Don’t you see how that’s such an obviously ugly and mathematically unsatisfying retrofit to make your shit work?
B2 B1 1 2 3
vs
-2 -1 0 1 2
And what the hell do you even do in a situation where 0 is at street level but -1 opens on a backyard or something. It’s clearly not a basement, but it’s clearly not the ground floor either.
Or do you never build an elevator in such buildings in order not to trigger massive cognitive dissonance?
EDIT: Holy shit there is another layer to this hypocrisy cake. Americans swear up and down that they have to write “12/11” because they say “12th of September”, but their floor notation is literally “B1” for “First Basement”. Clearly the only rule they follow is that they’ll do whatever is least logical and convenient just to piss off everyone who is forced to work with them.
Main entrance determines the position of the ground floor. If your basement leads to a backyard that leads to another street, it’s just a basement access.
Unless you declare the basement entrance to be the main entrance, then the initial ground level entrance is not on the ground floor anymore. So it’s pretty much up to your discretion how you handle it.
In some buildings the backyard level has windows though. It’s clearly not a basement, just a (partially or mostly) above-ground floor that happens not to be at street level.
Furthermore French for “ground floor” literally translates to “street level” so going by linguistics we can’t declare any other level to be the ground floor to make whatever “B1” is work consistently.
