Abstract: A decking system includes an extruded metal ledger board for mounting onto a supporting surface of a building structure and extruded metal joists which can be cut to length and joined to the ledger board using mounting clips that can be secured to the joists. A beam supporting the joists thereon and fascia trim members surrounding the perimeter of the decking system can also be used which are formed of extruded structural members arranged to be mated to the joists. A stair assembly formed of extruded structural members can also be mated together to form stairs connected to the decking system. Post supporting elements can also be coupled to the joists for supporting railing posts about a perimeter of the decking system.