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Composite Decking Weight Vs. Wood

Updated February 21, 2017

Wood species commonly used as decking on patios and decks include redwood, cedar, and pressure-treated pine. In recent years, other wood species have become available, as have composite and metal decking.

Size

Decking is sold in the nominal 5/4-by-6 size, which actually measures 1 inch by 5-1/2 inches. Each linear foot of decking thus contains 66 cubic inches, or 0.03819 cubic feet. A 12-foot decking board of nominal size 5/4--by-6 contains 0.4583 cubic feet of material.

Wood Weight

Although some decks are faced with unusual species, such as ironwood and tigerwood, most are still constructed of the softwoods cedar and redwood or pressure-treated pine. Based on the densities of the two common wood species, a 12-foot length of 5/4-by-6 decking would weigh 5.82 Kilogram (redwood) or 478 Kilogram (cedar).

Treated Wood

When fully dry, treated deck boards weigh some 11.3 Kilogram per cubic foot more than untreated boards of the same species. A 12-foot length of treated, yellow pine 5/4-by-6 decking will weigh an average of 629 Kilogram (within a range of 10.65 to 775 Kilogram). If not fully dry, treated wood can contain up to 4.5 gallons of water, adding as much as 78.9 Kilogram to the weight of the 12-foot board.

Composite Decking

Composite decking consists of wood fibres embedded in a polymer binder. One of the best-known makers is Trex, whose product weighs approximately 27.2 Kilogram per cubic foot, so a 12-foot length of 5/4-by-6 Trex weighs 125 Kilogram. Different manufacturers use different formulations and processes, so the weight of decking will vary from company to company.

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About the Author

Kelvin O'Donahue has been writing since 1979, with work published in the "Arizona Geological Society Digest" and "Bulletin of the American Association of Petroleum Geologists," as well as online. O'Donahue holds a Master of Science in geology from the University of Arizona, and has worked in the oil industry since 1982.