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How to Install a Double Gang Box


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In this article, you will learn how to install a double gang electrical box, also known as a two gang electrical box.

We install double gangs the same way we install a single gang electrical box, except we add two screws to the front of a two gang box (making sure these front screws are flush to allow for a good drywall installation).

This article is from my electrical rough-in series!

How to Install a Double-Gang Electrical Box
Also called a Two-Gang box

What We Cover in this Article:

  • What is a Double Gang Box?
  • How to Install a Double Gang Box
  • Examples of Good and Bad Installs of a Double Gang Box
  • Why a Double Gang Plastic Box is My Favorite Box!

What is a Double Gang Box?

A double gang electrical box compared to a single gang electrical box.
It’s called double-gang because you can have two devices installed!
(This could be 2 plugs, or 1 switch and 1 plug, or 2 switches, for example!)

A double gang electrical box can be plastic, or metal. (See different residential electrical box types).

In a wood frame setting it’s best to use plastic boxes, as connectors are not needed to insert wires into the box, which saves a lot of money on big jobs!

Plastic boxes are also more affordable than metal boxes, and they aren’t as sharp when it comes to your hands 🙂

A close picture of a two-gang plastic electrical box
Notice the top screws have metal plates over the screws which continue the bonding from the back green bonding screws!
This ensures electrical devices get bonded!

A two gang box has two spaces for electrical devices. You can install 1 plug and 1 switch, or 2 switches, or 2 plugs!

If you need lots of power, you can run two homerun circuits from the same panel! Make sure you don’t splice the wires together from different circuits (unless sharing a neutral).

If you need to run a phone or cable line, that will have to be in a separate box, as you cannot mix low voltage (120V) and extra-low-voltage (ethernet, tv, phone, etc) in the same box!

How to Install a Double Gang Box

Installing a two-gang electrical box is really easy, and provides one of the strongest holds out of all electrical boxes (if installed properly!)

After finding above finished floor (A.F.F.), and measuring top of box, the first screw I like to install is the one closest on the top ear tab:

What screw hole to use when installing a double gang electrical box
Showing my preferred screw hole on box ears
Using the closest screw hole on electrical boxes will always give the tightest install.
Workflow tip: For the top, use the closest screw (easy to see), but for the bottom, use whatever hole is easy to see (otherwise you have to bend way over, or get on your knees.. the front screws on a double-gang box hold it firmly).

We put 4 screws into a double gang box:

  • 1 screw in each box ear (1 top and 1 bottom)
  • 2 screws in the front of the box.

On single gang boxes, use the closest screw hole for a strong install (especially with plugs), however, double-gang boxes don’t matter because its two front screws hold it firmly!

Step-By-Step Process to Install Two-Gang Electrical Box:

Step #1: Start by using the closest screw hole of the box’s top ear tab.

Step #2: Put a screw in the bottom ear tab (whatever one is easiest to see so you don’t have to bend over so far.. if you’re boxing all day, this protects your body!)

Step #3: Push the box tight against the stud, then install the 2 front screws flush!

My finger is pointing to the front screw holes on a double-gang box
Before screwing in the front screws, make sure the box is tight against the stud!

Examples of Good and Bad Installs of a Double Gang Box

Here’s some good and bad installation examples of two-gang electrical boxes.

The main takeaway is making sure the front screws are flush. If they aren’t, drywall can break, or worse, not allow cover plates to go on flush in finishing.

A GOOD INSTALL regarding flush front screws on a double-gang box.
The trick is making sure you put screws in STRAIGHT!
A BAD SCREW INSTALL (not flush)..
Drywall will not be able to go on well for the best install!
Good and Bad install in one picture.
Top screw is a GOOD flush install
Bottom screw is BAD (screw is on angle)
For completeness, a final image showing a GOOD two-gang box install

Take pride in your work, and make sure the front screws are screwed in properly.

It helps all trades that have to work in this area.. which includes drywallers, tapers, painters, and YOU AS THE ELECTRICIAN.

Why a Double Gang Plastic Box is My Favorite Box!

I really like how plastic boxes don’t cut your fingers and knuckles like metal boxes do when cutting-in wires, splicing, and tucking wires in the box.

Also, a double-gang box has lots of space, allowing you to neatly organize your wires without having to be perfect like a single gang box.

Conclusion: Recap and Reminders of Double-Gang Box Installation

A couple things to mention before closing out..

Double-gang boxes do not need to be be supported on 2 sides like a three-gang electrical box.

Comparing a single gang, double-gang, and triple gang box.
A triple gang (or more) needs support on both sides of the box.
This is so when drywall goes on, it sandwiches it for a tight install.

The next thing to talk about is SCREW HOLE HEIGHT.

If you install boxes close to each other, you NEED to make sure box heights are within a 1/16″.. otherwise it will be very noticable, especially if groutlines are present with kitchen backsplash!

You can learn more with before mounting boxes, and installing a single gang box.

Don’t miss my ROUGHING-IN SERIES for how to rough-in as an electrician!

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