S.C. Code Regs. 8-1211. IRC Section R312.1.1 Where required

Guards shall be located along open-sided walking surfaces of all decks, porches, balconies, floors, stairs, ramps and landings that are located more than 30 inches measured vertically to the floor or grade below and at any point where a downward slope exceeds 3V:12H within 36 inches (914 mm) horizontally to the edge of the open side. Insect screening shall not be considered as a guard.