Re: Bewaire of decking staining and fading . I'd like to add that most composite and PVC makers have changed their marketing to reflect low maintenance as opposed to maintenance free. Please also remember not to pressure wash plastic products, especially PE boards with wood fiber because 

It was observed that the latest produced of composite decks were more plastic-looking than wood-looking. Some consumers complain that they were not scratch-proof and mould-resistant and that they faded very quickly. With the introduction of anti-UV technology, fading in sunlight will be lessened.

Moisture that gets trapped under the decking and on top of the wood joists would tend to stay there and keep the joist from drying properly. elaborate decks of different colors and looks, many of these companies will not show you the deck several years later when it is faded from contact with the sunlight.

Within a few years, homeowners discovered that composites weathered under sunlight, got stained by cooking oil, sunscreen, or tree sap, and could grow mildew (plastic decking) and just about all major manufacturers for fading, color change, mold growth, surface deterioration, and in some cases structural decay.

Please note however UV stabilisation is of the plastic component of the product only and does not have a great affect on the fading characteristics, see above. Must be used for decks under roof/cover **; A more uniform appeal when under cover; Does not show scratches as easily; A more “timber-like” surface feel; Better 

But then try asking them to explain what makes one brand's wood-plastic composite (WPC) or polyvinyl chloride (PVC) decking or trim different from another. . you need to examine your additives–the chemicals that make trim whiter, deckboards stiffer, cores less (or more) foamy, and surfaces less likely to fade in the sun or