Abstract: A barbed light weight concrete fastener and plate comprises a fastener with a head and two bendable legs. Each leg has a barb and a bump protruding therefrom. The fastener is pushed through a base ply and into a roof deck of cementitious material. The legs diverge to capture a concrete wedge between them. The barbs dig into the concrete wedge to increase resistance to a pullout force. The bumps create pressure points with the cementitious material that further resist pullout. A plate may be interposed between the fastener and the base ply. The plate has a number of openings therethrough of relatively large area. The openings are filled with plugs of asphalt that adhere to the base ply. Pulling of the base ply is resisted by the plate acting against the shear areas between the asphalt plugs and the base ply.