Rambam - 3 Chapters a Day

The Rambam’s words appear to indicate that when the window was first built, the neighbor did not have a courtyard below it. Sefer Me’irat Einayim 154:50 (see also the Tur), however, explains that the Rambam would agree that this law applies even when the courtyard existed before the window was opened, and when the window was opened, the owner of the courtyard did not object. The Turei Zahav, however, takes issue with the explanation offered by the Sefer Me’irat Einayim and states that the Rambam’s ruling applies when the person built the window over a ruin or empty property and the courtyard was built later.
Support for the Turei Zahav’s interpretation can be brought from Halachah 6, which would be redundant according to the interpretation of Sefer Me’irat Einayim.

As stated in Chapter 2, Halachah 12, every person has the right to privacy in his courtyard. Nevertheless, for the reason the Rambam proceeds to explain, an exception is made in this particular instance.

According to the interpretation that the Rambam is speaking about a situation where the window existed before the courtyard, the leniency is granted because the owner of the window built his window when it was permitted. Thus, even after the building of the courtyard, he is not required to close it.

I.e., the owner of the courtyard.

He has a right to build the wall, for he is building it within his own property.

If, despite leaving this much of a separation, the wall till casts a shadow, the shadow is not considered significant. For as long as there are four cubits between the wall and the window, there is enough space for light to penetrate [Shulchan Aruch (Choshen Mishpat 154:21)].

So it will not cast a shadow as above.

The Maggid Mishneh mentions that if the owner of the courtyard builds the wall further away, he must build it higher, because otherwise he will be able to see from beyond the wall.

Sefer Me’irat Einayim 154:52 emphasizes that permission is granted only in a situation where it is certain that the building of the: second wall will not cause any structural weakness to the first wall.

For the wall does not enable the owner of the courtyard to see through the window.

I.e., perpendicular to the wall in which the window is located.

The Ramah (Choshen Mishpat 154:22) emphasizes that the handbreadth is measured from the window itself, and not from its frame.

This follows the Rambam’s interpretation of Bava Batra 22b. Rashi offers a different interpretation, which requires the owner of the courtyard to do both: build the wall higher and make it narrow on top. Although Rabbenu Asher and the Tur follow Rashi’s view, both the Shulchan Aruch (Choshen Mishpat 154:22) and the Ramah follow the Rambam’s understanding.

The wall must be narrow and pointed on top, so that a person will not be able to stand or sit on it.

Otherwise, sufficient light will not reach the window.

I.e., there must be an equal space between the window and both walls. One may not leave three cubits on one side of the window and one cubit on the other.
From the Rambam’s wording, it appears that he maintains that the width of the window is included in these four cubits. The Tur, by contrast, requires that there be four cubits of empty space between the walls in addition to the width of the window. The Shulchan Aruch (Choshen Mishpat 154:23) quotes the Rambam’s words.
If the window is itself four cubits wide, a handbreadth must be left on either side between it and the wall (Maggid Mishneh).

A substance that produces shade. The intent could be for use as a sukkah during the holiday of Sukkot or for shade against the summer sun. Needless to say, this applies with regard to an ordinary roof.

And prevent the window from serving as a source of light.

Note the Lechem Mishneh, which explains that the word “accordingly” does not refer to the concepts that immediately precede it. Some manuscript versions of the Mishneh Torah consider this the beginning of a new halachah.

And it is not easy for the owner of the window to look through it.

As stated in the previous halachah, if the owner of the courtyard desires, he can prevent the construction of the window. If, however, he does not protest the window’s construction, according to the Rambam, the owner of the window acquires the right to maintain the window. He does not have to wait three years (as Rabbenu Asher maintains) or purchase that right from the owner of the courtyard.

With regard to the division of a courtyard, as the Rambam states in Chapter 11, Halachah 4, a colleague can argue that although he previously was not bothered by the invasion of his privacy, he is bothered at present and would like a wall constructed. It seems, however, that although significant, the invasion of privacy from a window is not very severe. Hence, once a person grants permission for the window, it cannot be retracted.
There are other authorities – among them, Rabbenu Yitzchak Alfasi and the Ramban – who maintain that the laws regarding privacy for a window are the same as those that govern a courtyard, and the owner of the courtyard may always protest against the window. The Shulchan Aruch (Choshen Mishpat 154:7) and the Ramah, however, rule according to the Rambam’s view.
The Ramah does emphasize that although the owner of the window is allowed to maintain the window, he is not allowed to watch the owner of the courtyard through it. On the contrary, doing so violates a prohibition.
Even with regard to a small window, near which the owner of the courtyard may build a wall, as stated in the following halachah, once permission is granted for such a window to be opened, it cannot be required to be closed.

