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Photos courtesy MoistureShield Feature Stacking the Deck Wood-plastic composites help marinas achieve durability By Brent Gwatney and Randy Pearce M arinas face some of the most demanding environmental conditions of any type of structure. High moisture, sun, salt, freeze/thaw cycles, fungal decay, and insects all work together to degrade decked surfaces. Additionally, according to the World Association for Waterborne Transport Infrastructure (PIANC), the “intermittent drying and wetting in the tidal and splash zone causes alternate swelling and shrinking of wood, which ultimately produces multiple internal fractures in timber.” 1 Although these negative impacts are most pronounced in saltwater environments, the decking employed in freshwater marinas might also face potentially damaging natural phenomenon and weather elements. To build longer-lasting decked surfaces, many marina owners across Canada are installing wood-plastic composite (WPC) products for their docks, decks, and boardwalks. A WPC is a non-structural building material that “can be produced to any shape and size, can be hollow core or solid, and can encompass curves or complex forms,” explains Natural Resources Canada (NRCan). 2 North American manufacturers produce 44 September 2016 CC_Sept_2016.indd 44 a range of WPC products, including decking, railing, window, and door components. The wood fibre in WPCs is typically composed of fine particles with a consistency similar to sand or sawdust. This wood fibre is combined with common plastic formulas including polyethylene, polypropylene, and polyvinyl chloride (PVC). The wood fibre and plastic used can be virgin materials or the products of various recycling processes. WPC decking and railing typically contain 50 to 60 per cent wood fibre. Most of the remaining volume is plastic, and this wood-plastic combination might comprise anywhere from 80 to 95 per cent of a WPC board. The remaining components of WPCs might include small amounts of additive such as pigments, stabilizers, and fungicides. 3 Physical attributes WPCs combine the best attributes of both wood and plastics—making them true hybrid materials. 4 These properties provide a number of physical characteristics enabling superior performance for decked surfaces in marinas. n st r u 8/19/16 8:54 AM