Property
Question
When our building was built each apartment was given an open porch where the owner could build a succa. The way the house was built, when it rained the rainwater from my neighbor (who lives half a flight above me) would fall onto my porch from which it drained to the sewer. In the past this did not bother me because when it rained my porch was anyway not usable. However, now that I enclosed my porch, his rainwater will damage my enclosure. I asked my neighbor to enclose his porch but he refused saying that he doesn't need it and he doesn't have extra money. He agreed to let me build a roof on his porch but refuses to pay anything for it. Can I force him to share in the expense now and if not, if he eventually encloses his porch and uses the roof that I built, will I then be able to force him to share the expense?
Answer
In order to answer the first question, it is necessary to introduce the concept known as chezkas tashmishim. This concept is that a person can establish a right to use another person's property. For example, the Mishna (BB 58B) writes that a person can establish a right to lean his ladder on his neighbor's wall. Once one establishes a right, the owner of the property cannot do anything to hinder the owner of the right from fully utilizing his right.
The Gemara (BB 6A) states that one of the uses of another person's property that a person can establish is the right to drain his rainwater onto the other person's property. The Ramo (153, 12) rules that if A established the right to have the rainwater from his roof drain onto his neighbor B's roof, B may not build on his roof unless he makes an arrangement that will allow A to continue draining his rainwater onto his property.
There is a major dispute among the Rishonim whether one must get express permission from his neighbor in order to establish this right. The opinion of the Rambam and many poskim – and this is the ruling of the SA (153, 2) – is that if A merely starting using B's property in a manner that was clearly noticeable to B and B did not object, A thereby establishes his right to use B's property perpetually.
The opinion of Tosafos and many others is that A cannot establish this right by merely using B's property. A can only establish this right with the express consent of B. The only way in which A's usage with B's silent acquiescence is of help is that it serves as evidence that B gave express permission to A to use his property. Furthermore, according to this opinion it takes three years of use in order to for A to establish that B granted him express permission to use his property. Whereas, the SA is certain that the Rambam's position is authoritative, the Ramo rules that the issue remains undecided.
In your situation, since your house was built in a way that your neighbor's rainwater drained onto your balcony, even the Ramo agrees that your neighbor owns the right to have his rain water drain onto your balcony. The reason is because both you and your neighbor directly or indirectly bought your apartments from the builder. Therefore, when you bought your apartment, you acquired it with the proviso that your neighbor has the right to drain his rainwater onto your property.
Thus, we have established that disposal of your neighbor's rainwater is your problem. Furthermore, even though originally his rainwater did not disturb you, he does not have to find alternative means of disposal after it began damaging you, just like the ruling of the Ramo that we cited previously, that a neighbor could not build on his roof unless he found alternative means to dispose of his neighbor's rainwater. Since the problem is exclusively yours, you cannot force your neighbor to participate in the cost of covering his balcony, since it is you, and not he who needs it.
Your second question is whether in case your neighbor eventually encloses his porch and uses the roof that you built, he will need to share with you the expense of building the roof.
Before answering your question, it is important to understand the issue that is involved. The reason why one may think that your neighbor is not obligated to pay is because he can argue that when he builds, he is benefiting from your roof without causing you any (new) expense, what is called in the Gemara (e.g., BK 20B) ze nehene veze lo choseir. When one benefits without causing his benefactor any loss, the beneficiary is not liable. Thus, it seems that your neighbor will not have to reimburse you even if he later uses the roof that you built.
However, the Mishna (BB 5A) discusses a case that is analogous to your situation. The case discussed by the Mishna concerns two neighbors who by Talmudic law are required to construct a four amos (about two meters) high wall in order to prevent each other from looking into his neighbor's property (hezek re'iyo). In the case discussed by the Mishna, neighbor A wanted to build even higher than four amos but neighbor B did not want to share in the expense, claiming that he had no need for a higher wall. Since A could not force B to share in the expense, A paid for the vertical extension of the wall by himself.
The Mishna rules that if at some later date, B decides to build on his property and wishes to rest his ceiling beams on the dividing wall, he must pay A for using his extension. Thus, we see that we don't view this as ze nehene veze lo choseir.
The Rishonim offer several approaches to explain why B is required to pay. If we follow any of these approaches your neighbor will be required to reimburse you if he encloses his porch and uses the roof that you built as his roof. One approach of Tosafos (BB 5A) is that since B was the original cause that A spent money to build above four amos, we view this situation as ze nehene veze choseir since we combine A's original loss with B's present benefit. If we apply this to your situation, since your neighbor caused you to spend money to build the roof, we view the benefit he has from using the roof that you built as ze nehene veze choseir and he will need to reimburse you.
Another approach of Tosafos is that the only reason B did not have to pay originally is because he claimed that he would not spend money to raise the height of the wall. However, by spending money on beams that rest on the wall he shows that he would spend money on the extension of the wall and therefore, he must pay for it. This will apply in your situation as well since when your neighbor will spend money on enclosing his porch, he will thereby show that he is willing to spend money on the enclosure of his porch, including the ceiling that you constructed.
A third approach (Magid Mishne, Shecheinim 3, 4) is that when A raised the height of the wall, he built it with the intention that B will eventually use it as well. When B begins using the wall he will be forced to partner with A since otherwise A who owns the wall can prevent him from using his wall. In your case as well, since in order to use your roof, your neighbor will need to become your partner, he will have to pay you for his share of the ceiling.
Having established that your neighbor will have to pay you for the ceiling, we have to determine how much he will have to pay you.
The case in the Gemara where this issue is addressed is where A had a large field and B had a small field that was entirely enclosed within A's field. A constructed a wall around his field in order to keep out intruders. Since B benefits from this wall, he must share in the cost of the wall since, because of his field, A had to spend more to enclose his field, due to the larger perimeter.
The consensus (see Mishpatei Yosher vol. 2 page 255) opinion is that the entire cost of constructing is pro-rated based on the relative benefit that each owner had from the wall. Thus, if 60% of the area that was enclosed by the wall belongs to A and only 40% belongs to B, A must pay 60% of the cost of the wall and B pays 40%.
In your situation you and your neighbor will need to split the cost of the ceiling based on the relative benefit that each of you has from the presence of the ceiling. In practice it will be very difficult to determine precisely the relative benefit that each of you will have but you can safely assume that your neighbor will have at least as much benefit as you do since without the ceiling it will rain into his extension whereas for you the ceiling only prevents water from coming onto your external walls. Therefore, beis din could safely require your neighbor to reimburse you for half of your cost.
In conclusion: At present you cannot force your neighbor to share in the cost of the roof that you built. If your neighbor ever encloses his porch and uses the roof that you built, he will have to reimburse you for half of your cost.
