Sukkot - When Schach Falls Off

What can you do if your schach fell off on Shabbat or Yom Tov?

According to the Mishna Berura [Orech Chaim 737 note 1] if schach fell off of a sukkah on Yom Tov and rendered the sukkah is unusable, it is permitted to ask a non-Jew replace the schach. Yet, if the schach fell off on Shabbat, the Mishna Berura would prohibit replacing it.

However, the Pri Megadim disagreed, and would allow replacing the schach, on both Yom Tov and Shabbat [Eshel Avraham 737 note 8]. In fact, this is precisely what happened to Rabbi Yosef Teumim (the "Pri Megadim") during the holiday Sukkot in 1866 - and his family arranged for a non-Jew to replace the schach [cf. HaSukkah HaShalem Addendum to Chapter 17 paragraph 4].

Of course, this only applies to a situation where the sukkah had already been completed and then suffered damage. However, if the schach had not been place on the sukkah in advance of the holiday it is prohibited to have a non-Jew to put schach on and complete the sukkah [Mishna Berura 726 note 20]