There is a positive commandment to set up a mezuzah on every doorpost.  The details as to which doorways, how the mezuzah should be placed, and the bracha are described below.
- 1 Which doorposts require a mezuzah
- 2 Doorway in a Room
- 3 How the mezuzah should be placed
- 4 Having one's Mezuzot checked
- 5 The Bracha on putting up a Mezuzah
- 6 Rentals
- 7 Proper behavior when passing a mezuzah
- 8 Women
- 9 Children
- 10 Links
- 11 Sources
Which doorposts require a mezuzah
- Every doorway of one's house is obligated in mezuzah. Even if a room has several doorways, each one is obligated in having a mezuzah, unless a room has one doorway that is used for entering and exiting and one entrances that isn't used for entering or exiting except that it is used sometimes to put packages down there, then the entrance not used for entering or exiting isn't obligated in having a mezuzah. 
- The doorpost of a cellar that is lying flat on the ground is not obligated in having a mezuzah. 
- It is a dispute whether or not the doorway leading into an elevator requires a mezuzah. 
- A doorway is only obligated in a mezuzah if the room has 4 by 4 amot of space. If there's not 4 by 4 square amot but there is the same amount of area, such as 2 by 8 amot, there is a dispute whether the doorway is obligated in a mezuzah. In such a case one should put up a mezuzah without a bracha, or recite a bracha when putting up a mezuzah in a doorway that is obligated and then put up this mezuzah. 
- If a doorway only has one doorpost, such as if the lintel is connected to a wall, then if the standing doorpost is on the right, one should put up a mezuzah without a bracha or recite a bracha when putting up a mezuzah in a doorway that is obligated and then put up this mezuzah. If the standing doorpost is on the left, that doorway isn't obligated in a mezuzah.
- A roofed porch that has 4 amot by 4 amot of space leading up to a house is obligated in a mezuzah with a bracha. (If the area it surrounds is 16 square amah, one should put up a mezuzah without a bracha.)
Closets, Pantries, and Storage Rooms
- A doorway is usually obligated in a mezuzah if it has two doorposts that are 10 Tefachim tall and a lintel on top.  Here an exception:
- A small closet, such as a linen closet or electricity closet, that a person doesn't enter and only uses by takes things out of it isn't obligated in a mezuzah. However, if it is a large closet that is 4 by 4 amot and a person enters is obligated in a mezuzah without a bracha.
- A storage room requires a mezuzah.
- If there's a storage room such as an attic that you only use twice a year it is considered as though he doesn't use it at all and it doesn't require a mezuzah. However, if it is used more frequently such as once a month then it is obligated.
Bathrooms and Bedrooms
- A mezuzah should not be put up by the doorway to a bathroom, mikveh room, or a room people wash in and stand there undressed.
- A bedroom should have a mezuzah. However, when a couple is together if the mezuzah is on the inside of the door it should be covered with a single covering. If the mezuzah scroll is already covered with a single non-clear cover such as metal or non-clear plastic that is sufficient. However, if the scroll is in clear plastic and the case is clear it should be covered with something non-clear.Some poskim hold that the mezuzah should be covered with a double covering and so even if the case isn't clear the mezuzah needs another cover. According to these poskim, even if the scroll is rolled up and the case isn't clear that only counts as one cover since they are both meant and usually used for the mezuzah. Therefore, before the couple is together the mezuzah should be covered with an external covering such as a piece of clothing. Even if the case is clear it counts as a single cover. 
Shul and Bet Midrash
- A shul doesn't need a mezuzah unless people live in the shul building.
- A bet midrash doesn't need a mezuzah but because some rishonim hold that it should have a mezuzah it is proper to put up a mezuzah on a bet midrash without a bracha. The reason that the bet midrash is different than a shul is since talmidei chachamim use it day and night they consider it like their home.
Offices and Stores
- According to many poskim an office or store is obligated in a mezuzah even if it is only opened by day. However, since some poskim hold that it doesn't require a mezuzah if it isn't used by night in such a case a mezuzah should be put up without a bracha.
- A factory is the same as a store for the purposes of mezuzah.
- Some say that a school requires a mezuzah just as a store does.
- There is an obligation to put up a mezuzah on a summer home or any home that is lived in even for part of the year. 
Doorways to Courtyards and Cities
- The doorway to a courtyard or city is obligated in having a mezuzah on the right side as one enters.  In a city that has some non-Jews the city gate does not need a mezuzah.