The Ra’avad differs with the Rambam and reverses the rulings, explaining that a small window may always be blocked by a wall and with regard to a large window, it depends whether it is high or low on the wall. The Shulchan Aruch (Choshen Mishpat 154:10) quotes the Rambam’s ruling.

He may not, however, demand that the window be closed.

E. g., for the view it provides or in order to speak to a colleague (Kessef Mishneh).

I.e., these were the primary reason for its being opened, even though it also serves as a source of light. According to the Rambam, everything depends on the intent of the person who opened the window (Kessef Mishneh). The Tur and the Ramah (Choshen Mishpat 154:10) differ and maintain that the decision lies in the hands of the judge and the structure of the window.

I.e., just as a person can establish the right to open a window, so too, the owner of an adjacent property can establish the right to block or close a window.

The Ra’avad mentions a different perspective, positing that there is a difference between a window that is closed – in which instance he agrees with the Rambam that the owner of the window must protest immediately or lose his right – and a window that is blocked by a structure – in which instance, he grants the owner of the window 30 days to protest. Although in certain instances (see Chapter 8, Halachah 7), the Rambam will also allow 30 days to protest, in this instance he maintains that the protest must be lodged immediately.

The Tur and the Ramah (Choshen Mishpat 154:12) offer a slightly different perspective, maintaining that the owner of the adjacent property must produce proof that he has a right to close or block the window or at least issue a claim that the owner of the window never had legitimately established his right to open it.

Note the parallel in Chapter 4, Halachah 6.

Who were renowned for their lack of hospitality and unwillingness to help others.

Implied is that if any – even a slight – loss is caused, we do not compel him to accept the proposition (Tz’ror HaKessef).

For other examples of this principle, see Chapter 12, Halachah 1 and Hilchot Sechirut 7:8.

For the owner of the courtyard may feel that the new window will compromise his privacy more than the previous one did.

This addition is necessary, for if he desired merely to close a portion of the original window, there would be no reason to prevent him (Beit Yosef, Choshen Mishpat 154).

Or two partners (Hagahot Maimoniot).

The Maggid Mishneh explains that this law applies when they carefully evaluated every element of the inheritance with the exception of the open space. If, however, they made a general statement - that this property is equal to this property - the open space is considered to be part of the value of the property.

A porch with three walls and a roof, with the fourth side left open.

Since at that time, the brother did not state that the open space was important to him, he cannot lay claim to it later, saying that he would like the house to remain in the same condition as it was when owned by his father.
Nevertheless, neither of the brothers can build in front of the windows of a home, for depriving a home of light is considered to be making it an undesirable dwelling [Ramah, (Choshen Mishpat 154:27)].

If, however, the projection extends over a courtyard that is jointly owned by several people, this restriction does not apply [Tur, Shulchan Aruch (Choshen Mishpat 153:5)].

If there were no danger of the projection-owners invading the privacy of the owner of the courtyard, he would be allowed to make use of the empty space, for when one person will derive an advantage and the other will not suffer any loss, the person is granted the right to that advantage. (See Chapter 7, Halachah 8 and notes.) Nevertheless, this is not allowed in the present instance, for there is a real danger of loss of privacy.

And the owner of the courtyard cannot, at a later time, demand that the projection be removed.
As explained in Chapter 11, Halachah 4, and as mentioned in the notes on Chapter 7, Halachah 6, the projection-owner’s right is established immediately. He does not have to wait three years, nor must he produce a claim that legitimizes his construction of the projection. All that is necessary is for him to produce proof that the owner of the courtyard saw the projection and did not protest immediately. (See the Rambam’s Commentary on the Mishnah, Bava Batra 3:6.)
The Tur and the Ramah (Choshen Mishpat 153:2) differ and maintain that three years must pass before the owner of the projection establishes his right to it. They also maintain that if the projection is not more than a square handbreadth, the owner of the projection can never establish his right to use it. Indeed, the owner of the courtyard may himself use the projection and prevent the person who built it from using it.

