What is capped composite decking? Capped is also called “co-extrusion” Or “cover” Deck. It is important distinction to note because that earlier generations of composite decking were uncapped, the big difference is that capped composite decking has a “cover”. That provides added protection against the elements and everyday living. As a result, they were far more vulnerable to staining and fading. Windi capped decking, the core is the traditional wood plastic composite materials (along with our g series and h series traditional decking), while the extruded surface is made of multi engineer plastic with an outer shell of plastic that completely encapsulates the board in an impermeable layer of protection from scratches, stain and fading. The extrusion process creates the decking with highly durable, long lasting and resistant to staining, fading and relative impact.