The size of the deck also has structural implications. Your architect, engineer or contractor should size the beams, joists and pier footings so that the deck not only meets structural requirements but also feels stable to the people on it. The higher people are off the ground, the less comfortable they will be with the deck moving underfoot. Also, keep in mind that in addition to increasing the cost of decking materials and labor, adding square footage will increase the number of concrete footings to dig and pour. Oversizing the deck by two feet in one direction may mean an additional row of footings. Discuss the structural implications with your designer so you can get the deck that is the right size for your family at the price that's easiest on your pocketbook.