- The electrical posts used for an eruv do not need a mezuzah even though they function as a doorway.
Doorway in a Room
- If there are polls or arch in the middle of a room that creates a doorway if the two halves of the room are used for the same purpose there is no obligation to put up a mezuzah on the polls, however, if the polls separate the room in two and they are used for different uses then the doorway created by the polls requires a mezuzah.
How the mezuzah should be placed
When It Is Put Up
- One may put up a mezuzah at night.
Which Is the Right Side?
- The criteria by which one can determine which side the mezuzah should be used are as follows:
- Entry: The mezuzah should be put up on the doorpost which is to one's right upon one's entering the house.  This criteria applies equally to the outer doors of the house to the rooms inside the house.
- Usage: If a room has two doorways if one of the two rooms that it connects is used more frequently then the mezuzah should be put up on the right side going into the room that is used more frequently.
- Majority of Walking: If the position isn't determined by entry or by which is used more frequently it can be determined by which room people walk from one room to another; if majority of the times people enter in one direction the mezuzah is placed on the right of that direction.
- Doorway: If the position of the mezuzah cannot be determined based on which direction is used for entry or which room is used more frequently it can be determined by the door. Since the door generally swings into the room (besides the outermost door of the house) the way the door swings can be considered the way one enters the room and the mezuzah is placed on the right side entering the room. However, if the mezuzah is determined based on the previous factors it doesn't matter which way the door swings.
- Doors to the Outside: Any door that goes from a place that is exempt from mezuzah to a place that is obligated in mezuzah should have the mezuzah on the right side entering into the place that is obligated in mezuzah. The mezuzah on the front door or back door of a house is always placed on the right side going into the house since the house is obligated in mezuzah and the street isn’t. A walk-in closet which is less than 4x4 amot the mezuzah is put on the right side going from the closet into the room since the closet isn’t obligated.
- Other factors include:
- Walking Route: Generally, the route by which a person walks around their house should be consecutively entering one room to another creating a circuit. For example, if the door of the house leads exclusively to room A which leads to room B and on to room C then the mezuzot should be placed on the right side of the door entering the house from the outside to A to B to C. However, this rule isn't ironclad, rather the first two rules are definitive.
- Doubt: If it is impossible to determine which side to put up the mezuzah based on the criteria of (1) whether the door is used more for entry or exiting, (2) which of the two rooms that the door connects is used more frequently, and (3) the door hinges because the door is used equally for entry and exiting, the two rooms are used equally and there is no door, according to some poskim there is no obligation to put up a mezuzah at all. Some poskim write that one should put up a mezuzah on both sides, but other poskim write that may not do so since it is [Bal Tosif], adding onto a mitzvah.
- The halacha that the mezuzah is placed on the right side of the door applies equally to a left handed person as well. 
- The side on which the mezuzah is placed depends on the norm of the people who use the house whether they own it, live there, are obligated in mezuzah or not. It doesn't depend on which way the homeowner wants to be the main direction of entry; it solely depends on which direction is used for more for entry in practice by the people who use it.
- If the mezuzah was placed on the left side of the door it needs to be taken down and put up on the right side with a bracha.
- If there's a back door that opens to an enclosed backyard that is completely closed then the mezuzah should be placed on the right side going into the backyard.
- If the back door opens into a backyard that has a gate to a courtyard or street then the back door should have a mezuzah on the right side going into the house because the house is used more than the backyard.
Straight or Diagonal
- While Sephardim place the mezuzah straight up, Ashkenazim place it on a slant, with the top leaning towards the inside and the bottom towards the outside. 
- The mezuzah should be placed at the beginning of the upper third of the height of the doorway but it should be placed at least a Tefach from the top of the doorway.  If it is not in the top third it isn't kosher. 
- If a doorway is very tall, according to Ashkenazim, one should put up the mezuzah at shoulder height.  However, according to Sephardim, one should place it in the upper third in all circumstances.
- If the doorway is arched there is a dispute whether the height of the doorposts includes the arched section where the doorway has a width of 4 tefachim. Therefore, if there is a small area which is arched and the doorway has a width of greater than 4 tefachim, it is possible to satisfy both opinions by placing it on the vertical section of the door but still within the top third of the doorway. (For example, if a doorway is 90 inches and the top 12 inches are arched and still has a width of tefachim, one should place the mezuzah in the vertical section above 60 inches.)
Having one's Mezuzot checked
- One should have one's Mezuzot checked by a sofer twice in seven years, or once in every three and a half years, and it is a pious practice to check them every year during Elul.
