We are still considering whether to install a combined wood stove (one side for cooking, the other side for heating) between the kitchen and dining room. The problem would be the flue pipe, which would have to be laid about 3m horizontally through the kitchen to the chimney.