As per the Maimonides door requires a mezuzah if:
- the doorway leads to a room which is at least 4×4 cubits14;
- the doorway has two doorposts, one on each side (not required by Law);
- the doorway has a lintel or a protrusion from the ceiling attached to the doorposts;
- the doorway leads to a room with a ceiling (not required by Law);
- the doorway has a door (not required by Law);
- the doorway opening is at least 40 inches high and 16 inches wide;
- the doorway leads to a regular (not sacred) room;
- the doorway leads to a human (not animal) dwelling;
- the doorway leads to a clean, dignified room (not a bathroom);
- the doorway leads to a permanent dwelling (not a tent or makeshift dwelling).