Mr. Waltuch and Mr. Hauser owned adjacent properties; relations between them were not great. A tall, dividing wall stood between their properties.
One day, Mr. Waltuch decided to build a garage in his property adjacent to the wall. He propped the roof beams for the garage on the wall, across its full thickness.
Mr. Hauser saw the beams lying on the wall. “What are those beams doing on my wall?” he asked Mr. Waltuch. “I also own the wall, and I don’t permit you to place your beams on it.”
“We share the wall,” pointed out Mr. Waltuch, “so I have rights to use it. An engineer confirmed that the beams will not damage the wall.”
“If we share the wall, that means half is mine and half is yours,” said Mr. Hauser. “At most, you can prop the beams on your half of the wall, but not on my half!”
“I suggest we discuss the issue with Rabbi Dayan,” said Mr. Waltuch.
After listening to both parties, Rabbi Dayan said, “The Mishnah [Bava Basra 2a] teaches that neighbors can require each other to build a dividing wall between their properties; the cost of construction and the thickness of the wall is split between the two neighbors.” [C.M. 157:3]
“Can each party use the wall as he sees fit?” asked Mr. Hauser.
“The Tur cites a seeming dispute on this issue,” replied Rabbi Dayan. “If one party wants to raise the height of the wall at his own expense, some Rishonim allow him to do so since each party has rights to the entire wall. The Rosh, however, maintains that the other party can object and claim that half of the wall’s thickness is his.” [Tur and Bach, Choshen Mispat 157:26; see Ketzos 157:5,10]
“What does the Shulchan Aruch say?” asked Mr. Waltuch.
“The Shulchan Aruch [Choshen Mishpat 157:9] cites both opinions, but doesn’t come to a definitive decision,” answered Rabbi Dayan. “The Achronim discuss who is considered in possession [muchzak] in such a case, also without clear resolution.” [Ba’i Chayai Choshen Mishpat 1:91]
“The Gra links this dispute to a dispute between Rav and Shmuel in the Yerushalmi [Bava Metzia 10:6] on whether the wall belongs half to each or entirely to each,” continued Rabbi Dayan. “He points out that the Shulchan Aruch, in another place, seemingly rules that each side can use the entire wall.” [Gra 157:41; Choshen Mishpat 154:26]
“Where does this leave us?” asked Mr. Hauser.
“The halacha is not conclusive, but tends towards allowing Mr. Waltuch to utilize the wall’s entire thickness,” replied Rabbi Dayan. “Regardless, local law usually forms a common practice. In most law codes, each party owns the part of the wall sitting on his property. Some places grant each person the right to use also the other half (easement), while others do not.”