Composite Decking Weight Vs. Wood

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.

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.

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 12.83 pounds (redwood) or 10.54 pounds (cedar).

When fully dry, treated deck boards weigh some 0.25 pounds 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 13.87 pounds (within a range of 10.65 to 17.08 pounds). If not fully dry, treated wood can contain up to 4.5 gallons of water, adding as much as 17.4 pounds to the weight of the 12-foot board.

Composite decking consists of wood fibers embedded in a polymer binder. One of the best-known makers is Trex, whose product weighs approximately 60 pounds per cubic foot, so a 12-foot length of 5/4-by-6 Trex weighs 27.5 pounds. Different manufacturers use different formulations and processes, so the weight of decking will vary from company to company.