If the walls of the succa are suspended 3 tefachim off the ground, the wall is posul. If the wall starts from the ground and is ten tefachim high it is kosher. R’ Yosee says a wall of 10 tefachim is kosher even if it hangs high off the ground.

Succa 1:10

If the roof of a house got a hole in it, and the hole starts less than 4 amos from the wall of the house and you cover the hole with kosher sechach, the succa is kosher.