Floor plan design city villa with basement improvement suggestion?

Since we have a slight slope, the basement with the granny flat was a good option here.

That’s why I thought the basement was supposed to be a separate living unit? In that case, it should also be appropriately equipped (bathroom, washer/dryer, kitchen, ...) and the stairs should be decoupled accordingly from the upper area.

That's why I thought the basement was supposed to represent a separate living unit? Then it should also be appropriately equipped (bathroom, washer/dryer, kitchen,...) and the stairs should be decoupled from the upper area accordingly.

After careful consideration, a separate living unit is the better solution but also the more expensive option....

Yes, after careful consideration, a separate residential unit is the better solution but also the more expensive option....

What should be more expensive there than in the current plan? You just have to either leave out the basement stairs or make them lockable with a door. That doesn't cost a lot.

...or make it lockable with a door.

But there is a door that could be locked. Or am I mistaken?

Yes d

But there is a door that can be locked. Or am I mistaken?

Yes, there is a door that can be locked..

I meant with the costs that the shower on the upper floor (guest WC) would be cheaper compared to the bathroom in the basement, but the shower & WC belong in the rooms where people spend time, so we will accept the additional costs and have the bathroom installed in the basement.

That can also happen to you with external site management.

Yes, even with an architect, if he is not connected on site.