A decking system comprises a ledger board for mounting on an upright supporting surface, a beam, a plurality of joists for spanning between the ledger board and the beam, and a plurality of deck boards for spanning across the joists in which all of the components can be mounted to one another by interlocking engagement of various connectors so that no additional fasteners are required for assembly. The components are formed of extruded and molded materials which do not require any maintenance. A railing system and a stair system are also provided which similarly connect by interlocking engagement of the components.
