The maximum span for a wooden deck joist depends on several factors including the types of wood species, grade, spacing between joists, and the total load it will bear (e.g., live load, dead load). However, as per rough estimates: a 2×8 deck joist can span up to 12 feet, a 2×10 joist can span up to 16 feet, a 2×12 joist can span up to 18 feet, 2×6 joist can span up to 9 feet and a 2×4 joist can span up to 6 feet.

Deck joists are repeated structural member that are used to construct deck frame. The minimum size of joist you would need for deck depends on span of deck, spacing between joist and building code in your area. There are several species of wood like Southern pine, Douglas fir-larch, Hem fir, Spruce pine fir, Redwood, Western cedar and etc are used as deck joist.

Deck joists are horizontal framing members that support the decking boards of a deck. They are typically made of wood or composite materials and are installed perpendicular to the beams or ledger board of the deck. The common sizes for deck joists in residential construction are typically 2×6, 2×8, 2×10, or 2×12 inches, with larger joists used for longer spans or heavier loads.

The normal spacing between deck joists is 16 inches on center. However, 12 and 24 inch spacings are also used. The larger the space between the joists, the less span there is likely to be, while the smaller the space between the joists, the more span. Therefore, when choosing the right size of deck joists for your deck, the distance between the deck joists also plays an important role.

The most common sizes of deck joists are 2×6, 2×8, 2×10 and 2×12 and that are used for deck construction with a maximum joist spacing of 16 inches. The joist material consist of different types of wood, for example southern pine or Douglas fir, larch, etc.

## Here’s are general guideline for how far can a 2×8, 2×10, 2×12 and 2×6 span for a deck:

- For deck construction, a southern pine 2×6 joist can typically support a span of up to 9 feet 0 inches at 16 inches apart, a span of 9 feet 11 inches at 12 inches apart and a span of 7 feet and 7 inches at 24-inch spacing.
- For deck construction, a southern pine 2×8 joist can typically support a span of up to 11 feet 10 inches at 16 inches apart, a span of 13 feet 1 inches at 12 inches apart and a span of 9 feet and 8 inches at 24-inch spacing.
- For deck construction, a southern pine 2×10 joist can typically support a span of up to 14 feet 0 inches at 16 inches apart, a span of 16 feet 2 inches at 12 inches apart and a span of 11 feet and 5 inches at 24-inch spacing.
- For deck construction, a southern pine 2×12 joist can typically support a span of up to 16 feet 6 inches at 16 inches apart, a span of 18 feet 2 inches at 12 inches apart and a span of 13 feet and 6 inches at 24-inch spacing.

Conclusions:

The maximum span for a 2×12 deck joist should be 18 feet, while the maximum span for a 2×10 deck joist should be 16 feet. Likewise, the maximum span for a 2×8 deck joist should be 12 feet, while the maximum span for a 2×6 deck joist should be 9 feet.