Daf Yomi - Sukkah 21 - Supports for the S'chach

The Gemara states that one should not support the s’chach with something that is susceptible to tumah. Since many people are currently engaged in constructing their Sukkah, it would be appropriate to mention some of the halachos pertaining to the support for the s’chach. These halachos are quoted with sources in the Sefer Nitei Gavriel from Rav Gavriel Zinner. Shulchan Aruch Orach Chaim 629 rules that it is preferable not to place the s’chach on something which is susceptible to tumah. It is also preferable that one should not place something which is susceptible to tumah on top of the s’chach in order that the s’chach should not scatter or fall. This issue was discussed previously on Daf 13 regarding kernels of grain here. This Halacha is true even if it is only rabbinically susceptible to tumah.There are authorities who maintain that the supporting beams for the s’chach should not be more than four tefachim wide whereas other opinions maintain that this is not a necessary requirement. One is allowed to place the s’chach directly on a stone wall but some opinions rule stringently and maintain that one should place reeds on top of the wall under the s’chach. Most halachic authorities rule that one does not have to be particular regarding the supports for the supporting beams of the s’chach. The Pri Megadim, however, rules that one should not attach his supports to the Sukkah with nails and pegs in a manner that without those supports the boards would fall. The Chazon Ish rules similarly. If one would use screws in order that the beams should not move from their positions, this would not be a concern.Even if one supports the s’chach with something that is susceptible to tumah, and certainly if he has no other option, it does not invalidate the Sukkah.

I noticed this halachic article pertaining to a canvas sukkah and regarding supporting the s'chach and I think it is worth looking at.