How to Use an Electrical Box Extender

An electrical extender box
From Amazon

The electrical code requires that all electrical boxes, including those holding outlets, switches, or light fixtures, must be installed so that the front face is flush with the wall surface. This is to ensure that the box is sealed and the wires inside properly protected. Sometimes an electrical box is improperly installed so that the front edge of the box is recessed back into the wall—a problem that occurs most often during remodeling, such as when new paneling or backsplashes are installed over an existing wall surface. Fortunately, there is an easy fix—a device known as a box extender.

Box extenders are metal or plastic rings available in varying sizes and depths to fit snugly around or just inside an existing electrical box. When installed over an existing box, they extend the box so it is flush with the front face of the wall, thereby creating a code-approved enclosure for the wire connections inside.

Tools and Supplies You Will Need Need

  • Box extender
  • Non-contact circuit tester
  • Screwdriver
  • Device mounting screws (if needed)


  1. Choose the Correct Box Extender

    Box extenders are available in several sizes and shapes to match different box sizes and different depth needs. Make sure to choose one that matches the outer dimensions of your electrical box, and one with a depth that closely matches the gap between the face of the wall and the front of the recessed electrical box. Your extender needs to cover the gap around the box fully, and it may overlap the box slightly when you insert it. It doesn't matter the material of your box, you can get a box extender in either material.

  2. Turn Off the Power

    The first step to installing the box extender is to turn off the circuit that you'll be working on. Go to your electrical panel, whether it be a circuit breaker panel or fuse panel, and look at the listing chart on the door to identify the right circuit breaker or fuse. Switch off the circuit breaker or remove the fuse controlling the device in the electrical box you're working on.

  3. Check for Power, Remove Device

    Check the outlet or switch for power using a non-contact circuit tester. Once you are sure the power is off, remove the mounting screws holding the outlet receptacle or switch to the electrical box. Gently pull the device out of the electrical box by pulling on the mounting strap. There is generally no reason to disconnect the circuit wires from the device.

  4. Attach the Box Extender

    Slip the box extender over the device and slide it into the electrical box. The fit should be tight. Usually, you can slide the extender over the switch or receptacle without disconnecting the circuit wires. If the circuit wires prove to be too short for the extended depth created by the extender, you can attach pigtail wires to the circuit wires to make the connections to the device.

  5. Reattach the Device

    The holes for the mounting screws on the extender should match up exactly with the holes on the existing box. Push the switch or receptacle back into place, so the mounting holes on the strap line up with the holes in the box, then reattach the device to the box, using the mounting screws. If the existing screws are too short, you can replace them with longer screws to accommodate the added depth created by the extender.

  6. Attach the Cover Plate and Test

    Make sure the switch or outlet is level, then reattach the device's cover plate. Turn the power back on the main service panel and test the outlet or switch to make sure it is working properly.