- If one's mezuzah became wet one should check it immediately.
- The mezuzah's of a publically owned building only need to be checked twice in fifty years.
The Bracha on putting up a Mezuzah
- In general, before putting up a Mezuzah in a doorway that is obligated in a mezuzah, one should recite the bracha. However, if one is putting up a mezuzah on a doorway that doesn't have a door or a doorway that leads into an area that doesn't have 4 by 4 amot square, no bracha is recited.
- Before putting up a mezuzah one should recite the bracha of "Asher Kideshanu Bemizvotav vetzivanu likboah Mezuzah" - " אשר קדשנו במצותיו וצונו לקבוע מזוזה" .  If one puts up several mezuzot at one time one bracha suffices for all of them.  In a situation like this one should be careful not to make a hefsek (pause) between mezuzot by talking.  If one did speak some poskim would require you to say a new beracha. 
- A shehecheyanu isn't recited when putting up a mezuzah on the doorpost. 
- If a mezuzah fell down and one is putting it up again one must recite a bracha before putting it up again if the doorway has a door and the room is at least 4 by 4 amot in size. 
- If one took down one's Mezuzot in order to have them checked by the sofer and they were found to be kosher, according to Ashkenazim one should put them back up without a Bracha of Lekvoh Mezuzah. According to Sephardim, one should make a bracha upon putting them back up after being checked by the sofer. If one checks the mezuzah by himself, he need not say a new beracha.  If a mezuzah was found to be not kosher, then a beracha is recited when it is replaced with a kosher one.  Please note that a bracha is only said when replacing the mezuzah if the doorway has a door and the room is at least 4 by 4 amot in size. (See above #The Bracha on putting up a Mezuzah).
- However, if one took down one's Mezuzah just to put it in a nicer case, one doesn't need to make a new Bracha when putting it up unless it was taken down for several hours so that one stopped thinking about the Mezuzah.
- When replacing the mezuzot, a new beracha is recited. 
- If someone is renting a house in Israel he is obligated to put up a mezuzah with a bracha immediately.  However, if one is renting outside Israel for less than 30 days isn't obligated to put up a mezuzah and if he wishes to be strict to put a mezuzah he should do so without a bracha. If he stays for more than 30 days and he put up a mezuzah previously he should make a bracha upon the mezuzot. Some say that one has to take down the mezuzah and put them up again and some say that one doesn't have to take it down to make a bracha upon it. It is proper to take it down check them and put them back up with a bracha.
- If someone is renting a house for more than 30 days, he is obligated to put up a mezuzah immediately. He does not recite a bracha if he puts it up within 30 days.
- Someone renting a bungalow for more than 30 days must put up mezuzah but some hold that no bracha is recited.
- A yeshiva dormitory requires mezuzot and they should be put up by the yeshiva and not the students.
Proper behavior when passing a mezuzah
- When one leaves one's house should kiss the mezuzah to remind one of the unity of Hashem, as discussed below. There are different opinions as to how exactly one should behave when passing a mezuzah. 
- When one enters or exits a room one should think about the unity of Hashem, our love for Hashem, and be awakened from the slumber of the vanities of the world. One should think that there's nothing that last forever except knowledge of Hashem, and immediately this will help a person follow the proper path. 
- One should be very careful with the mitzvah of mezuzah because it is a mitzvah that applies to everyone always. 
- Women are obligated in mezuzah. 
- There is a discussion among the poskim if women can ideally place the mezuzot. Many poskim write that it is even ideal for women to put up the mezuzot. 
- Ideally, a child should not place the mezuzah on a doorpost.  Sephardim hold that the child should put up the mezuzah for his doorway and when he becomes bar mitzvah'ed it should be taken down, checked, and put up again with a bracha.
- The doorway to a child's room should have a mezuzah for chinuch.
- In a room where the baby is changed if the mezuzah is on the inside of the door it should be covered.
- Even though it is technically permitted to have a child potty in a room with a mezuzah since the mezuzah is covered and above 10 tefachim it isn't proper to do so.
- Mezuzah on aish.com
- Rambam Sefer HaMitzvot Positive Commandment 15, Sefer HaChinuch Mitzvah 423, Kitzur Shulchan Aruch 11:1 from Devarim 6:9 and 11:20. Shulchan Aruch YD 285:1, Chayei Adam 5:13, Aruch Hashulchan 285:2 say that one should be very meticulous with this mitzva. Tur YD 285 writes based on the pasuk that follows in Parashat Ekev, 11:21, that one who is meticulous in this mitzva merits long life. Bach YD 285 and Aruch Hashulchan YD 285:3 write that a house with a mezuzah has extra protection.
