We take after the British way rather than the American way.
On an elevator, ground floors can be marked two ways. Either "0" or "Z" which stands for "Zemin-Ground" floor. However if you live on the ground floor of a building, you wouldn't refer to it as "0. Kat", you'd either say "giriş kat-entrance floor" or "zemin kat-ground floor".
I certainly had no clue about this back when I first moved to America so it's a great question to ask! :)
"Çünkü 13 sayısı (or rakamı) uğursuz". :) Just a little friendly correction. We don't say "sayı 13, sayı 1" etc. like in English and many other languages. Also "şanssız" is used for unfortunate people or maybe animals.. For things and people who bring bad luck, we use "uğursuz".