Electrical Boxes: Junction Box, Outlet Box, Single Gang, 2 Gang

Electrical Boxes vary in size, material, number of gangs, and shape and are designed for specific uses like junctions, outlets, and switch or fixture boxes for wiring in wall or ceiling. Use this guide to determine the best electrical box choice for your application.

electrical box switch box outlet box

What is a Gang Box? (single gang, 2 gang box, etc.)

A gang box is an electrical box used to enclose, or “gang up”, electrical wiring devices to help prevent short circuits. Most building codes will require this protective measure as contact between wires may cause a spark, which could result in a fire.

Electrical Box or Gang Box Sizes & Dimensions

Gang boxes come in a variety of sizes, depending upon the number of wiring devices (outlets, switches, or other electrical devices) to be added. A single gang box, or 1 gang box, is wide enough to enclose only one outlet or switch. Single gang electrical box dimensions vary by manufacturer and type, but are about 2″ wide by 4″ high. Similarly, a double gang box, or 2 gang box, is sized to enclose two wiring devices. Double gang electrical box dimensions are about 3″- 4″ wide by 3.25″ - 3.75″ high.

Other common electrical box sizes are 3 gang, 4 gang and 5 gang (this continues until 10). Size your electrical box to allow enough space for the conductors in the box by following the National Electric Code (NEC®) 314.16 for box fill calculations.

Types of Electrical Box Material: Metal & Non-metallic

Steel Metal Electrical Box

Steel metal electrical boxes are used when metal-sheathed cables or metal conduits are running in/out of the electrical box.
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Cast Aluminum Weatherproof Electrical Box

Weatherproof electrical boxes prevent moisture from penetrating the electrical box and short-circuiting the connections.
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PVC or Fiberglass Electrical Box

PVC electrical boxes should be used when there are non-metallic (NM) cables leading in/out of the box.
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Types of Electrical Boxes: Outlet, Junction, Switch, Fan, Single & Multi Gang

Each type of electrical box is designed for a specific use. Below are the most common electrical boxes, like the outlet box, junction box, light switch box, and fan box, as well as different gang boxes, from single gang and 2 gang, up to 3 gang, 4 gang, and beyond. Some electrical boxes are designed to be wall boxes, ceiling boxes, floor boxes, and masonry boxes for installation within brick walls and structures.

Outlet Box (Utility Box)

An electrical outlet box (or utility box) is designed to enclose electrical outlets, which delivers power directly to objects.
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Switch Box

A switch box is a metal enclosure that houses the parts of an electrical switch.
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Single Gang Box (1 Gang Box)

A single gang box (1 gang electrical box) is only wide enough for one switch or outlet.
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2 Gang Box (Double Gang Box)

A 2 gang box (double gang electrical box or two gang electrical box) is designed to house two devices. Combination type boxes combine outlet/switch box options or allow a pair of outlets/switches per box. Double gang electrical box dimensions are about 3″- 4″ wide by 3.25″ - 3.75″ high.
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3 Gang Box (Three Gang Box)

A 3 gang box (three gang box) is designed to house up to three devices. Three gang electrical box dimensions are about 4.63″ high by 6.5″ wide.
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4 Gang Box (Four Gang Box)

A 4 gang box (four gang box) is designed to house up to four devices. Four gang box dimensions are about 3.75″ high by 7.5″ wide.
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Ceiling Box (Round Pan or Octagon Box)

A ceiling box (round pan or octagon box) is designed for ceiling-mounted lights, fixtures, and other electrical devices such as smoke alarms, detectors, and safety and emergency lighting.
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Electrical Fan Box (Ceiling Fan Box)

An electrical fan box is designed to mount ceiling fans.
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Masonry Box (Brick Wall Box)

A masonry box is used in the installation of electrical fittings in stone or brick walls. These can support multiple gangs ranging from 1-6.
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Junction Box

A junction box is an electrical enclosure that houses one or more wiring connections. This protects the connections from environmental conditions and accidental contact.
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Electrical Box Covers and Wall Plates

Keep your electrical wall boxes, including outlets, junctions, and light switches, covered and safely hidden from sight. Multiple colors and styles of box covers, switch plates, and outlet covers are available.

Box Cover

A box cover is a protective layer over the electrical box to prevent access to the wires, and to prevent reduce the risk of fire. Boxes may not be simply covered with sheetrock. According to the NEC® 314.25, boxes need to have a cover, faceplate, lampholder, or luminaire canopy.

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Outlet Plate Covers

An outlet plate cover or receptacle cover is designed to prevent contact with live electrical parts housed inside the outlet (receptacle) box.
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Switch Plate Covers

A switch plate cover conceals and protects an electrical switch that is mounted in a typical gang box.
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Weatherproof Box Covers

Weatherproof box covers can be used in outdoor locations that see humidity and water. For installation of boxes in damp or wet locations, see NEC® 314.15
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Mud Ring

A mud ring helps installers work quickly with free hands by holding an electrical box in place.
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Electrical Box Extender

An electrical box extender adds depth to a wall, aiding in electrical boxes sitting flush with a surface to prevent any sparks.
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Telescoping Bracket

A telescoping bracket allows for easy installation of electrical boxes between wall studs.
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Planning Electrical Outlet Box, Light Switch Box, or Ceiling Box Installation

When installing new electrical outlet, junction, fixture, or switch boxes in a room, remember these helpful tips:

  • Always remember to disconnect power to the area you are working on before beginning any electrical work.
  • Plan where larger pieces of furniture will be placed so the electrical boxes for outlets, switches, or fixtures will not be covered.
  • Identify where large electrical power requirements (appliances, electronics, etc.) will be placed so electrical outlets can be planned accordingly with the right 2 gang, 3 gang, or larger gang boxes to accommodate the right number and type of outlets, etc.
  • Allow for at least one electrical box per wall, if not more.
  • Use a stud finder to find the stud nearest your desired electrical box location. The electrical box will be mounted on the side of the stud.
  • Electrical outlets are typically installed 12 inches from the floor to the bottom of the outlet box.
  • The standard height for light switch box installation is 48 inches from the floor to the bottom of the switch box.
  • Plan one ceiling box for each light fixture.
  • Plan one fan box to mount each ceiling fan, centrally located as needed.
  • Plan for electrical boxes near cable outlets, and keep junction boxes at an acessible or expandable location.
  • Identify your needs for light switches, fixtures, cable, telephone, and other auxilary jacks in combination with electrical outlets (e.g., fiber optic, ethernet, satellite television systems, etc.).
  • See NEC® (National Electric Code®) 314 for requirements for electrical box installation, box fill limitations and box grounding.
  • Obtain any required permits from the building inspector for your area.

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Warning: When using this information to perform electrical work, call a licensed electrician or consult the NEC® for safety. All licensed electricians have passed examinations covering the National Electric Code®, know state and local building codes, and may carry insurance to cover damages.