For a square handbreadth is considered a space of significant size.

Although he has a right to use the projection whenever he desires, as stated in Halachah 1, he may not prevent the owner of the courtyard from building below it.

Sefer Me’irat Einayim 153:6 maintains that the owner of the courtyard may even have the projection removed entirely. Since it was never large enough to be significant, although the owner of the projection was given permission to use it while it existed, the courtyard owner may remove it whenever it becomes an obstruction to his own use of the courtyard space.

The Tur and the Ramah (Choshen Mishpat 153:4) state that the same laws apply when the projection is one handbreadth long and four handbreadths wide.

The Rashbam (Bava Batra 59b), the Maggid Mishneh, and the Sefer Me’irat Einayim 153:8 explain that a space one handbreadth by four handbreadths is very significant. Since the owner of the courtyard has consented to granting the owner of the projection a space this size, we assume that he was willing to grant him a space four handbreadths by four handbreadths.
The Ra’avad differs with the Rambam on this point and maintains that the owner of the projection must produce proof that the owner of the courtyard sold the right to extend a projection. This reflects the difference of opinion mentioned in the notes on Halachah 1.

Even if the projection is longer than four handbreadths, the owner of the projection is not entitled to make it more than four handbreadths wide (Rashbam loc. cit.).

The Maggid Mishneh states that the measure of 10 handbreadths was not mentioned in the Talmud. Nevertheless, it was accepted by our Rabbis, because that is a minimum size of a house.

This is the definition of the term, an Egyptian ladder, mentioned in the Mishnah, Bava Batra 3:6.

The Siftei Cohen 153:10 writes that a field is mentioned to teach us the definition of the term courtyard used in this instance: that we are not speaking of a courtyard used for personal use, for in such a place using the ladder would certainly be an invasion of privacy and the owner of the courtyard could prevent him from doing so, as he can prevent him from constructing a projection. Instead, the intent is a courtyard that is used like a field.

I.e., he places the ladder in his neighbor’s property and leans it up against the wall, so that he could climb up the ladder and gain access to his own property.

Since the ladder is small, we do not consider it as a matter of consequence, since the owner of the courtyard would not be bothered by its use. Therefore, the fact that he does not protest is not considered proof of his acceptance of the presence of the ladder.
The Ramah (Choshen Mishpat 153:13) states that if the owner of the ladder affixes the ladder with nails and the owner of the courtyard does not protest, he has established his right to the ladder, even if the ladder is small.

He may not, however, prevent the neighbor from placing the ladder there, as stated in the conclusion of the halachah.

This is the definition of the term, a ladder from Tyre, used in the Mishnah.

The Rambam follows his opinion – reflected in the previous halachot – that by not protesting the ladder’s presence when he first saw it, the owner of the courtyard acquiesced to its remaining there.
In this instance, as in the previous halachot, the Tur and the Ramah (Choshen Mishpat 153:16) maintain that it takes three years before the owner of the ladder establishes his right to maintain it. (See also Sefer Me’irat Einayim 153:32.)

For as mentioned above, it does not constitute an invasion of privacy.

As explained in Chapter 7, Halachah 8 and notes, not allowing such consideration is termed “the attribute of Sodom,” which our Sages would compel the Jews not to emulate.

Sefer Me’irat Einayim 153:15 states that this applies both to draining off rain water and to removing sewage water.

A larger pipe than the pipe mentioned in the first clause. In his Commentary on the Mishnah (Bava Batra 3:6), the Rambam states that this applies to a wooden gutter that extends over the entire length of a wall and then has the water flow down through a drainpipe. This is done in order to protect the wall from erosion by the water.

Because this concentrated flow of water could present a source of discomfort – and perhaps damage – to the owner of the courtyard.

As in the previous halachot, according to the Rambam, if the owner of the courtyard does not protest, the owner of the roof establishes his right to the drainpipe immediately. The Tur and the Ramah (Choshen Mishpat 153:6) maintain that it takes three years before the owner of the roof establishes his right to the drainpipe. See Sefer Me’irat Einayim 153:32.

