425. Not Respectable Dwellings; Rooms Within Rooms
Tefillin, Mezuzah v’Sefer Torah 6:9
A restroom, a bathhouse, a mikvah, a tannery, and similar such buildings do not require a mezuzah because they are not respectable dwellings. A sukkah and a house on a boat do not require a mezuzah because they are not permanent dwellings. If a potter has two booths, one inside the other, the outer booth does not require a mezuzah because it is only a temporary structure. Shops in the marketplace do not require a mezuzah because they are not permanent dwellings.
Tefillin, Mezuzah v’Sefer Torah 6:10
A building with many doorways requires a mezuzah for every one of them even if one typically uses only one of them. The small passageway between a house and its attic requires a mezuzah. A room in a house, even a room that leads to another room, requires a mezuzah on the innermost room, the outer room, and the house, because all of them are permanent structures used for dwelling.