If one suspends the walls from above downwards, if [they are] three handbreadths above the ground, it is invalid; from below upwards, if it reaches a height of ten handbreadths from the ground, it is valid.  R’ Yose says: Just as from below upwards ten handbreadths [suffice], so from above downwards ten handbreadths [suffice].  If one moved the s’chach three handbreadths away from the walls, it is invalid.

A house that was breached and he placed s’chach over it, if there are four cubits from the wall to the s’chach, it is invalid. The same [applies to] a courtyard that is surrounded by a portico.  A large succah that they ringed with material that we may not use for s’chach, if there were four cubits beneath it, it is invalid.