Dimensions of Rooms for Mezuzah
A room used to live in or for storage requires a mezuzah. This includes both a storage room and a garage. However, the room must contain an area that measures at least daled al daled, four amos by four amos (approx. 1.9 meters by 1.9 meters or 6 feet by 6 feet). Even if the room doesn’t, and is, for example, slightly longer but a bit narrower—referred to in halachah as kedei lerabeia—but has the same surface area as a four by four amos area, a mezuzah is affixed, but in such a case a brachah is not recited. There is one halachic opinion that maintains that even a very small room, if it is chozi lemilsaihu, if it can fulfill its designated purpose in an area smaller than the requisite size, for example, a storage closet, it requires a mezuzah. Certainly in such a case one should not make a brachah. There are some who are stringent and follow the above-mentioned opinion that closets also need a mezuzah, but only if the closet is large enough for people to walk into.