Yosef Karo, Translation:Shulchan Aruch — Orach Chaim 638…
“ We do not benefit from them for other things for all eight days because on the seventh day the sukkah itself is entirely muktzeh until twilight, and since it is muktzeh for twilight it is muktzeh for the whole [eighth] day. Rem"a: Even if the sukkah fell over, it is forbidden, and a condition [that it will be permitted if it falls] is not effective (Tur) . But wood that leans on the sukkah is permitted [to be used] , see 518:8. And if after the minimum requirement for the size of the walls is met and the valid sukkah is complete, one adds a wall, it is not forbidden. ”
