The Schach is comprised of detached inedible plant matter which was never susceptible to Tumah.
The Schach should not be prone to excessive shrinkage or leaf shedding, to the degree that insufficient Schach will remain by the end of Sukkos. [If one did not adhere to this, the Sukkah is disqualified from the outset.]
The Schach should not cause discomfort to the Sukkah’s inhabitants, e.g. if it is foul-smelling or sheds leaves constantly. [If one did not adhere to this and the Sukkah is already built, it may be used.]
One should purchase Schach only from a reliable vendor who ensures that there is no concern of Gezel.
It is customary that timber ordinarily used in construction is not used for Schach.
A mat may be used as Schach only if it has been manufactured for shade or fencing, and not for sitting or lying down on.
