1,175. Using Boards as Schach

Hilchos Shofar, Succah v’Lulav 5:7

Boards that are less than four handbreadths wide (about 12”) may be used as schach even if they have been planed. If they are more than four handbreadths wide, they may not be used as schach even if they are unplaned. This is a preventive measure out of concern that one might sit under a roof and treat it like a succah. If board more than four handbreadths wide is placed over a succah, the succah is still valid but one may not sleep under this board. If one did sleep under this board, he does not fulfill his obligation. If there were boards that were four handbreadths wide but they were less than four handbreadths thick, so someone turned them on their edges for use as schach so they would not be four handbreadths wide, it is not valid. This because a board is unfit for use as schach whether one uses its width or its thickness.

Hilchos Shofar, Succah v’Lulav 5:8

If a roof is not covered by a ceiling of plaster and stones, rather it is only boards, it may not be used as schach. This is because the boards were placed there to be part of the house, not to be used for a succah. Therefore, if one raised the boards and removed the nails with the intention to use the boards for a succah, it is valid. Of course, this only applies so long as each board is less than four handbreadths wide (about 12”). Similarly, one may remove a board from between two others and replace it with schach with the intention to use it as a succah.