If, however, the owner of the roof removes the drainpipe, and the owner of the courtyard does not protest, he is considered to have waived his right to the water [Ramah (loc. cit.)].

For he could make positive use of the water that flows into his courtyard.

On the same side (Meiri).

Moreover, the owner of the courtyard may not move the pipe anywhere if doing so inconveniences the owner of the roof [Ramah (Choshen Mishpat 153:8)].

The Maggid Mishneh explains that all the structural changes mentioned in this halachah do not increase the quantity of water flowing into the neighbor’s courtyard; they merely alter the rate at which the water flows in. If, however, he makes changes that increase the quantity of water that flows into the courtyard, his neighbor may protest. See Shulchan Aruch (Choshen Mishpat 153:11).

Even if one of the neighbors refrains from inserting beams for a long period of time, he does not forfeit his right to do so [Ramah (Choshen Mishpat153:14)].

With this phrase, the Rambam clarifies two points:
a) that the beams may be inserted more than half-way across the wall, indicating that the two are considered partners in the entire wall. It is not that half belongs to one and the other half to the other.
b) that their weight is not a factor. The Ramah (Choshen Mishpat 153:14) infers that in this regard there is a restriction. The beams may not be heavier than what is ordinary for that region.

For using the wall for any purpose may detract from its strength.

Here the term is not being used in the ritual sense, but rather as a reference to a structure similar to that used on the holiday, but employed for shade in the summer.

I.e., although he had a right to protest, he did not exercise it as long as he thought that the structure was only temporary and thus would not cause lasting damage to his wall.

For the owner of the wall was obviously doing him a favor and allowing him to make use of the wall for the holiday. The owner of the wall may require him to remove the beam during the holiday as well.

Actually eight days, for he is forbidden to remove the sukkah on Shemini Atzeret, the holiday that follows the seven days of Sukkot. In the diaspora, this also applies on Simchat Torah, the holiday that extends Shemini Atzeret in the diaspora. Moreover, if Simchat Torah is followed by the Sabbath, an additional day is granted.

For once the sukkah is left beyond the time when it is necessary for ritual purpose, the owner of the beam is making it obvious that his use of the wall is not merely a temporary matter.

For this is clearly a sign that he intended to leave the beam there permanently.

This shows that he consents to his use of the beam.

In this halachah, the Rambam follows the approach reflected in the previous halachot, that even though the person who inserted the beam is overstepping his rights, if the other neighbor does not object, the person establishes his right to the use of the property immediately. In this instance as well, the Tur and the Ramah (Choshen Mishpat 153:16) differ and maintain that it takes three years before the owner of the beam establishes his right to maintain it. (See also Sefer Me’irat Einayim 153:32.)
The Tur also maintains that if the owner of the beam admits that the wall belongs to the other colleague, he must also claim to have purchased the right to place his beam in the wall from his colleague.

This law is not explicitly stated in the Talmud. Nevertheless, from the fact that there is a difference of opinion (Bava Batra 6a) with regard to whether one may replace a lighter beam with a heavier one, we may conclude that although the Rambam follows the more lenient opinion in that instance (see the previous halachah), the leniency has its limits (Maggid Mishneh).

Although the other person protests and claims that he is the owner of the entire wall, unless there are witnesses, we accept the claim of the owner of the beams for the reason the Rambam continues to explain.

This is accepted as proof of his partnership in the wall. For had the other owner been the sole owner of the wall, it is unlikely that he would have let him insert his beam into the wall.

His word is accepted regardless of the amount of time his beams had been inserted into the wall. There is no need for them to remain there three years (Maggid Mishneh).
The Maggid Mishneh explains that this ruling is also not explicitly stated in the Talmud and is the product of the Rambam’s deductive reasoning. The Maggid Mishneh, however, questions the conclusion, noting that there are authorities (Rabbenu Tam, Rabbenu Asher, as reflected in the rulings of the Tur and Sefer Me’irat Einayim 153:36) who require that the person who inserted the one beam have had that beam inserted for at least three years.
The Maggid Mishneh explains that the Rambam’s ruling (and that of Rabbenu Asher, who accepts such a claim if made after three years) applies only when the person claims that he was a partner in the construction of the wall from the very beginning, but until this time, he had not desired to use it for his beams. If, however, he admits that it was his colleague who constructed the wall originally, the fact that he inserted a beam [or beams] there is of no consequence unless he built a roof. Nevertheless, as the Kessef Mishneh and the Ramah (Choshen Mishpat 153:18) indicate, this interpretation is not accepted by all authorities. The Tur maintains that if a person’s beams are inserted into a wall, we accept his claim to partnership in the ownership of the wall even if he admits that he did not originally build the wall, but merely purchased (or was given) a share in it afterwards. In such an instance, should the wall fall, he receives half of the stones of the wall, but not half of the land on which it was built.

