Yerushalmi Bava Batra 3:10 ירושלמי בבא בתרא ג׳:י׳

MISHNAH: A person may not open windows into the common courtyard¹³⁶Once the house is built, nobody may make any changes to his house which infringes on the privacy rights of the co-owners without the explicit agreement of all co-owners. In particular one may not add windows which would enable him to see activities of his neighbors which he could not see without them.. If he bought a house in another courtyard he may not open it into the common courtyard¹³⁷If he bought a house whose back wall borders on the condominium courtyard where his other house stands, he may not open a door directly from the common courtyard into that house since the door would acquire rights to the four adjacent cubits to the detriment of the other owners and increase traffic in the courtyard. If he wants to build such a door, he must buy the building rights from his co-owners.. If he built a second floor on top of his house he may not open it into the common courtyard but he may build a room inside his house or a second floor on top of his house on condition that the access to it be from within his house¹³⁵It seems that this sentence belongs to the next Halakhah, where it is explained that a person may transform a one-family house into a multi-family one as long as he constructs an interior staircase and does not increase the number of doors leading from the house into the courtyard..
In a common courtyard a person may not open a door opposite a door, a window opposite a window. If it was small, he may not enlarge it. If it was one, he may not make it double¹³⁸All these activities allow him to see more of his neighbors’ activities.. But he may open into the public domain a door opposite a door and a window opposite a window. If it was small, he may enlarge it. If it was one, he may make it double¹³⁹Since building a door or a window open towards the public domain implies a waiver of privacy rights..

HALAKHAH: “A person may not open windows,” etc. ¹⁴⁰The following explanation is based on Rashba, Responsa vol. 5, #106. Here you say, a door opposite a door is permitted, and there you say, a door opposite a door is forbidden¹⁴¹The Mishnah forbids making doors opposite doors in a courtyard but allows them on a public street. It does not say anything about an alley, a narrow dead-end street frequented only by the inhabitants of the courtyards opening into the alley and their visitors, and usually bordered by windowless walls. The status of the alley is not defined in the Mishnah. If opposite doors only be forbidden in a courtyard, they would be allowed in an alley; if they only be allowed in a thoroughfare they would be forbidden in an alley.. Where you say it is permitted, in an alley¹⁴²The alley is part of the public domain.. And where you say it is forbidden, in a condominium courtyard. But did we not state¹⁴³Tosephta 2:15.: “Just as the inhabitants of a courtyard may object to one another, so the inhabitants of an alley may object to one another”? Rebbi La said, here when permission was given, there when permission was not given¹⁴⁴In principle, R. La accepts the explanation given earlier but he holds that for opening a door directly into the alley one needs the agreement of the other inhabitants of the alley. This agreement, once given, is irrevocable. But in a courtyard any co-owner may retract his assent at any time since according to the Mishnah the door should not have been built in the first place.. Rebbi Joḥanan said, there is a difference because gardens are usually dug into¹⁴⁵This is the text of L. It does not refer to the question raised in the text but to a later statement in the same Tosephta, that if a brook passes through somebody’s vegetable garden, he may divert its water at will for his irrigation needs. This seems to contradict the entire tenor of the present Chapter which denies the individual the right to infringe upon pre-existing rights of others. R. Joḥanan holds that if the brook was treated as private property, in that the farmer’s lot was taxed as one vegetable garden rather than two properties separated by a river, the owner must be permitted to use his property without restriction.
E reads here: שַׁנְייָא בַּגַּגּוֹת שֶׁנִּיתְּנוּ לְהַפְרִיח “there is a difference because roofs are usually made to protrude.” That would refer to Halakhah 9 (Note 133) but probably is a corruption.. Rebbi Nasa said, are ruins not to be rebuilt¹⁴⁶Sometimes the door built later forces a door built earlier to be walled up. If an earlier house collapsed, its right to have a door into the courtyard has not disappeared; no door can be built opposite the future door of a rebuilt house.?

Rebbi Jacob bar Aḥa said that there¹⁴⁷In Babylonia., one states: If somebody opens a window in the wall of somebody else’s courtyard in the presence of the other (four cubits)¹⁴⁸Reading of L, a corruption., [Rebbi says]¹⁴⁹Reading of E, accepted as correct. he takes down^149*Perhaps one should read פותח “he opens” instead of פוחת “he takes down”. with his left hand and closes with his right¹⁵⁰He has to wall it up again faster than he opened it. The wall’s owner retains an unconditional right to demand the walling up of the window.. Think of it, was he not standing there? He may tell him, I wanted to enjoy myself. If he handed him stones¹⁵¹Helping with building material.? He may tell him, I was making fun of this¹⁵²Reading בָּאוּ (vocalization of the ms.) as בְּהַהוּא (S. Lieberman, Tarbiz 5, 1934, pp. 100–101.) man.

If there were five openings one inside another, the measure of all of them is a drill hole. This supports what the builders say, viz., that a window open above a stone bench¹⁵³Which is inconvenient to reach. is made only to let light in. Since it cannot represent a right of possession, it cannot bring impurity¹⁵⁴This is rather elliptic; it refers to the rules of impurity of the dead, the most important rule of which is that any person or vessels under one “tent” with a corpse becomes impure. If the corpse is in a stoa of which a wall belongs to a house, any window in that wall brings the impurity into the entire house. Mishnah Ahilut 13:1 states that if the window was made for light only, the minimal size which makes it a conduit of impurity is the size of the drill-hole of a builder’s drill, which in Kelim 17:12 is said to be equal to the size of a Neronian tetradrachma or a circular disk of about 25mm diameter. A window made for use to bring vessels to or from the building must be at least one handbreadth square; for people it must let a person crawl through. Since five successive windows of minimal size do not let light in, they are not made for light and do not transmit impurity. Then it is stated that a window which does not transmit impurity is an Egyptian window which cannot represent a right of possession (J. Benvenisti in Śede Yehoshua.).