Homeowners will typically encounter seven main types of electrical boxes, and each type has its own best use case scenarios
Electrical boxes are an essential part of any home electrical system. They house wiring connections, the parts of your electrical system where wires join an outlet, switch, or even other wires. These connections are especially fragile, and if damaged, pulled apart, or loosened, you could face a power outage or dangerous electrical fire. An electrical box will protect these crucial connection points from any potential issues.
There are a dizzying array of electrical boxes on the market. But don’t worry. Most electrical boxes fall into seven main types, specializing in a load rating tailored to specific tasks and electric appliances.
Metal and Plastic Electric Boxes
The majority of electric boxes are metal or plastic. Most indoor metal boxes are steel, while indoor plastic boxes are PVC or fiberglass. Weatherproof metal boxes for outdoor use are typically durable aluminum alloy. Some situations require a metal box over a plastic box, such as using a metal conduit to run wiring. If you are using a non-metallic cable to run wiring, like a Type NM-B (non-metallic sheathed cable), you can choose a metal or plastic container.
As a note, metal electrical boxes must connect to the system ground, typically via a short length of wire called a pigtail. Plastic boxes do not usually require such grounding.
1. Standard Rectangular Boxes
When you picture an electrical box in your head, you will likely imagine a standard rectangular box. These electrical boxes protect the wires associated with single light fixture switches and standard power outlet receptacles. This type is also referred to as a single-gang or one-gang box, and they are generally 2” x 3” in size, with depths ranging from 1.5” to 3.5”. If you have a complex electrical setup, many rectangular boxes are “gangable,” meaning they feature detachable sides that allow multiple boxes to link together. How modular!
Standard rectangular boxes also come in both new-work and old-work designs. Install a new-work box after the wall has been framed but before adding drywall. Install an old-work box, otherwise known as a retrofit box, after you finish the walls.
2. 2-Gang, 3-Gang, and 4-Gang Boxes
You can join multiple standard rectangular boxes together to handle the electrical needs of numerous household switches and outlets, or you can go with 2-gang, 3-gang, or 4-gang boxes. As the names suggest, these are similar in function to rectangular boxes, but they are oversized to mount up to four devices side-by-side. Just like standard rectangular boxes, you can find these in a variety of new-work and old-work designs. Some even have built-in cable clamps for convenience.
3. Round Pan Electrical Boxes
Round pan boxes, also known as pancake boxes, tend to be shallow, at just 0.5” to 0.75” deep. They’re best for ceiling or wall-mounted lighting fixtures that weigh no more than fifty pounds. Ensure the fixture wires are properly connected and fitted. These are shallow boxes that can only fit two or three connections, and overstuffing them can lead to hot ceiling fixtures and, eventually, an electrical fire. If the setup demands more wire connections, go with a full-sized box.
4. Octagon and Round Electrical Boxes
Octagon and standard round electrical boxes provide more room than shallow round pan boxes, with depths ranging from 1.5 to 3” deep. This is the most traditional choice for ceiling or wall-mounted lighting fixtures that weigh up to 50 pounds. Many round electrical boxes have fasteners, or “ears,” that can attach to the wall or ceiling surface so you can avoid cutting a large hole in the drywall. This makes them especially suited for old-work applications.
5. 4-Inch Square Electrical Boxes
Standard square boxes, also known as 4-inch boxes, provide plenty of depth for multiple applications (1.25 to 2.125”). The square corners offer even more interior space for multiple conductors and connectors. For these reasons, square boxes are handy for running conductors in two or more directions. They attach to ceilings or walls and easily support lighting fixtures, housing switches, and related electrical receptacles.
Square electrical boxes also shine when used as a junction box, as they boast plenty of space to protect wire splices and the like.
6. Ceiling Fan Electrical Boxes
These boxes are purpose-built for, you guessed it, mounting ceiling fans. They come in various types and sizes to suit different kinds of fans, though they are usually round. If you are installing a new ceiling fan, make sure the associated electrical box is UL-listed for ceiling fan mounting and marked “for use with ceiling fans.” Do not use a standard round or octagonal electrical box for mounting a ceiling fan, as they likely will not be able to withstand the dynamic loading of a rotating fan.
7. Outdoor Electrical Box
These boxes are weatherproof and tailor-made for mounting to the surface of roof overhangs, decks, and exterior walls. If you have a complex backyard electrical setup, you likely have a number of weatherproof outdoor boxes. Plastic outdoor boxes are usually high-impact PVC, and outdoor metal boxes are typically made from durable aluminum. Outdoor boxes must have a cover that has been rated for damp or wet locations.
Covers and Box Extenders
It can help to learn a bit about box covers and box extenders. Electrical box covers enclose the front of the box, which is usually required by code. In other words, it is unsafe and typically illegal to leave an electrical box uncovered. Solid box covers are great for junction boxes or unused boxes, while those with cutouts can accommodate switches and outlets.
Box extenders, otherwise known as extension rings, come in a bunch of different shapes and sizes to match all of the aforementioned box types. They are box-shaped but have no back, as they attach to standard electrical boxes to increase the overall capacity. Box extenders can also bring a box flush with the drywall or ceiling for aesthetic and functional purposes.