What To Know About Electrical Box Extenders

When your house or apartment was being built, electricians like me installed the boxes that hold receptacles and light switches in your walls. They nailed or screwed electrical boxes right to the studs, so the boxes (and the electrical devices they now hold) can’t move once the wall is finished.

But what if you get sick of your kitchen, and decide to install a tile backsplash over the existing wall? The boxes aren’t going anywhere, so the extra layer makes the box sit deeper in the wall than it’s supposed to — and that’s not good.

Why? Safety. Below, I’ll explain why (and how) to fix this problem with an electrical box extender.

Introduction to Electrical Box Extenders

So what’s the big deal about a box that’s a little deep in the wall? If there’s a problem like arcing or sparking inside the box, exposed combustible building materials could ignite. Electrical box extenders are sturdy rings that attach to an existing electrical box, covering the newly installed wall material so it’s protected.

Once installed, the extender brings the box edge flush with the finished surface. Non-combustible wall materials like tile and drywall are only allowed to be set back 1/4 inch or less from the finished surface. If your wall covering is plywood or another combustible material, the box edge must be flush. An extender can be used in either scenario.

Electrical Box Extender Material Types

Residential box extenders are usually made of some form of nonmetallic material, like PVC plastic. The most common colors are blue, gray and white, depending on the brand. Metal box extenders also exist, but if the box in your wall is plastic, which is likely in residential wiring, use a plastic (PVC) extender.

Box extenders come in “single-gang,” which means the box holds one device only, as well as two-gang and multiple-gang. Some extenders are “gangable,” meaning you can connect them together, but that’s more likely to be found on metal extenders.

Box extenders must be certified and marked by a Nationally Recognized Testing Laboratory (NRTL) such as Underwriters Laboratory (UL), ETL, MET, CSA, TUV or similar. The certification marks are allowed to be on the package or carton for small electrical products.

When to Use Electrical Box Extenders

The most common reason to use a box extender is if you need to add a layer of finishing material to the wall, such as tile, wainscoting, shiplap, knotty pine, pallet boards or other popular decorative wall finishes. They can also correct a device that isn’t secure in the box. This can happen if the gap around the electrical box is too big, giving the device’s mounting straps very little wall to grab. The gap around the box’s perimeter should be 1/8 inch or less— if yours is bigger, fill the gap with drywall joint compound.

Tools and Materials Needed for Installation

Installing box extenders is a doable DIY task. Here are the necessary tools and materials required.

• Non-contact voltage tester
• Standard (flat) screwdriver
• Phillips screwdriver
• Electrical box extender with two 6-32 screws

Short Overview of the Installation Process

First, turn off the power at the circuit breaker in the electrical panel. Then, use a non-contact voltage tester (as detailed in the next section) to ensure all circuits in the box are off. Then, you’ll remove the faceplate and the screws holding the device to the box, and gently pull the device out by the mounting straps.

There’s no need to dismantle the electrical connections. Slip the device through the extender. Push the extender into the existing box so that it rests on the wall, then push the device back into place. Use the screws that came with the extender to reattach the device to the box. Add the faceplate and turn on the power.

Safety Precautions

It only takes a tiny amount of electrical current to seriously injure or even kill a person, so it’s extremely important to follow safety precautions when working with electricity. Call a licensed electrician if you’d prefer that an expert take over at any time.

• Test the voltage tester. Ensure the non-contact voltage tester works by holding it to a known live circuit, like a plugged-in appliance or lamp cord. It should light up and beep. After finding and turning off your circuit at the electrical panel, test the tester again to make sure it didn’t fail while you were using it.
• Test for power at each step. You may have more than one circuit in the box, which can only be accessed once you carefully pull out the device. Turn off all circuits in the box for safety.
• Handle devices carefully. Pull out electrical devices by the mounting straps, not the wires or screw terminals. Use your hands, never pry with a tool.
• Look for signs of equipment malfunction, like scorch marks or a strange smell. Call an electrician.

Compliance with Building Codes and Regulations

When performing any electrical work, it’s important to follow your state and local electrical and building codes. Most state governments require conformance to the National Electrical Code (NEC), but different states enforce different versions of the code. For example, Texas and Minnesota have adopted the 2023 NEC rules, while New York and Pennsylvania currently use the 2020 code. Other states enforce these or previous versions.

In addition, some states and municipalities may amend or change the NEC and have their own electrical codes. Chicago is a good example of a place where they have local electrical rules. You’ve also got local building codes, which are separate from electrical codes but can overlap.

Contact your local electrical inspector to learn what’s required.

FAQs

Can I put a junction box anywhere?

No. Always consult your state and local codes, as well as the NEC, for specific requirements.

Is it illegal to bury a junction box in a wall?

You should not never bury or conceal a junction box in a wall. All electrical boxes must be accessible for maintenance and inspection. Your state and local governments set civil and/or criminal penalties for ignoring codes and safety requirements.

Sources

National Fire Protection Association: “NEC Enforcement”