What is Joist?

A joist is a horizontal structural member used to support a building or open spaces like floors, ceilings, or roofs.

Definition

A joist during the construction process is installed to support, but in series. Each joist is spaced out, and evenly spread across the entire structure. When joists come together, they create support for floorings, ceiling boards, decks, and other building components.

A floor joist is a type of joist used to support the floor system in a building. It helps carry the weight of people, furniture, equipment, and finished flooring.

Joist hangers are metal connectors used to secure a joist to a beam, ledger, or other support. In many wood-framed projects, joist hangers help keep the connection stronger and more stable.

Purpose

Universal purpose of a joist is to provide support and spread the load it holds in a safe way across the structure it is holding.

In construction projets, a floor joist helps create a supportive base for floors, where joist hangers also help connect joists properly to the surrounding frame. In a joist the size, pacing, and material of each can affect the entire strength of the project.

Examples of Use

Carpenters install floor joists to support flooring areas like subfloor in a new home.
A crew can use joist hangers to attach wooden beams to joists.
Estimators measure the number and length of joists that are needed for a floor framing takeoff or flooring takeoff.

Related Terms

Shelf

A flat, elevated surface where things are placed for storage, organization or display. Used in homes, offices, stores, and warehouses to maintain clutter-free spaces.

Lattice

A lattice is an open mesh structure of criss-crossed strips or slats. It is used in building construction and gardening as screening, supports, vents, and decorations.

Stucco

Stucco is a durable wall finish made from cement, sand, lime, and water, commonly used on exterior walls to create a textured and weather-resistant surface.

Notes

A joist can be made from wood, steel, or engineered lumber.
A floor joist is designed to support floor loads and transfer them to beams or walls.
Joist hangers are commonly used in deck, floor, and roof framing.
The spacing between joists affects how much load the structure can support.
Correct joist sizing and installation are important for safety, durability, and accurate construction estimating.