Since he does not have witnesses to support his claim, the oath is required to prove the integrity of his claim. Compare to Hilchot To’en V’Nit’an 11:1.

The Kessef Mishneh quotes two responsa from the Rivash that state that when neither the ownership of a wall nor the identity of the party who built it is known, the fact that one person has many beams inserted into it and the other bas only one or none is not considered proof of ownership.

I.e., if the spaces for the beams were to be hollowed out while the wall was standing, that would shake the wall and make it less sturdy.

In this halachah, the Rambam focuses on the damage that may be caused by the water contained in the cistern. Nevertheless, the actual digging of the cistern may also damage a wall standing next to it, and appropriate precautions must be taken, as explained in Halachah 10.

The latter two terms also refer to types of cisterns. A “trench” refers to a rectangular cistern that is not deep. A “storage vat” refers to a square cistern that is usually decked with a permanent covering.

In his Commentary on the Mishnah (Bava Batra 2:1), the Rambam explains that one might think there is an advantage to a pool for soaking clothes over an irrigation ditch, because there is not always water in the pool, while water is kept in the irrigation ditch on a constant basis. Conversely, one might think that there is an advantage to an irrigation ditch, for there the water is flowing, while in a laundry pool the water remains stationary. Hence, it is necessary to mention both situations.

As the Rambam states in his Commentary on the Mishnah (loc. cit.), laundresses would leave clothes soaking in a vat with various detergents to remove any filth.

This is necessary as a precaution.

See Chapter 10. Halachah 5, where the Rambam states that when a person makes a vat to soak flax near a vegetable garden belonging to a colleague, he must distance his vat by three handbreadths from his colleague’s property. Otherwise, it is as if he damaged his colleague’s property with his own force. Once he makes this separation, any damage that takes place is not his responsibility. In the instance mentioned in our halachah, we must assume that the likelihood of water seeping through the ground and damaging the wall is much greater. Hence, in addition to making the separation of three handbreadths, he must line the wall of the reservoir with cement. (See also the gloss of the Kessef Mishneh on Halachah 10.)

I.e., the remnants of olives after they were pressed for oil.

Our translation follows the standard printed text of the Mishneh Torah. Nevertheless, it is likely that the text is in error and the proper version should be “manure.” This indeed is the text in Bava Batra 2:1 – the source for this halachah – in the Shulchan Aruch (Choshen Mishpat 155:4), as well as in several authoritative manuscripts of the Mishneh Torah.

Our translation is based on the gloss of the Maggid Mishneh, which explains that these stones can cause damage to an adjacent wall.

For these substances can damage the wall, because they generate heat (Sefer Me’irat Einayim 155:16). Nevertheless, the possibility of damage is not as great as exists with regard to water. Hence, only one of the two precautionary measures, making a separation or cement, is required.

I.e., even plants that do not rely on an irrigation ditch (Rambam’s Commentary on the Mishnah, Bava Batra 2:1).
The rationale for this precaution is that plants weaken the structure of the soil and make it more difficult for it to support a wall (Sefer Me’irat Einayim 155:19).

Even plowing for trees (Ibid.). Plowing also weakens the land’s ability to support the wall.

See Halachah 6. It can be explained that in this halachah, the Rambam is speaking about distancing oneself even from a wall of marble. Hence, since we are speaking about a cesspool, and not just urinating once, precautions are necessary.
The Maggid Mishneh questions why a wall is not necessary in this instance, as it is necessary with regard to a pool used to launder clothes. He explains that the laundry pool is used more frequently than a cesspool. Hence, stricter measures are necessary. Note the Ramah (Choslren Mishpat 155:5), who requires that the cesspool be lined with cement.

