The composite joist floor system includes joists supporting metal decking and a stand-off fasteners are spaced along the length of the joist Each fastener has an upper portion with a through hardness between HRB 70 and HRC 40 and a lower portion having a threaded portion with a through hardness of between HRB 70 and HRC 40 and a thread-forming portion adjacent the threaded portion with at least a HRC 50 hardness and failure torque to thread-forming torque of at least 3.0 and a drive torque at least 20% less than a thread-forming torque, and a fluted lead portion adjacent the thread-forming portion with a nominal diameter between 70 and 95% of major diameter of the threaded portion adapted to form a fastener opening. These stand-off fasteners extend into and are encapsulated by a cementitious slab supported by the metal decking to form a composite floor system.