Abstract: The present disclosure relates to a penetrating fastener for a roofing system having a flexible waterproof membrane adhesively attached to an upper layer which is fastened to a roof deck. The fastener is dimensioned to extend through the upper layer and threadingly engage the lower roof deck. The fastener includes a self-drilling tip for piercing the upper layer and the roof deck and a self-tapping threaded shank portion located above the tip. An unthreaded shank portion is located adjacent the threaded shank portion. A tapered collar is located above the unthreaded shank portion. The fastener further includes a driving head which has a flange extending at an angle from a first side of the head to the tapered collar for reducing the tensile forces associated with the head being installed flush with or slightly below the upper layer.