S'chach

[2] The s'chach must be made from plants, i.e., materials grown from the ground, such as palm leaves, bamboo sticks and pine tree branches.

[5] The s'chach must rest on top of the sukkah without being tied down to the structure itself.

Similarly, while one can re-use a sukkah, the s'chach must be replaced each year.

This does not mean one must build it from scratch but, at a minimum, the s'chach must be lifted off of the sukkah and then put back in place.

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