- Maharil (responsa 94) bemoans the fact that many people think that it is sufficient to have one mezuzah per house when in fact every doorway requires its own mezuzah. The Darkei Moshe 286:4 cites the Maharil. Kitzur Shulchan Aruch 11:1 concurs.
- Chaye Adam 15:15 writes that a cellar door on the floor is exempt from mezuzah based on Kiddushin 22b that states that a doorpost lying on the ground isn't considered a doorpost. Kitzur Shulchan Aruch 11:20 and Aruch Hashulchan YD 286:41 concur.
- Rav Zilberstein (Tuvcha Yabiu - Hilchot Shecheinim 34) says that even if the elevator itself is not 4 by 4 amos- the doorpost from the hallway that leads into the elevator requires a mezuzah. However, Rav Moshe Stern (Be'er Moshe 2:88) says that no matter what an elevator will never require a mezuzah.
- Kitzur Shulchan Aruch 11:10 records a dispute between the Rambam and Rosh on this matter. Shulchan Aruch YD 296:13 writes the opinion of the Rambam that if the room has an area of 4 by 4 amot even if it isn't a square it is obligated in a mezuzah. The Shach 296:23 notes that the opinion of the Rosh is that the doorway isn't obligated unless there is a 4 by 4 amot square area. Due to this dispute, the Shach concludes that one should put up the mezuzah without a bracha or recite a bracha when putting up a mezuzah in a doorway that is obligated and then put up this mezuzah.
- Kitzur Shulchan Aruch 11:11, HaMezuzah VeHilchoteha 10:4
- HaMezuzah VeHilchoteha 3:10
- Shulchan Aruch YD 287:1, Kitzur Shulchan Aruch 11:11
- Pitchei Mezuzot 19:10-1 (p. 257), Minchat Yitzchak 3:103, 4:92:3
- The Gemara Yoma 11a cites a dispute between Rav Kahana and Rav Yehuda if a storage room needs a mezuzah if it isn't used for anything else. Rav Kahana held that this was a dispute in the tenayim. The Rif (Mezuzah 6b) and Rosh (Mezuzah no. 15) hold that it is obligated, while the Rambam Mezuzah 6:7 holds it is not. Shulchan Aruch YD 286:2 accepts the opinion of the Rif. Yalkut Yosef YD 285:30 writes that one should put up a mezuzah without a bracha.
- Rav Hershel Schachter in “The Laws of Mezuzah” (min 0-2)
- Yoma 11b, Shulchan Aruch YD 286:4, Aruch HaShulchan YD 286:5, Yalkut Yosef 285:43
- Shulchan Aruch YD 285:5, Aruch Hashulchan 286:13
- Aruch Hashulchan 286:12-15 proves that the Bet Yosef's opinion that the bedroom needs a mezuzah and it is sufficient to have it covered with one covering. Yalkut Yosef YD 285:41 and Halichot Olam v. 8 p. 302 agree. Ben Ish Chai (Shana Sheniya, Ki Tavo, no. 16) writes that such is the minhag.
- Divrei Chamudot (Mezuzah no. 46), Magen Avraham 40:2, Ben Ish Chai (Shana Sheniya, Ki Tavo, no. 16) citing the Yad Ketana 13
- The Gemara Yoma 11a establishes that a shul that no one lives in doesn't need a mezuzah. The Gemara 11b implies that the reason for this is that only a house that belongs to clearly designated owners needs a mezuzah excluding a shul that belongs to the community or public. Tosfot 11b s.v. shein accepts this understanding and says that a privately owned shul would require a mezuzah. He uses this idea to explain the Yerushalmi Megillah which speaks about a mezuzah on a shul unlike the Gemara Yoma and Brachot 47a that assumed that a shul doesn't need a mezuzah. The Rif (Hilchot Mezuzah 6b), Rosh (Mezuzah 6b), and Rambam (Mezuzah 6:6) distinguish between a shul in a city is exempt but in a village it is obligated because most likely people live in the shul building. The Shulchan Aruch YD 286:3 concludes that a shul does not require a mezuzah.
