Fascia screws are the fasteners used to secure fascia and riser boards to framing members. Because fascia is usually about half the thickness of the decking, a full length deck screw is not needed (but can be used in some cases).
PVC fascia can be installed without needing to pre-drill any screw holes, because the expansion/contraction with PVC is not as dynamic as with composite. The middle and left photos show examples of screws designed for PVC fascia.
Composite fascia requires a different screw (right photo) and a hole drilled and counterbored specifically for that screw. The hole is slightly bigger than the screw shaft, allowing for more movement of the fascia. The pre-drilled hole is shaped so that the wider head of the screw can sit recessed into the surface of the fascia board.
Overall, the thermal movement of composite fascia boards is more dramatic and forceful, to the point where the fascia should be allowed to move. On PVC fascia, the expansion and contraction can be held at bay, both by adequate fastening, and the fact that the lower density of PVC allows it to compress without bowing or "oil-canning".
