How to: Deck Spacing

Install treated southern pine beams no more than 6 feet apart if the beams are a minimum thickness of 4-inches-by-6-inches. Pine beams that are a minimum thickness of 4-inches-by-8 inches can be spaced up to 11 feet apart. To space beams 12 feet apart, use pine beams that are a minimum of 4-inches-by-10 inches thick. It is acceptable to use two, 2-inch-thick boards for the 4-inch thickness.

Set beams that are a minimum thickness of 4-inches-by-8 inches no more than 7 feet apart if you are using redwood lumber. Redwood beams can be spaced up to 12 feet apart if they are a minimum thickness of 4-by-10 inches. If necessary, double the 2-inch thick boards for the 4-inch thickness.

Measure carefully to space the joists once the beams have been set. If the beams are no more than 8 feet apart, 2-inch-by-6-inch treated southern pine joists can be used and spaced either 16 inches or 24 inches on center. For beams that have been spaced eight feet to 12 feet apart, use 2-inch-by-8-inch pine joists. These joists can also be spaced either 16 inches or 24 inches on center. Although 24-inch on center joists are acceptable, in general, 16-inch on center provides more support for larger beam spans.

Position 2-inch-by-8-inch redwood joists 16 inches or 24 inches on center if redwood beams have been installed no more than 10 feet apart. If the beams are spaced between 10 feet to 12 feet apart, use 2-inch-by-10-inch redwood joists and space them 16 inches or 24 inches on center. As with southern pine, redwood joists that are spaced 16-inch on center provide better support.

Space the top surface deck boards 1/8-inch apart if the wood is dry. If the wood is still wet, butt the boards together and as they dry, a space will develop to allow for drainage.