I recently built a deck around an oval pool. The railings, deck and trim boards where all composite materials. Composite lumber is a material that is a combination of wood and plastic. It seemed that these deck parts were made up of mostly plastic.
The longest pieces ordered for this deck where 12' long. All pieces were very dense and were considerably heavier than conventional deck materials (treated, cedar, redwood, etc.).
Even though these materials seemed to be mostly plastic, it worked like real wood. Its reaction to power tools like circular saws, miter saws, and routers was very similar to working with wood, if not better. It also chisled well, and at times seemed easier than wood.
All connections involving the composite materials was done with stainless steel screws. The deck boards (5 1/2" wide 1 1/4" thick) were screwed down to the joists with stainless steel trim screws. When the screws were buried below the deck boards surface, the material mushroomed around the head of the screw. Hitting this area back down with a hammer made the screws nearly invisible. This was also the case with the railings and trim boards.
The cost of composite decking and railings is more than conventional lumber. The fact that composite materials will not rot, fade or need to be stained or painted may far outweigh that cost factor.
Mike Merisko (C)2008