Decks not only serve as the perfect spot for a family gathering, but also provide a low-cost way to add extra living space when your home is bursting at the seams. While building a deck almost always costs less per square foot than adding interior space, the cost of a deck project can be substantial when figure in materials and contracting labor. Compare the cost of different deck materials and options to determine if a new deck fits your budget. If you've got carpentry skills, you can bring those costs down by doing the work yourself.

Backyard Deck
credit: fallbrook/iStock/Getty Images
Beautiful outdoor deck with dining table

Economical Wood

Pressure-treated lumber remains one of the most economical options for deck building. Remodeling Magazine estimates the cost of an average 16-by-20 foot deck at $9,539 as of 2014. This figure includes structural supports, decking, a built-in bench, basic rails and three stairs. This breaks down to about $30 per square foot installed. If you plan to build the deck yourself, plan to spend $1.50 to $5.00 per square foot for decking and $4 to $6 per square foot for joists and other framing materials. High-end woods such as cedar, redwood and ipe -- Brazilian walnut -- can cost more than twice as much as pressure-treated lumber.

Low-Maintenance Composites

Composite decks tend to cost more up front, but require less maintenance and care over time, making them cheaper in the long run. The average 16-by-20 foot composite deck costs $15,437, which breaks down to just under $50 per square foot. A high-end composite deck with a more elaborate design and a second platform measuring 10 feet in diameter costs an average of $35,158.

Estimating Extras

Many factors increase the cost of your new deck. Decks situated more than a few feet off the ground require more structural support and a greater number of stairs, upping the cost. Fancy rail systems, complex decking patterns, high-end finishes or unusual designs and shapes can also increase the price. If you add built-in seating, plan to pay more for the materials and support system.

Decks and Home Value

Despite their high cost, decks remain a relatively good investment. Remodeling magazine indicates that an average wood deck provides an 87 percent return, while a typical composite deck provides a return of 74 percent, when you sell the home. Extravagant decks provide a slightly lower return, with upscale composite decks returning 65 percent of their cost. In some areas of the country, a deck can increase the return on your investment to 109 percent if you live in California, Washington, Oregon or Alaska when you sell the house.