Comment by Netch

> find the convention used in many countries of numbering building floors starting with zero to be more logical.

Ukrainian here. Multi-floor buildings always have at least one stair section to first floor due to need of thermal basement isolation. (I guess this is not pertaining to Western Europe due to more clement winters.) And, yep, it is called "first" floor. Using zero number is rare but possible (in this case it is called "tsokolny" floor) if a real "basement floor" is present, but in this case still 1-based numbering is preferred.