For the lower millstone is larger than the upper millstone.

I.e., we are afraid that the grinding of the mill will rock the ground and weaken the wall’s foundation (Bava Batra 20b).

Bava Batra 20b states “because of the noise.” Others interpret that to mean that over the course of time, the sound waves may impair the wall’s strength. Indeed, this interpretation is reflected in the Rambam’s own Commentary on the Mishnah (Bava Batra 2:1).
The Ramah (Choshen Mishpat 155:7) states that this applies only to mills that are operated by hand. If, however, the mills are turned by animals, a greater distance must be made between the mill and the wall, because of the damage that might be caused.

For in Talmudic times, the bases of the ovens were wide - to hold the fuel - and their tops narrower (Maggid Mishneh).

And the heat will weaken the wall’s stability.

For the urine will cause the wall to rot.

For it will suffer greater damage from urine than a stone wall.

Where there will be less penetration.

The Maggid Mishneh emphasizes that the Rambam appears to maintain that this is the only instance where a distinction is made between a stone wall and a brick wall. There are, however, other opinions, which maintain that this distinction is made with regard to all – or many – of the factors mentioned above. See Shulchan Aruch (Choshen Mishpat 155:9) and commentaries.

It would appear that even for such a wall, separation would have to be made between a cesspool and the wall (Sefer Me’irat Einayim 155:22). The Tur (Choshen Mishpat 155), however, differs and maintains that the Rambam would allow even a cesspool immediately next to a marble wall.

When a person is setting a ladder down to enable him to climb over a wall to reach his own property from that of a colleague, he must be careful not to place the ladder within four cubits of his colleague’s dovecote.

A small carnivorous animal.
By mentioning “when the ladder is placed down,” the Rambam implies that the person is liable only if the marten jumps from it directly after he placed it down. If he leaves the ladder there and the marten jumps afterwards, his deed is not considered as a direct cause of the damage.

I.e., clear it of the dirt, sticks, and stones that collect there.

The Maggid Mishneh notes that in Chapter 8, Halachah 5, the Rambam writes that a person can build under a drainpipe belonging to a colleague, seemingly contradicting the principle reflected in this halachah. The Maggid Mishneh explains that there is not necessarily a conflict. For by building under a drainpipe one does not necessary restrict access to it. By building next to it, by contrast, one does prevent the owner from setting up a ladder.
The Tur [and his opinion is reflected in the ruling of the Ramah (Choshen Mishpat 155:17)] differs and maintains that the fact that a person has a right to maintain a drainpipe does not grant him the right to prevent his colleague from building there, unless he actually purchases that privilege.

The Rambam states “as a Gam,” referring to the Greek letter gamma written in an inverted L-shape. One might ask: Since the Rambam uses a Hebrew letter in the next line, why did he not say: “As a final chaf”?
The Greek Letter Gamma
Since Reuven’s wall is placed at the side of the wall belonging to Shimon, there is no difficulty. For this does not prevent people from coming and treading on the earth near the wall (Rashi, Bava Batra 22b).

The Maggid Mishneh questions: Why is the owner of the land next to a wall required to leave an empty space of four cubits? He explains that this halachah applies in an instance where both owners purchased their land from the king of the country. Thus, when the king sold the land to Shimon, there was already a binding obligation on that land, not to cause damage to the structures on the neighboring plot. If, however, the land was not purchased in such a manner, one may build a wall next to another wall [Ramah (Choshen Mishpat 155:14)].

This applies in both a new and an old city. Since the earth surrounding the wall of a garden is not pressed down from the inside, it must certainly be pressed down from the outside (Maggid Mishneh).

A city is considered new for 50 years [Ramah (Choshen Mishpat 155:13)].

The Ra’avad comments concerning this law: “It is a nice deduction,” implying that, although there is no explicit source for the Rambam’s ruling, it is logically sound. Nevertheless, according to the text of the passage from Bava Batra possessed by the Ri Migash, the Rambam’s teacher, this concept is obvious from the Talmud itself.

In contrast to Halachah 1, which speaks about the damage that could be done from the water contained in a cistern, this halachah focuses on the possible damage caused by actually digging the cistern.

