Abstract: A joist end cap overcoming the shortcomings of prior joist end caps is disclosed. A joist end cap having five walls, namely a top wall, bottom wall, pair of side walls and end wall, define a cavity for receipt of an end of a piece of lumber. The bottom wall is slanted to allow moisture to exit from the cavity. The top and bottom wall may be interchangeable, such that the top and bottom wall are both slanted and users may use the end cap in either orientation. Elongated ribs and projections along inner surfaces of the walls provide for air flow and run off of any undesired moisture. A unique connector guide and circular ring configuration ensure that connectors (e.g., nails, screws or rivets) used to connect the joist end cap to the lumber do not damage the joist end cap and/or create ingresses for moisture to enter the cavity.