Case:Neighbors jointly presented an expansion plan for their apartments to the Urban Planning Board and received permission for their building plans. The plaintiffs (=pl) received permission to build rooms totaling 60 square meters. The defendants (=def), who are their upstairs neighbors, asked for permission only to close off a 20 m. balcony and use the roof of pl’s extension for open balconies. Originally, pl and def planned to have their work done jointly, sharing the costs. However, def became short on money and delayed their plans, and pl built on their own and presented def with a bill of 85,000 shekels for their part in the costs. Def paid 19,000 shekels without receiving a waiver for further pay. Years later, just before the permission to build expired, def sold their apartment, and the buyers built immediately. Pl are now suing for the remaining 66,000 shekels. Def responds that their share of the building expenses should not be divided evenly with pl, because pl made more serious use of the building. Furthermore, def didn’t use the building at all, as only the buyers built on the extension. According to the law, pl should also pay def for using more joint area than def did.

[This summary does not explore all elements of the ruling.]
Ruling:There are two possible reasons for def to be obligated to share in building expenses. The first is based on agreement, but that does not apply in this case. Although they planned to build together, there was never a commitment to do so, nor was there a serious discussion about apportioning expenses. Pl thus had no ability or right to force def to build with them.
The second possibility is based on the concept that one who benefits due to his counterpart has to pay for the benefit unless it is waived. If one built a wall between his and his neighbor’s properties higher than halacha requires, the neighbor has to chip in toward the extra building if he built his other walls to this height (Bava Batra 5a).
Acharonim ask why when he shows that he enjoyed the building, he is obligated, in light of the halacha that when one takes benefit from another party who does not lose as a result, the one who benefits does not have to pay (see Bava Kama 20b). The K’tzot Hachohen (158:6) explains that when the neighbor shows he likes the wall, he turns into a partner in the wall, and then he is obligated to pay as one who so-to-speak bought part of the builder’s wall. The Maharam MiRotenberg (IV:685) that the halacha that one who benefits does not have to pay is only when his presence is beneficial for the person who provided the benefit. Otherwise, there is a natural obligation to pay for the benefit.
According to the latter opinion, while having a second floor on top of pl’s extension protects pl’s rooms from leaks and cold, overall most people prefer to not have neighbors on top of their heads. Therefore, it is likely that the Maharam would require payment.
[We will continue from here next time.]