Related על מעשרות 3:5

Rabbi Shimon ben Elazar says in the name of Rabbi Akiva, any [courtyard] that one opens and another closes, such as two joined [courtyards] with two [different] occupants, the roofs are exempt, even if they are [located] within a courtyard that is liable. (Maasr. 3:5.) [In such a case,] they may ascend to the top of the roof and eat.