5 points
*
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.
1 point
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.
