Single-family new building: Planning a granny flat for future family expansion?

What exactly do you mean by [Souterrain]? Are we talking about a sloping plot with a basement used as living space?

Exactly. At the north side, ground floor height; at the south side, basement height.

OK, and from where is the access provided?

OK, and from where is the access?

Also from the north side. Here, part of the front garden could be separated as a garden for the granny flat. Entrance to the main house via external stairs to the ground floor also from the north.

I don't understand: the possible secondary apartment is in the basement, but its garden is to the north (so on the hillside one floor higher)? And why do you need a staircase to the ground floor if the secondary apartment disappears into the slope? And how do you then get to the actual garden (which would then be one floor lower on the valley side to the south)? Is there a site plan with elevations?

A shady basement apartment... imagine who would want to rent that and ask yourself if you would want someone like that as a neighbor on your property?

I don't understand: the possible granny flat is in the basement, but its garden is to the north (so on the hillside one floor higher)? And why do you need stairs to the ground floor if the granny flat disappears into the hillside? And how do you get to the main garden then (which would be one floor lower to the south on the valley side)? Is there a site plan with elevations?

The street runs from east to west in the north. The hillside rises to the south. Therefore, the garden of the granny flat is to the north at street level, the garden of the main house is one floor higher to the south.