Question: I was invited to a friend’s sukka and I noticed that his sechach was tied down with plastic cable ties. Was his sukka kosher?
Answer: The Gemara (Sukka 21b) discusses whether the materials used to support the sechach (maamid) need to be fit for sechach themselves. There is a machlokes rishonim as to what the halacha is. While the Ramban (Milchemes Hashem, Sukka 10a) and Ran (Sukka 10a) write that one can’t use a maamid that wouldn’t be kosher for sechach, the Shulchan Aruch (OC 630:13) paskens that one may (See Beis Yosef OC 630:26). Thus, the Magen Avraham (OC 629:9) and Mishna Berura (629:22) write that while it isn’t ideal to use a non-kosher maamid, if one did use such material to support their sechach, it would be kosher bedieved.
The Shulchan Aruch (OC 629:7) questions whether one may use a wooden ladder as sechach. The Rema writes, therefore, that one shouldn’t even place it on top of their sechach to keep it in place. The Taz (OC 629:10), however, challenges this, as surely the ladder would be rendered insignificant (battul) by the rest of the kosher sechach. The Aruch Hashulchan (OC 629:18) writes that the ladder that the Shulchan Aruch was referring to was a particularly large one with slats that were four tefachim wide. There wouldn’t be an issue, however, with using narrower beams made out of metal, etc.
The Shulchan Aruch (OC 629:5) writes that one may use unprocessed reeds for sechach. The poskim write that materials used to tie the sechach down are also considered to be maamid (See Mishna Berura 629:24). While one can’t nail sechach down (Magen Avraham OC 627:2; Shaar Hatziyun 633:6), the Mishna Berura (629:26) writes that one may use such string to tie down one’s sechach to wooden supports. R’ Ovadia Yosef (Yechave Daas 1:64) allows one to use cotton thread to tie bamboo mats together, especially as such thread is only possul miderabanan as sechach. Seemingly, the Aruch Hashulchan (ibid.) would even permit plastic cable ties lechatchila.
R’ Betzalel Stern (Betzel Hachachma 5:44) writes that if the sechach would be able to stay on with the ties under regular wind conditions, then the sukka would be kosher regardless of what ties it down. If during storm weather the sechach only stays on due to plastic ties, however, then the sukka would be unfit to use during the storm according to some poskim.
In conclusion, it is preferable to use natural unprocessed twine to tie one’s sechach down with. While some poskim would always allow one to use plastic cable ties, there are others that write that one should only do so if the sechach would otherwise stay on under normal wind conditions and it wouldn’t be fit to use under heavy winds.