- The Rambam Mezuzah 6:6 writes that a shul doesn't need a mezuzah since it is an area of kedusha. There is a difficulty regarding the Rambam's opinion regarding its source from the Gemara Yoma 11b which seems only to apply this reason to the bet hamikdash. The Chatom Sofer YD 291 however explains that the Rambam means that even though the shechina dwells in the shul it isn't considered as though it is a house used for dwelling since it needs to be used for human dwelling to be obligated in mezuzah.
- The Gemara Yoma 11b treats a shul and bet midrash equally regarding mezuzah. Tosfot Yoma 11b writes that based on Yoma it sounds like there is no obligation to have a mezuzah for a bet midash, but Menachot 33a implies otherwise. Tosfot concludes that if it is privately owned or if it has a door from the bet midrash that opens into someone's private house then that door is obligated in a mezuzah. The Rosh (Mezuzah no. 10) writes that the Maharam Rotenberg learned from the Yerushalmi that a bet midrash should have a mezuzah. He added that a evil spirit bothered him when he slept in the bet midrash during the day until put up a mezuzah. Shulchan Aruch YD 286:10 concludes that a bet midrash does not need a mezuzah but since some say it should have one it is proper to put up one without a bracha. The Shach 286:19 explains that the reason to distinguish between a shul and bet midrash is that the talmidei chachamim live in the bet midrash day and night.
- The Gemara Yoma 10a establishes that according to the rabbis a sukkah does not require a mezuzah since it is a temporary dwelling. The Tur YD 286:11 extends this to a boat and store that are also considered a temporary dwelling which doesn't require a mezuzah. The Shulchan Aruch 286:11 concurs. The Taz 286:10 explains that even if the store is used every day it is exempt since no one lives in it at night. He adds obviously that if someone has a store in their house they require a mezuzah. However, the Perisha 286:22 wonders if store nowadays are exempt since they are permanent. In fact, the Pitchei Teshuva 286:14 cites the Yad Ketana who argues that a store that is set up for a temporary marketplace for a week or so is exempt from a mezuzah, but an established store requires a mezuzah. Yalkut Yosef YD 285:36 agrees. See further Yabia Omer 10 p. 350 and Halichot Olam v. 8 p. 302. Yalkut Yosef writes that a mezuzah should be put up without a bracha because of the dispute but if someone recites a bracha they have what to rely upon. The Ohel Aryeh 4:8 writes that perhaps the Taz would agree nowadays since the stores are open partially into the night and since it is used by day and night it is considered permanent.
- Yalkut Yosef YD 285:37
- Yalkut Yosef YD 285:38
- Yoma 11a, Shitah Mikubeset b”m 102, Rav Hershel Schachter in “The Laws of Mezuzah” (min 0-2)
- Yoma 12a, Shulchan Aruch YD 286:1, Kitzur Shulchan Aruch 11:2-3
- Yoma 11a. Rama YD 286:1 quoting the Aguda that even if some non-Jews live in the city they are exempt from mezuzah on the city gate. The Taz 286:3 explains that the exemption is based on a danger.
- Chazon Ish YD 172:3 writes that even though the electrical posts with the wires on top can serve as doorways to enclose an eruv for Shabbat (under certain conditions) they do not need a mezuzah since the mezuzah won't be guarded and also some non-Jews might live in the city. Rav Hershel Schachter in “The Laws of Mezuzah” (min 48-53) explained that the factors why we don’t put up a mezuzah for a communal eruv are both because it might get ruined by weather or stolen. Additionally, it is because the Derech Hachaim Siddur writes that since the poles don’t devide the way the area is used (tashmisho echad) and it is more open than it is closed (omed murebeh al haparutz) for mezuzah purposes the poles don’t create a doorway. Therefore, an eruv doesn't require a mezuzah even in a Jewish community.
- Rav Hershel Schachter in “The Laws of Mezuzah” (min 48-53) quoting the Derech Hachaim Siddur
- Gemara Menachot 32b, Tur 289, Shulchan Aruch 289:2, Levush 289:2, Chayei Adam 15:17, Aruch Hashulchan 289:9. Taz 289:3 writes that the mezuzah is still kosher if the mezuzah isn't on the outer tefach.
- Rav Mordechai Eliyahu (comment on Kitzur Shulchan Aruch 11:10), Ben Ish Chai Parashat Ki Tavo Year 2: Halacha 4, Shevet Hakehati 1:277, Mezuzat Baitecha 289:6, Rivevot Ephraim 7:369.
