The STAR-K currently certifies schach made from bamboo slats held together with monofilament type cord for use during Sukkos. The following is an explanation of the psak of Rabbi Moshe Heinemann regarding this item:
In Hilchos Sukkah (Shulchan Aruch, Orach Chaim 629:1) it is written that schach can not consist of something that is “mekabel tumah” (something that has the ability to become ritually impure). It is for this reason that bamboo carpet mats cannot be used for schach as they are mekabel tumah. All Star-K certified schach is not made to sit or walk on and is therefore not mekabel tumah.
In addition, l’chatchila, kosher schach may not be supported by anything which is mekabel tumah (see Rama O.C. 629:7). According to the opinion of Rashi (as brought in Shaar Hatziyun 629:20) spun or woven threads (e.g. string, yarn) are mekabel tumah. Rav Moshe Feinstein states (Igros Moshe, O.C. 1:177) based on a Mishna, if something which is mekabel tumah is used to hold wooden slats together, the slats themselves are also mekabel tumah and are no longer kosher for schach use. Therefore, Rav Moshe Feinstein explains that wooden venetian blinds held together with cloth tape or string are not kosher for schach. It follows that according to Rashi bamboo slats held together by multi-filament cord (i.e. it is braided or twisted) are also not kosher for schach (even if they are not made to sit or walk on).
However, monofilament (commonly used for fishing line) is not woven or spun material. Therefore, it is not mekabel tumah and may be used to hold bamboo slats together. All Star-K certified bamboo schach is held together with monofilament cord.
When placing the schach mat on the Sukkah – The following guidelines should be followed:
- The bamboo slats should be resting perpendicular to the beams and walls upon which they are set.The reason is as follows: If the slats are resting parallel to the walls and beams upon which they are set, the middle slats will be suspended only by the monofilament. One may not suspend schach with non-schach material. Although monofilament is not mekabel tumah and will not invalidate kosher schach, it cannot serve as schach and cannot support the schach (see B’aer Haytav 629:8).
- If a normal prevailing wind (ruach metzuya) can blow the schach off the sukkah, one may not tie the schach down to hold it in place. The reason is that an item which is not kosher for schach (e.g. string) may not be used to hold down kosher schach. Instead, one must place a wooden beam (e.g. 2×4) on top of the schach which is resting on the walls thereby sandwiching the schach between the beam and the top of the walls. This beam should be placed perpendicular to the bamboo sticks, so that the beam would hold down the sticks without the presence of the fishing wire. Once this is done, one may then tie a string around the schach to anchor and protect it from falling off in a gusting wind (ruach she’ayna metzuya).
- As with all schach, Star-K certified schach may also not be placed directly on top of metal. If one has a metal frame one should cover the frame with wooden slats and place the schach on top of the these slats.