Mr. Adler and Mr. Braun shared a small two-story building. The Adlers occupied the lower floor, and the Brauns lived on the second floor.

One evening Mr. Adler came up holding architectural plans. “I’m planning to add a room to my apartment,” he said. “You can extend a room on top. Otherwise you might want to use the roof of the added room as a porch.”

“We’re not in a position to build on top,” said Mr. Braun, “but the porch option sounds like a good idea. I assume this has to be factored in to the architectural planning.”

“Of course,” replied Mr. Adler. “I’ll have to make a flat roof. Also, instead of simply waterproofing with tar paper, you would 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 cost differential is.”

Mr. Adler gave Mr. Braun a figure of the extra cost for building the roof so it could be used for a porch, which he agreed to pay.

After the construction was completed, Mr. Braun opened a doorway to the porch.

Mr. Braun then turned to Mr. Adler. “There is a mitzvah of maakeh, to build a guardrail around one’s roof,” he said. “I think it’s your responsibility.”

“The passuk refers to a roof that is used,” objected Mr. Braun. “I don’t use the roof at all and don’t even have access to it! If anyone is responsible to build a maakeh, you are!”

“I don’t think so,” replied Mr. Adler. “The passuk clearly states: ‘If you build a new house, you shall make a guardrail for your roof’ (Devarim 22:8). 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 to his roof to another person for laundry and recreation. The Mabit, Rabi Moshe ben Trani, asked Rabi Yosef Karo, mechaber of the Shulchan Aruch, whether there was an obligation of maakeh, and if so, who is obligated” (Mabit 1:110).

“What did Rabi Yosef Karo answer?” asked Mr. Adler.

“His answer is somewhat unclear,” replied Rabbi Dayan. “He answered that there would not seem to be an obligation of maakeh, since the obligation of maakeh is only on the roof of a dwelling, and in this case no one lived there. He adds that if there is an obligation because of the apartment below, the tenant using the roof is obligated” (See B.M. 101b).

“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 Rabi Karo remained in doubt whether there is need for a maakeh. (See Chasam Sofer  OC.52, Y.D. 280; Chazon Ish C.M. Likutim 18:7.) Others, though, understood the conclusion of Rabi Yosef Karo to be definitive: that the renter is obligated” (Knesses Hagedolah II C.M. 426:11).

“Thus, in our case, the upper dweller would have to build a maakeh, since there is a safek d’Oraisa,” added Rabbi Dayan. “Moreover, even if there is not an actual obligation of maakeh, the mitzvah is extended to remove any potential danger (C.M. 426:7-8). If it is not a definitive mitzvah, though, there is no brachah on building the guardrail.”

“Our case is not exactly a renter,” noted Mr. Adler. “We agreed that Mr. Braun owns the porch.”

“That is a valid point,” replied Rabbi Dayan. “Some contemporary authorities write that even if a renter is exempt, where the upper dweller owns the roof porch he is certainly obligated in maakeh and needs to make a brachah.”

“Who would make a brachah, anyway, considering that the contractor building the guardrail is not Jewish?” asked Mr. Adler.

“Let’s leave that for our next discussion,” concluded Rabbi Dayan.