The Ten Commandments of Mezuzah

The laws governing where one places a mezuzah are, indeed, complicated. The Rambam (Hilchos Mezuzah 6:1) codifies ten necessary requirements that must be fulfilled for a house or room to be obligated to have a mezuzah. Of course, there is disagreement regarding particular circumstances.

This is the general rule that is applied for any case when there is a safek whether one must install a mezuzah. One does not recite a beracha, but it is optimal to place this mezuzah immediately after putting up a different mezuzah that requires a beracha, thereby including the safek situation with the beracha.

1. The room must have a minimum area of four amos by four amos (which is about fifty square feet). In the Rambam’s opinion, it is not necessary that each side be at least four amos wide – if the room or building’s area is at least sixteen square amos, one must place a mezuzah on its entrance. Thus, according to the Rambam’s opinion, a room that is three amos wide and six amos long requires a mezuzah.
2. The entrance must have side-posts on both sides.
3. The entrance must have a mashkof, that is, something that comes down vertically, similar to the way a lintel functions as the top of a doorway.
4. The room or house must be roofed. An enclosed yard or porch without a roof does not require a mezuzah, although sometimes the doorway to an unroofed yard or porch functions as an entrance to the house and requires a mezuzah for this reason. However, a doorway of an unroofed room or building that is not an entranceway to a house does not need a mezuzah.
5. In the Rambam’s opinion, a mezuzah is required only when the house or room’s entrance has a door. In this instance, the Rambam’s position is a minority opinion, since most other Rishonim contend that the lack of a door does not absolve the requirement of a mezuzah. The accepted conclusion is to install a mezuzah in a doorway that has no door, but not to recite a beracha when doing so (Shulchan Aruch, Yoreh Deah 286:15). (Again, the best option here is to place this mezuzah immediately after putting up a mezuzah in a place that all opinions require one, with the beracha recited on the latter mezuzah.)
6. The sideposts of the entrance are at least ten tefachim tall, which is between 32 and 38 inches.
7. The house or room does not have the sanctity of a shul or beis medrash. In the Rambam’s opinion, a beis medrash does not require a mezuzah. Most authorities rule that one should place a mezuzah on a beis medrash, and, therefore, accepted practice is to place a mezuzah on any beis medrash, but without a beracha. Common practice today is to treat a shul as a beis medrash and, therefore, to place a mezuzah on its door without a beracha.
8. The house or room is intended for human habitation. For example, stables and barns are absolved of the requirement of mezuzah.
9. The house or room is meant for an honorable use, as opposed to a bathroom or similar rooms, where we do not install a mezuzah.
10. The room or house is intended for permanent use. For this reason, we do not install a mezuzah on a sukkah.