Baba Basra 1:3-4

Baba Basra 1:3

If one person’s property surrounds that of another person on three sides and he erected a fence on all three sides, the other party is not compelled to contribute. R. Yosi says that if the second person fences off the fourth side of his property, then he must contribute to the cost of fencing the first three sides as well.

Baba Basra 1 4

If the wall of a courtyard collapses, the partners can be compelled to rebuild it to a height of four cubits (about six feet). The assumption is that a partner has paid his share unless the other party provides proof to the contrary. One is not compelled to build higher than four cubits. If one of the parties builds another wall close to the first, we compel him to contribute towards the first even if he did not yet build a roof connecting the two walls. The assumption in such a case is that he did not yet pay unless he brings proof that he did.

Hear Rabbi Novak's original shiur here.