[If] a ground floor and an upper story belonging to two [people] collapsed, [and] the owner of the upper story demanded of the owner of the ground floor that he rebuild, but he refuses —- the owner of the upper story may rebuild the ground floor, and live in it until he reimburses him. R’ Yehudah says: Even this one [who] lives in his neighbor’s property must pay him rent. Rather, the owner of the upper story rebuilds [both] the ground floor and the upper story, and puts a roof on the up-per story, and lives in the ground floor until he reimburses him.