Sukkot - Tying Schach

Can Schach Be Tied Down?

In a case when one's schach is very light and is easily blown off of the top of a sukkah, one may tie the schach in place with a material that could, itself, be used for schach (e.g. a simple natural twine) [Mishna Berura 629 note 26]. However, "b'dieved" if another material was used, whether natural or synthetic, the schach is still valid. An exception to this would be if a person attached the schach with nails. In such a case, the schach would be invalid since the roof has been transformed into a "permanent structure" [Magen Avraham 627 note 2; Shaar HaTziyun 633 note 6; However, Aruch HaShulchan 629:19 is more lenient].

However, if the schach does not blow off in a normal wind, but only with a very strong wind, any material (except nails) may be used to tie the schach in place [Responsa B'tzel HaChochma 5:44].