A few mezuzua questions:
a) If there is a staircase with a door frame at the bottom of the steps Does one need a mezuza. I technically use the staircase but I only rent the top floor of the apartment, so the staircase is really shared by me and my downstairs neighbor? The electricity for the staircase is paid by the downstairs neighbor.
b) I have an interesting situation in between my dining room and kithcen. One wall comes out around a foot (like a normal wall and then there is a gap and then the other side isn’t a standard wall. It is more like a huge box that protrudes from the wall that is around 3 to 4 feet wide. There is no mashkof on top just the ceiling. Does that need a mezuza?
a) A doorway to a staricase requires a mezuzah, because this is the way you enter your house through (Yoreh De’ah 286:1).
b) It appears that there is no obligation of a mezuzah in this case. A mezuzah is only required where there is a mashkof (287:1), and although a ceiling that ends at the doorway might be considered a mashkof (Chazon Ish 172), where the ceiling is continuous there is certainly no obligation of mezuzah.