- Gemara Menachot 33b, Rambam Hilchot Mezuzah 6:12, Shulchan Aruch 289:2, Taz 289:3, Levush 289:2, Aruch Hashulchan 289:5, Kitzur Shulchan Aruch 11:3, Kitzur Shulchan Aruch of Rav Mordechai Eliyahu 11:3.
- Igrot Moshe YD 4:43:4
- The Levush 289:3 writes that the side rooms of a house which open to the main room which was warm in the winter should have a mezuzah going into the main room since it is used more than the side room. This rule trumps the direction of the door. This is accepted by the Shach 289:6 who comments that it is obvious. The Kitzur Shulchan Aruch 11:4, Chayei Adam 15:18, Chelkat Yakov YD 161, Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42), Igrot Moshe 4:43:4 and Hamezuzah Vehilchoteha 11:11 agree.
- The Chelkat Yakov YD 161 proves that the Mordechai is the source for the Levush. The Mordechai cited by Bet Yosef YD 289 writes that the gemara needed a doorway to resolve the question of a man's room and a woman's room next to one another because they are both equally used and open to the public. However, between a vestibule or foyer and the main room of the house that is used commonly certainly the mezuzah is placed going from the vestibule and the main room since it is used more. He adds that this is also true even if the main room is also open to the public and the vestibule is open to a courtyard.
- The Chelkat Yakov explains the Mordechai to mean to add that even though when the vestibule is open to a courtyard and the main room to the public people will use the vestibule more often as an exit than an entrance, nonetheless, since the main room is used more than the vestibule, we view the entrance between the vestibule and the main room as an entrance and not an exit. In this he is proving that the rule of majority of walking is trumped by majority of usage.
- Igrot Moshe 4:43:4 writes that rule of majority of walking trumps the rule of usage and also the rule of doorway. His logic is that the room that is used more is only an indication of which way people walk a majority of the time but the main factor is the way people walk. He holds that the way people enter a majority of the time is an application of the deoritta halacha to put a mezuzah on the right as a person enters.
- Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42) holds that the factor of looking at the majority of the way people walk one room to another trumps the rule of the way the door is placed. Aruch Hashulchan 289:8 and Igrot Moshe YD 1:176 agree. However, Igrot Moshe 4:43:1 further. Hamezuzah Vehilchoteha 11:12 holds that this factor is to be used after the door rule. Chelkat Yakov YD 161 agrees.
- Menachot 33a, Shulchan Aruch YD 289:3, Aruch Hashulchan 289:6
- Mordechai cited by Bet Yosef YD 289, Shach 289:6, Aruch Hashulchan 289:7, Igrot Moshe YD 4:43:3, Hamezuzah Vehilchoteha 11:11
- Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42) explained that this is the first factor by which a person determines on which side of the door the mezuzah is placed.
- Igrot Moshe YD 4:43:4
- The Yavetz 70 held that in a case of doubt that can't be resolved should have a mezuzah on both sides. The Maharam Shik YD 287 argues that this would violate the prohibition of adding a mitzvah, Bal Tosif.
- Strict: HaMezuzah Vehilchoteha 11:13 citing Mezuzat Beytecha 289:16 quoting the Chazon Ish and Minchat Yitzchak 1:9 agree with the Maharam Shik. Chelkat Yakov 162 holds that it is a rabbinic form of Bal Tosif.
- Lenient: Yabia Omer 6:2:6 cites the Binyan Tzion 100 and Rav Shlomo Kluger in Kinat Sofrim 40 who say that it isn't since one is pasul and one is kosher (Shulchan Aruch OC 34:2 and Magen Avraham 34:3). Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42) explained it was not Bal Tosif since one was only trying to be fulfill the mitzvah according to all opinions similar to wearing Rashi and Rabbenu Tam's tefillin simultaneously. See Rav Mordechai Eliyahu's comment to Kitzur Shulchan Aruch 11:4 where he rights that if there is a doubt as to which side the mezuzah should be placed there is a safek as to what one should do.
- Exempt: Igrot Moshe YD 1:176 holds that if the direction in which the mezuzah should be put because it isn't used more for entry than exiting, the rooms it connects are used equally, and there is no door, then there is obligation to put up a mezuzah at all. He quotes the Yavetz who says to put up a mezuzah on both posts out of doubt but he disagrees. He also rejects the opinion of the questioner to put up a mezuzah on the side of his choice.
