A component such as a siding panel comprised of a PVC/wood flour composite. Another embodiment is a component such as a siding panel that is made from a PVC/CPE/wood flour composite. The cellulosic composite may be extruded through a die and then bent into the shape of the component. Optionally, a reinforcement backer (e.g., an expanded polystyrene foam panel) may be adhered to the cellulosic composite siding.