Mr. Adler and Mr. Braun shared a small two-story building. The Adlers occupied the lower floor, and the Brauns lived above them, on the second floor.
One evening Mr. Adler came up holding architectural plans. “I’d like to submit a zoning request to add a room to my apartment in the backyard,” he said. “If you agree, you could extend a room on top. Otherwise, you might want to consider opening a doorway and using the roof of the added room as a porch.”
“Let me consider the issue with my wife,” said Mr. Braun.
The following day Mr. Braun told Mr. Adler, “We’re not in a position to build on top, but the porch option sounds like a good idea for the future. I assume this has to be factored in to the architectural planning, and may entail certain additional costs.”
“Of course,” replied Mr. Adler. “I’ll have to make a flat roof. Instead of simply waterproofing with tarpaper, you also might want a proper floor laid on the roof to be comfortable. It would then be perfect for a sukkah. I’ll check with the contractor what the differential in cost is.”
Mr. Adler consulted the contractor and came back with a figure of the extra cost to build the roof usable for a porch. Mr. Braun agreed to chip in this sum.
Mr. Adler built the additional room, with the roof potentially usable as a porch for the Brauns. Three months after the construction was completed, Mr. Braun had the contractor break his outside wall and build a doorway to the porch.
Mr. Braun then turned to Mr. Adler. “There is a mitzvah of ma’akeh, to build a guardrail around one’s roof,” he said. “The Torah states in Parshat Ki-Teitzei: ‘If you build a new house, you shall make a fence for your roof. I think it’s your responsibility.”
“I don’t think the mitzvah applies to me,” objected Mr. Braun. “The pasuk refers to a roof that is used. I don’t use the roof at all and don’t even have access to it. If anyone is responsible to build a ma’akeh, you are!”
“I don’t think so,” replied Mr. Adler. “The verse clearly states, “If you build a new house, you shall make a fence for your roof. It’s your house, so you should be responsible to build the guardrail!”
“Let’s consult with Rabbi Dayan,” suggested Mr. Adler.
The two met with Rabbi Dayan and posed their question.
“A similar question was raised almost 500 years ago,” Rabbi Dayan said. “Someone rented out the rights of his roof to another person for laundry and recreation. The Mabit, R. Moshe b. Trani, asked his teacher, R. Yosef Karo, author of the Shulchan Aruch, whether there was an obligation of ma’akeh, and if yes, who is obligated?” (Mabit 1:110)
“What did R. Yosef Karo answer?” asked Mr. Adler.
“His answer is somewhat cryptic,” replied Rabbi Dayan. “Rav Karo answered that there would not seem to be an obligation of ma’akeh, since the obligation of ma’akeh is only on the roof of a dwelling house, and here there is no dwelling usage. He adds that if there is an obligation, because of the house below, the one using the roof is obligated, as the Gemara states that the tenant is obligated in the ma’akeh.”
“What does this mean?” asked Mr. Adler.
“He takes for granted that the lower dweller has no obligation, even though it’s his roof, since he has no use of it,” explained Rabbi Dayan. “The only question relates to the upper dweller, who uses the roof. Some authorities understood that Rav Karo remained in doubt as to whether there is need for a ma’akeh. [See Chasam Sofer Y.D. 98; Chazon Ish C.M. Likutim 18:7] Others, though, understood the conclusion of R. Yosef Karo to be definitive, that the renter is obligated.” (Knesses Hagedola II C.M. 226:11)