The foundational rule, established already in the Gemara (Yoma 11a) and codified by the Rambam (Mishneh Torah, Mezuzah 6:7–8), is that the mezuzah obligation follows the criterion of dwelling (dirat keva): spaces set aside for human habitation or use require a mezuzah, while areas serving merely as passageways—gatehouse entrances, porches, gardens—are exempt on their own, though they become obligated when dwellings open into them.
A jointly owned house is explicitly obligated in mezuzah, as the Gemara (Yoma 11b) derives from the verse 'למען ירבו ימיכם,' ruling that partnership ownership creates no exemption—a point reiterated by the Rambam (Mishneh Torah, Mezuzah 6:12) and the Tur (Tur, Yoreh De'ah 286), who list a 'beit hashutafin' explicitly among obligated structures.
The obligation extends beyond formal residences to any space put to meaningful human use: Arukh HaShulchan (Yoreh De'ah 286:2–5) rules that even storehouses for wine, oil, or merchandise are obligated because the owner makes regular use of them, and even where non-Jewish servants do the actual handling the space is still considered the owner's domain.
Conversely, a space of disrepute or degradation—a bathhouse, latrine, or tannery—is exempt, as Arukh HaShulchan (Yoreh De'ah 286:5) explains: such spaces are not 'dirat kavod,' and it would be dishonorable to the Divine Name to place a mezuzah there.
Applying these principles to a shared building lobby, Iggerot Moshe (Yoreh De'ah 1:181) addresses the halachic status of shared courtyard and entrance spaces, analyzing whether the doorways to courtyards, gardens, and multi-use passages are obligated based on whether a dwelling opens into them and the nature of passage through them.
B'tzel HaChochma (5:157) examines directly whether a common stairwell in a building with both Jewish and non-Jewish tenants requires a mezuzah, working through partnership law, the distinction between ownership-based and usage-based obligations, and the effect of the majority-minority composition of tenants on the shared space's status.
Teshuvos V'hanhagos (2:548) addresses the status of an intermediate hallway (gazoztra) leading from an exempt space such as a bathhouse, concluding that if such a hallway functions as a dwelling space of at least four by four cubits it may require a mezuzah, though given the uncertainty the author leans toward affixing one without a blessing.
Minchas Yitzchak (4:89) engages with the broader category of spaces used intermittently by visitors or non-residents—such as a bathhouse entrance—and concludes that in practice a mezuzah should be affixed without a blessing when the space does not clearly meet the criteria of a permanent dwelling.
Revavos Ephraim (2:29) addresses the blessing recited when affixing a mezuzah in a shared structure, analyzing whether the resident or an agent should recite the brachah, drawing on the Rambam's distinction between affixing for oneself and affixing on behalf of others.
Maayan Omer (2:6:22) addresses a shared building entrance and finds no fundamental halachic prohibition against treating it as obligated, noting that all residents share common use of the communal space, and references a related responsum in Yabbia Omer on the matter.
Responsa on this question
Tzitz Eliezer (Tzitz Eliezer 12:59) — Tzitz Eliezer (12:59) addresses whether a son may restrain his mentally disturbed mother by tying her to a chair per medical instruction, and rules that he must instead entrust her care to others to manage her as necessary according to her condition and medical directive, rather than performing such physical restraint himself.
B'tzel HaChochma (B'tzel HaChochma 3:80) — B'tzel HaChochma rules that an elevator is exempt from the requirement of a mezuzah even when it has two doorways opposite each other and serves as an entryway to a fixed dwelling, because an elevator is not permanently affixed in place and constantly moves up and down, thereby losing its character as a gatehouse at all times.
B'tzel HaChochma (B'tzel HaChochma 3:81) — B'tzel HaChochma (3:81) rules that the doors of an elevator and the doors built on each floor through which one enters and exits the elevator are exempt from mezuzah, because the elevator is not a permanent dwelling—it continuously moves between floors and lacks the fixed entrance and exit characteristic of a space obligated in mezuzah.
B'tzel HaChochma (B'tzel HaChochma 3:82) — B'tzel HaChochma (3:82) rules that an elevator is exempt from the requirement of a mezuzah because it lacks a fixed dwelling place, as it is not permanently stationed in one location.
B'tzel HaChochma (B'tzel HaChochma 3:83) — B'tzel HaChochma rules that a house on a ship is exempt from the requirement of a mezuzah because a ship is not designed as a permanent dwelling but rather for transporting people and goods from one place to another.
