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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
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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.
www.co n st r u ctioncanada.net
8/19/16 8:54 AM