When it comes to the anatomy of a deck, joists are part of a deck’s framing system. Each joist is one of a series of long, horizontal structures that support the decking itself. While posts are vertical, joists lay horizontally on top of each beam to provide a sturdy, level surface to lay your decking materials across.

Joists are the repeated structural members that are used to build a deck frame. The minimum size joist used in deck construction depends on the distance the joists span between bearing points and the species and grade of the treated lumber used to create the joists.

Joists are structural elements that make up the framework of the deck beneath the deck’s walking surface. Joists attach to a ledger board using joist hangers and run the entire length of the deck, perpendicular to the house. Deck joists, like the rest of your deck’s frame, can be made from a few different materials.

Joists (or studs) have flanges whose edges turn inward, whereas track’s flanges are straight. Track is sized so that the joists fit between its flanges. In deck building, two steel shapes are used: joists (or studs) and track (see illustration).