Talmud - Bava Batra 6b בבא בתרא ו׳ ב׳

in a large building with many residences, the renter may make use of the building’s projections and of the cavities in its external walls up to a distance of four cubits from his room, and he may make use of the thickness of the wall in a place where it is customary to do so. But as for making use of the building’s front garden [betarbatz], he may not do so. And Rav Naḥman himself said: He may make use of even the building’s front garden. But he may not use the yard that is at the back of the house. And Rava said: He may use even the yard that is at the back of the house.

Apropos the use of a wall between neighbors, Ravina says: If one’s beam supporting a covering for shade was resting on his neighbor’s wall for up to thirty days, there is no acquired privilege for him to continue using it, since the neighbor can claim that he had assumed that the beam was there only temporarily and for that reason he did not protest. But after thirty days, there is an acquired privilege. And if it was for a sukka that was being used for the mitzva on the festival of Sukkot, for up to seven days there is no acquired privilege for him to continue using it, since it is assumed that it is there for the mitzva and that after the Festival it will be removed. But if after seven days the neighbor did not protest, there is an acquired privilege for him to continue using it. And if the one using the beam attached it with clay, there is immediately such an acquired privilege.

§ Abaye says: If there were two houses on two sides of a public domain, this one, the owner of one of the houses, must build a fence for half his roof, and that one, the owner of the other house, must build a fence for half his roof. They must position the fences so that one fence is not opposite the other fence, and each one must add to his fence a little beyond the midway point, so that each one should not be able to see the activity on the other’s roof.

The Gemara asks: Why discuss specifically the case of two houses on opposite sides of a public domain, considering that the same halakha should apply even if the two houses are separated by a private domain? The Gemara answers: It was necessary for Abaye to mention a public domain, lest you say that one neighbor can say to the other: Ultimately, you need to conceal yourself from people in the public domain. Since in any event you have to build a fence across your entire roof, you cannot compel me to build a fence on my roof.

To counter this, Abaye teaches us that this is not so, because the second homeowner can say to the first in response: The public can see me only during the day, when pedestrians pass by, but they cannot see me at night. You, by contrast, can see me both during the day and at night. Alternatively, he can say: The public can see me from the street only when I am standing, but they cannot see me when I am sitting. You, by contrast, can see me both when I am standing and when I am sitting. And furthermore, the public can see me only when they look specifically at me, but they cannot see me when they do not look specifically at me, since the average pedestrian does not look up to see what is happening on the roofs. You, by contrast, can see me in any case, because you live opposite me.

The Master, i.e., Abaye, said above: This one, the owner of one of the houses, must build a fence for half his roof, and that one, the owner of the other house, must build a fence for half his roof. They must position the fences so that one fence is not opposite the other fence, and each one must add to his fence a little beyond the midway point. The Gemara asks: Isn’t it obvious that each one must make a fence for half his roof?

The Gemara answers: No, it is necessary in a case where one of them went ahead on his own and constructed a fence on half his roof, lest you say that the other can say to him: Take from me compensation for the expenditure [uzinka], and you build the entire fence, and in that way we will not invade one another’s privacy. Therefore, Abaye teaches us that the neighbor who built the fence for half his roof can say to him: What is the reason you do not want to build a fence? It is because the added weight will damage your house’s foundation. My foundation too will be damaged if I continue to build on my roof.

Rav Naḥman says that Shmuel says: If one’s roof is adjacent to his neighbor’s courtyard, he must build a fence on the roof four cubits high, so that he will not be able to see into his neighbor’s courtyard, but he is not required to build a fence between one roof and another roof. And Rav Naḥman himself says: He is not required to build a fence four cubits high on the roof, but he is required to build a partition that is ten handbreadths high.

The Gemara asks: For what purpose, according to Rav Naḥman, does the neighbor have to build such a partition? If it is to prevent damage caused by exposure to the sight of others, we require a partition of four cubits. If it is to catch the neighbor as a thief, i.e., to set a boundary between the two properties so that any trespass will be construed as attempted theft, a mere partition of pegs suffices. And if it is to prevent kid goats and lambs from crossing from one roof to the other, a low partition that is high enough so that the goat or lamb will not be able to leap headlong from one roof to the other suffices. The Gemara answers: Actually, it is built to catch the neighbor as a thief. With a partition of pegs he can give an excuse and say that he was merely stretching himself, but with a partition of ten handbreadths he cannot give such an excuse.

The Gemara raises an objection to the opinion of Rav Naḥman from a baraita: If his courtyard was higher than the other’s roof, he is not required to attend to it. What, is it not teaching that he is not required to attend to it at all, i.e., that he need not build any type of fence? The Gemara answers: No, it means that he is not required to attend to building a partition of four cubits, but he must attend to building a partition of ten handbreadths, as maintained by Rav Naḥman.

It was stated that amora’im disagree about the following case: If there are two adjoining courtyards, one higher than the other, Rav Huna says that the owner of the lower courtyard builds the wall separating the courtyards from his level and upward, and the owner of the upper courtyard builds the wall from his level and upward. And Rav Ḥisda says: The owner of the upper courtyard assists the owner of the lower courtyard and builds from below, even including that part of the wall which is opposite the lower courtyard.

The Gemara notes that it is taught in a baraita in accordance with the opinion of Rav Ḥisda: If there were two adjoining courtyards, one higher than the other, the owner of the upper courtyard cannot say: I will build from my level and upward, but rather he assists the owner of the lower courtyard and builds from below. And if his courtyard is higher than the roof of his neighbor, he is not required to attend to it. The owner of the upper courtyard need not build a partition because people do not ordinarily use their roofs.

§ It is related that two people were living in a two-story building; one was living in the upper story, and one was living in the lower one. The lower story began to collapse, its walls sinking into the ground to the point that it was no longer fit for dwelling. The owner of the lower story said to the owner of the upper story: Come and let us demolish the whole building and rebuild it together. The owner of the upper story said to him: I am living comfortably and am under no obligation to rebuild your residence.

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

BavaBatra 6b explores shared-wall usage rights between renters and neighbors, plus rules on acquiring privileges through beams, sukkot, and rooftop fences.