- Mordechai Halachot Ketanot 962, Bach 289:5, Shach 289:5, Levush 289:2, Chayei Adam 15:17, Kitzur Shulchan Aruch 11:3, Aruch Hashulchan 289:5, Kuntres Hamezuzah (page 102, note 22).
- Igrot Moshe YD 4:43:2 unlike the opinion of the Daat Kedoshim 289:11
- Hamezuzah Vehilchoteha 11:10, Kitzur Shulchan Aruch 11:3
- Chelkat Yakov YD 161 based on the Maharil. Even though the Bet Meir and Chavot Daat ask on the Maharil since most poskim accept the Maharil we follow his opinion. His opinion is based on the concept that you walk from the house to the backyard and since the back door is an entrance to the backyard which has no other entrance then the mezuzah must be on the right entering the backyard. Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42) agreed.
- Chelkat Yakov YD 161 writes that even though the Maharil would insist that from the house to the courtyard you need to put up a mezuzah going into the courtyard, the Bet Meir, Chavot Daat, and many others would hold that since the house is used more than the courtyard then we view the back yard as an entrance to the house rather than an entrance of the courtyard. Since the house is used more than the courtyard that trumps the rule of the fact that the majority of the walking is from the house to the courtyard. Rav Hershel Schachter in “The Laws of Mezuzah” (min 34-42) agreed.
- Rashi Menachot 33a s.v. pesula, Shulchan Aruch 289:6, Ben Ish Chai Ki Tavo Year 2 Halacha 7. This was also the minhag of the Gr"a (Biurei Hagra 289:14. Also see Orchos Rabbeinu 1:page 378:27)
- Rabbenu Tam cited by Tosfot Menachot 33a s.v. ha, Rama 289:6, Levush 289:6, Chayei Adam 15:19, Minchas Elazar 1:36:1, Pitchei Mezuzahs 289:57, Chovat Hadar 9:footnote 20. Chovat Hadar 9:footnote 20 explains that the reason for this is that the opinion of Rashi says if you place it sideways it is not kosher, while Rabbenu Tam Menachot 33a s.v. ha holds that if it is straight up it is not kosher, so Ashkenazim try to fulfill the mitzvah according to both opinions.
- Kitzur Shulchan Aruch 11:5, Rashi Menachot 33a s.v. “bitechila,” Rambam Hilchot Mezuzah 6:12, Tur 289, Prisha 289:6, Shulchan Aruch 289:2, Levush 289:2, Chayei Adam 15:17, Pitchei Mezuzahs 289:24, Chovat Hadar 8:2:4, Teshuvot Vihanhagot 2:539. See Yabia Omer YD 2:21 where Chacham Ovadia Yosef quotes poskim who say that if it was placed higher than the beginning of the top third it should be moved without a beracha to there, but himself disagrees.
- Tur 289, Shulchan Aruch 289:2, Levush 289:2, Kitzur Shulchan Aruch 11:5
- Beit Yosef 289, Shach 289:4, Taz 289:3.
- Yerushalmi Megillah 4:12, Tosfot Yoma 11b s.v. shein, Shach 289:4
- Yalkut Yosef YD 285:77
- Chovat Hadar (p. 59, n. 35)
- According to the opinion that the arched section is included the mezuzah should be placed at 60 inches (2/3 of 90) and above and according to the opinion that the arched section isn't included the mezuzah should be placed at 52 inches (2/3 of 78) and above. To satisfy both opinions one can place it at 60 inches where the doorpost is still vertical.
- Yoma 11a, Shulchan Aruch YD 291:1, Kitzur Shulchan Aruch 11:25, Yalkut Yosef YD 285:92
- Rav Mordechai Eliyahu (comment on Kitzur Shulchan Aruch 11:22)
- Yoma 11a, Shulchan Aruch YD 291:1
- Shulchan Aruch YD 296:15 writes that a doorway that doesn't have a door is obligated in a mezuzah, however, some disagree. The Shach YD 296:25 writes that because of this dispute one should put up the mezuzah without a bracha, or recite a bracha when putting up a mezuzah in another doorway that is obligated, and afterwards put up this mezuzah as well. Similarly, Shulchan Aruch YD 296:13 writes the opinion of the Rambam that if the room has an area of 4 by 4 amot even if it isn't a square it is obligated in a mezuzah. The Shach 296:23 notes that the opinion of the Rosh is that the doorway isn't obligated unless there is a 4 by 4 amot square area. Due to this dispute, the Shach concludes that one should put up the mezuzah without a bracha or recite a bracha when putting up a mezuzah in a doorway that is obligated and then put up this mezuzah.