I.e., the field is located in a place of abundant rainfall, and there is no need to irrigate it employing a cistern.

For it is unlikely that his colleague will dig a cistern there.

As reflected in the Rambam’s Commentary on the Mishnah (Bava Batra 2:1), this distance is a natural consequence of building the cistern. For the wall of a cistern is three handbreadths thick. (See Hilchot Mechirah 21:12.) Thus, there must be a six-handbreadth difference between the cavities of the two cisterns.
There are, however, opinions that do not require a person to build a cement wall within his cistern. Note the Ramah (Choshen Mishpat 155:18), who discusses this issue.
The Maggid Mishneh mentions other opinions (which apparently do not accept the premise that the cistern must have a wall and), which do not require the colleague to separate by more than three handbreadths from the border line when digging his cistern. For he can tell his neighbor: “Is it not enough that you overstepped your privileges by building your own cistern at the border line? Must you also require me to move more than necessary?’’ The Shulchan Aruch (Choshen Mishpat 155:18), however, follows the Rambam’s ruling.

For it is a firm possibility that his colleague will ultimately dig a cistern there (Rambam’s Commentary on the Mishnah, loc. cit.).

This precaution will preserve the six-handbreadth distance between the two cisterns.

Sefer Me’irat Einayim 155:1 states that this applies regardless of whether the opening of the oven is pointed to the side or upwards.

Lest the fire coming from the oven burn the ceiling. We assume that the four cubits of open space will minimize the possibilities of danger.
The Shulchan Aruch (Choshen Mishpat 155:1) rules that every person must leave a similar space between his oven and his ceiling even if no one is dwelling in the second storey, lest his roof take fire and burn down his neighbors’ homes.

For support, lest the weight of the oven cause the ceiling to collapse.

Which is a smaller structure.

Which is larger than an ordinary oven.

Sefer Me’irat Einayim 155:2 states that when the owner of the lower storey builds any of these structures, he must leave a separation of four cubits between the top of the structure and the ceiling.

See Hilchot Nizkei Mammon, Chapter 14.
The commentaries question this ruling, noting that in Halachah 2 of the chapter cited, the Rambam rules that if the person takes the necessary precautions, he is not liable. However, they make a distinction, explaining that lighting a fire outside is not a usual activity. Therefore, if the person took the necessary precautions, but the wind nevertheless carried the fire beyond the person’s property, this is considered a loss beyond his control. With regard to a fire in one’s oven, since this is an ordinary happening, one should supervise it carefully and bear responsibility if a fire occurs (Siftei Cohen 155:2).

This is the rationale for all the prohibitions mentioned in this clause. Although, as will be explained, a barn also has other undesirable factors, e.g., its odor, the Rambam focuses on the drawback that is common to all the points mentioned.

Bava Batra 20b explains that the wine of Eretz Yisrael is stronger than the wines of Babylonia. Therefore, heat will improve its flavor, rather than spoil it. In his Commentary on the Mishnah (Bava Batra 2:3), the Rambam states that this applied in Eretz Yisrael in the era of the Mishnah, but not necessarily at other times and in other places. The laws stated here should be understood as principles to be applied to the particular circumstances that pertain in any given time or place.

For the unpleasant odor of the barn will become attached to the wine. Similarly, if any other factor caused by his activity will spoil the wine, he may not perform that activity. [See Ramah (Choshen Mishpat 155:2).]

For once a person has established the right to perform an activity, even though it may be deemed undesirable, we cannot prevent him from continuing.

To prevent the dust from rising.

As is necessary for a warehouse.

I.e., types of produce that will not be damaged by heat (Sefer Me’irat Einayim 155:10).

Which would be damaged by heat.

I.e., it is his intent to say that the loft will absorb the heat caused by the oven before it reaches the second storey (Sefer Me’irat Einayim 155:11). Note that Rashi (Bava Batra 20b) offers a different interpretation of this clause.

All these situations represent unresolved questions raised by Bava Batra 20b. Accordingly, we rule that because of this lack of clarity, the status quo should be preserved and the owner of the store should be prevented from building the oven.

Since the Talmud did not resolve the doubt concerning these situations, once the owner of the store built his oven, the status quo is in his favor. For the owner of the warehouse has no definite proof that the law supports his position.