Eruvin 92 – Two roofs, a large and a small one

If there are two adjoining roofs over two houses, a large one and a small one, then it is permitted to carry on a large one, but it is forbidden to carry on a small one on Shabbat. Why? We need to explain both parts of this rule.

The roofs are not surrounded by walls, or partitions, they are just flat roofs on top of the houses, so how could any roof be considered a private area where it is permitted to carry? We see here a new principle, “extend the wall:” the walls of the houses that go down can be extended up and serve as imaginary partitions surrounding the roof. We understand now why it can be permitted to carry on the large roof.

Furthermore, the small roof is considered simply an opening, a door for the large one, which does not upset its status as a private area. However, the small roof is completely open to the large one. It is not just an opening or a door, it takes away one of the small roof’s wall partitions. The small roof is then like a courtyard with a missing wall, open into the street, and one cannot carry in such a courtyard, and consequently on this small roof, as we have seen at the very beginning of Eruvin.

Art: Roofs at Szentendre 1930s by George Loftus Noyes