Electrical boxes enclose wire connections for
applications such as a light switch, electrical outlet or light fixture. Specific
boxes are designed for use indoors, outdoors, for attaching to the outside of
walls, for behind walls and other applications.
In addition to enclosing wiring connections, electrical boxes:
Provide convenient access to electrical components for regular maintenance and upgrades and
Offer protection that grounds electrically charged wires and prevents short circuits that could lead to fire.
The National Electrical Code and local building codes regulate the types of
electrical boxes that can be used in specific applications, as well as the
manner of installation. In addition, code requires that electrical boxes not
be covered with drywall, paneling or other wall covering, but with electrical
box covers that can be matched to all boxes.
Check with your local building inspector before you start any electrical project and be sure to obtain required permits. When your work is complete, always have it inspected for compliance with local codes to ensure that it has been safely installed.
This buying guide describes the different types of electrical boxes, their materials and applications so you can feel confident you’re choosing the right box for your project.
Factors to Consider
Handy box – A handy box mounts on the surface of a wall and can contain light switches or receptacles. Handy boxes are ideal for areas where behind-the-wall installation is not possible or is difficult.
Junction box – In a junction box, wires connect only to each other, never to a switch, receptacle or fixture. This type of electrical box allows circuits to be safely split and branched into different directions.
New-work box – Electrical boxes installed as part of a new construction project are called new-work boxes. New-work boxes are mounted directly to studs or joists, or placed between two studs using a bar hanger before drywall is applied.
Old-work box – Remodeling boxes, also called old-work boxes, are electrical boxes designed to be installed after drywall has been hung. For example, if you need an additional outlet for a home office or theater. Old-work boxes hang on the drywall with clamps built in to the box. Our How to Install a Remodeling Box Project Guide walks you step-by-step through the installation of a remodeling box.
Outdoor box – Available in metal and nonmetallic units, outdoor boxes protect wiring from the elements with gaskets, sealed seams, and in some cases watertight covers.
Standard rectangular box – These most common boxes house a single electrical switch or outlet.
Square box – Also called double-gang box, these boxes house two devices, either a combination outlet/switch or a pair of outlets or switches in one location.
Round or octagonal box – Houses lightweight fixtures or safety devices in the ceiling such as a light or smoke and carbon monoxide alarms.
Ceiling box – Used for heavier fixtures, such as ceiling fans or chandeliers. Be sure to choose one that is specifically designated to support the extra weight.
Electrical boxes are constructed of either metallic material, such as aluminum, steel or cast iron, or nonmetallic material, such as PVC or plastic. Each material provides the necessary protection to keep your home's electrical system working safely under specified conditions.
Metal boxes have characteristics that differentiate them from plastic or PVC. Many local building codes require metal junction boxes because they are durable and ensure long lasting performance. In addition, metal boxes should be used for exposed indoor applications, such as with conduit in an unfinished basement.
Plastic or PVC boxes are an inexpensive and easy-to-install solution for both new-work and old-work situations where they can be placed behind drywall. Plastic boxes should only be used with nonmetallic cable.
Box covers: Once a box has been installed and devices have been
attached to the wiring inside, code requires an appropriate cover.
Braces and bar hangers are mounted between joists to allow lights or
other devices to be positioned in a variety of locations. For example, when
installing a ceiling fan in a finished ceiling, inserting a brace through a
hole cut in the ceiling between joists allows for easy positioning and minimal
ceiling repair work. Some bar hangers come with an electrical box attached.
Extension rings allow you to increase the depth of your electrical box,
providing more space to accommodate a larger number of wires.
Adjustable depth boxes can be adjusted to allow installation of the box
flush with the surface of a wall, no matter the depth of the wall material.