- Gemara Menachot 42b, Rambam Hilchot Mezuzah 5:7, Kitzur Shulchan Aruch 11:7, Aruch Hashulchan 289:3
- Kitzur Shulchan Aruch 11:7, Aruch Hashulchan YD 289:4, Shevet Ha’Levi 6:160, Rivevot Ephraim 3:508, Az Nidberu 3:61
- Mezuzat Baitecha 289:6, Rivevot Ephraim 2:29:21, Pitchei Mezuzat 289:10, Kuntres Hamezuzah 289:8
- Chovat Hadar 11:9, Kuntres Hamezuzah 289:8. Mikdash Miat 289:6 and Birchot Habayis 59:1 disagree.
- Chovat Hadar 11:2, Mezuzat Baitecha 289:3
- Kitzur Shulchan Aruch 11:7, Beer Moshe 6:6, Chovat Hadar (11:15:footnote 29), Kuntres Hamezuzah 289:7, Avnei Yashfei 1:207:3-4, Rivevos Ephraim 2:28:5. Orchos Rabbeinu (v. 3, p. 178 #38) however, disagrees.
- Kitzur Shulchan Aruch 11:7 writes that there's a doubt if one should make a bracha if a mezuzah was taken down to check it.
- Yalkut Yosef YD 285:93 writes that one should recite a bracha if they were taken down to be checked by a sofer.
- Ben Ish Chai Parashat Ki Tavo Year 2 Halacha 8, Pitchei Teshuva 289:1, Aruch Hashulchan 289:4, Chovat Hadar 11:14
- Kitzur Shulchan Aruch 11:3,5, Rivevot Ephraim 1:19, Beer Moshe 2:92:13, Kuntres Hamezuzah 289:6, Chovat Hador 11:11:footnote 20, Yabia Omer YD 3:17
- Yalkut Yosef YD 285:94
- Maharam Shik YD 285, Rivevot Ephraim 7:239, Beer Moshe 2:92, Avnei Yashfei 1:207:1, Doleh Umashke (p. 275, footnote 69) quoting Rav Elyashiv and Rav Nissim Karelitz.
- Yalkut Yosef YD 285:114
- Yalkut Yosef YD 285:115
- Yalkut Yosef YD 285:114
- Ohel Aryeh 5:3 writes that a bungalow rented for more than 30 days requires a mezuzah, some say with a bracha and some argue. He cites the Tarshish Shoham 52 who holds that the mezuzah should be put up on the 31st day without a bracha since the bungalow colony is a temporary dwelling just to escape the city for the summer.
- Ohel Aryeh 4:15 explains that since the yeshiva bachur can be kicked out of his room and it isn't really a rental but a payment for a place to stay the yeshiva needs to put up the mezuzot in the dormitory.
- Kitzur Shulchan Aruch 11:24 writes that one should kiss the mezuzah in order to remind oneself of Hashem's unity. Kav HaYashar (ch. 1) writes that touching the mezuzah and offering a short prayer when one leaves one's house affords oneself protection from spiritual dangers. Orchos Rabbeinu (v. 3, p. 164) writes that the Chazon Ish looked at the mezuzah without kissing it when he passed by one.
- Kitzur Shulchan Aruch 11:23
- Kitzur Shulchan Aruch 11:23
- The Gemara Kiddushin 34a explains that since women can also use the reward of long life, written next to the parsha of mezuzah, the mitzvah of mezuzah also applies to them. The same appears in Yoma 11b. This is codified by the Rambam Hilchot Mezuzah 5:10, Shulchan Aruch YD 291:3, and Shach 291:4.
- Shevet Halevi 2:158:3, Kinyan Torah 2:58 and Chovat Hadar 9:3 write that women can put them up even ideally. Rav Hershel Schachter (Be'ikvei HaTzon p. 9) writes that the halacha follows the opinion that says women may put up mezuzot. Beer Moshe 2:100 and 6:79:5 as well as Teshuvot Vihanhagot 4:238:6 write that it is ideal for a man to put up the mezuzot, however, if a women did put them up, it need not be removed.
- Tzitz Eliezer 14:75, Chanoch Lanaar 35:4
- Yalkut Yosef YD 285:15
- Shulchan Aruch YD 291:3
- Yalkut Yosef (Sovah Semachot v. 1 ch. Mekomot Hachayvim Bmezuzah no. 39)
- Yalkut Yosef YD 285:7