Choosing material for a new deck used to be a simple proposition: There were pressure-treated lumber, which most people used, or fancier woods such as cedar, redwood and mahogany. Then came Trex, and a bunch of other composites, and the alternative decking market exploded. Cellular PVC, capped versus non-capped, decking made from recycled nylon carpet, special fasteners, not to mention all those railing systems.