Composite and PVC Decking Material
The base ingredient for both wood-plastic composite (WPC) and PVC decking is plastic. PVC decking is made from virgin PVC, or polyvinyl chloride -- a byproduct of the oil refining process and natural gas. Wood-plastic composite uses polyethylene plastic, which comes from recycled plastic products. Additives to aid the manufacturing process and improve suitability for construction are important for the quality of both types of decking and often are the most expensive parts of manufacturing.
A significant component in composite decking material is ground-up wood, referred to as wood flour. Various sources provide raw material for wood flour, including flooring factories, furniture makers and cabinet shops. Differences between wood species and harvesting practices make producing consistent quality in composite decking a challenge. Wood flour also tends to create mold issues for the decking. Many composite decking manufacturers now encase the product in capstock, a plastic substance that protects the inner core of wood fibers.
Composite decking is typically imprinted with a faux wood-grain finish and a range of colors with pleasing intensity. PVC decking retains its plastic appearance in a limited palette of neutral colors. The planks are often embossed with treads for texture, providing traction and improving the appearance. Composite decking fades over time to varying degrees depending on the manufacturer, but generally within three years the color is quite different. PVC decking retains its color, often warrantied for the lifetime of the owner.
Neither composite nor PVC decking is strong structurally, and both tend to sag without substantial support. The surface of composite decking is easily gouged, and the boards warp and splinter. PVC doesn't warp or splinter, but it's subject to damage from rocks, hail or objects thrown from a lawn mower. Composite decking needs to be sealed regularly once its coating fades, while PVC requires only periodic washing. Both types of decking retain heat to the point of being uncomfortable in hot, sunny weather.