Mezuza on Back Door

Question: Our patio door leads onto our back garden and can only be opened from the inside. Which side should we affix the mezuza to?

Answer: The Gemara (Yuma 11b) teaches that one must affix the mezuza to the right-hand side of the house as one enters. The Shulchan Aruch (YD 289:2) writes that if one puts up the mezuza on the wrong side then they have not fulfilled the mitzva.

The Beis Yosef (YD 289:10) and the Taz (YD 289:4) quote the Maharil (94) who writes that if a door opens onto a courtyard that in turn opens onto the street, one places the mezuza on the right side of the doorway into which the door swings (heker tzir).

Nonetheless, the Chelkas Yaakov (YD 161) quotes the Levush who writes that we place the mezuza on the right side of the door going into the house, regardless of which way the door opens. R’ Meir Posner (Beis Meir YD 289:3) explains that as the garden itself is not obligated to have a mezuza, one must attach it onto the entrance to the house rather than on the entrance to the garden. Likewise, the Chazon Ish (YD 168:5) and R’ Moshe Feinstein (Igros Moshe YD 1:181) write that one places the mezuza on the right-hand side entrance to the house.

There is a machlokes, however, as to which side of the door the mezuza goes on when such a door opens out onto an enclosed balcony or garden. The Chazon Ish (YD 168:5) writes that any outside door is still considered to be an entrance to the house. As gardens and small balconies are not obligated with a mezuza, one must always place it on the outside going into the house.

However, R’ Chaim Elazar Spira (Minchas Elazar 2:40), R’ Moshe Feinstein, R’ Yitzchok Yaakov Weiss (Minchas Yitzchak 1:8) and R’ Ovadia Yosef (Yechave Daas 4:51) write that as the balcony or garden is only accessible from the house, the mezuza must be placed on the right side from the inside.

In conclusion, if the garden can only be accessed from the house, the mezuza should be placed on the right side from the inside. If the garden can also be accessed from the street, then the mezuza should be placed on the right side going into the house from the outside. This applies equally to patio doors, regardless of where they can be opened from.