How to Install an Old Work (Retrofit) Electrical Box

Installing an old work or retrofit electrical box allows you to add a new electrical outlet into an existing wall without having to cut into the wall and patch it afterwards. This can be a handy way to add additional outlets in your home without major renovation work. With some basic DIY skills and the right materials, installing a retrofit electrical box is a manageable project for most homeowners.

What You’ll Need

Before starting this project, make sure you have the following tools and materials on hand:

  • Retrofit/old work electrical box – Specifically designed with adjustable flaps that fold out to sit flush against the inside of the wall.
  • Drywall saw – For cutting hole in wall to fit electrical box.
  • Voltmeter – To test for live wires in the wall before starting. Safety first!
  • Screwdriver – Phillips head screwdriver to secure electrical box.
  • Wire strippers – For connecting wires.
  • Electrical tape – For covering stripped wire ends.
  • Drywall anchors – For further securing electrical box to wall.
  • Electrical wires – 14/2 or 12/2 NM cable based on circuit.
  • Wire nuts – For connecting wires together.
  • Electrical outlet – Match the style of existing outlets.
  • Drywall compound – To patch over electrical box once installed.
  • Sandpaper – Help smooth patched drywall once compound dries.

Step 1: Turn Off Power

Before installing anything electrical, you must ALWAYS turn off power to the circuit you’ll be working on at the breaker box. Test with a voltmeter to ensure no live power is running through the wires behind the wall. Working with live electrical wires can result in severe shock or electrocution, so this step is critical for safety.

Step 2: Choose Installation Location

Consider where you want the outlet positioned. Most standard wall outlets are spaced 12-18 inches apart and about 12 inches up from the floor. Avoid installing directly over flooring seams or too close to countertops or cabinets which could obstruct use. Check the opposite wall to line up placement evenly. Mark the wall with a pencil where the outlet will go.

Step 3: Cut Hole In Drywall

  • Use a drywall saw to cut a hole in the wall about 2 1⁄2 inches wide and 4 inches high. This allows room to fit and secure the electrical box. The hole can be round or square.
  • Cut the opening about 1/2 inch above your final outlet location mark. This allows space below to feed in and connect the wires.
  • Cut carefully and cleanly to minimize need for extra patching later.

Step 4: Mount Electrical Box

  • Fold out the adjustable flaps on the retrofit electrical box and insert into the hole so the flaps press flush to the inside wall.
  • Position with the long side of the rectangular box oriented vertically. The open side of the box should face downward.
  • Use a screwdriver to turn the mounting screws on the adjustable flaps until the box is drawn tight and secure within the wall cutout.
  • If needed, insert drywall anchors through the electrical box holes into the wall for extra support. Do not over tighten.

Step 5: Fish Electrical Wires

  • Shut off power again at the breaker before working with any wires. Verify with a voltmeter that the wires have no live current.
  • Locate the nearest live wires in the wall, typically coming from the closest existing outlet box.
  • Turn the power back on temporarily in order to use a voltmeter or non-contact tester to identify the hot (black), neutral (white), and ground (green or bare copper) wires. Mark them with tape.
  • Turn power back off. Use fish tape from the new outlet box to pull the wires through the walls to the location of your new electrical box. Leave at least 6 to 8 inches of additional wire.
  • For NM cable with ground wire, pull all 3 wires through. For armored cable such as BX, you may only need to pull the hot and neutral if ground wire is accessible in the box location.

Step 6: Connect Electrical Wires

  • Carefully strip the ends of the new wires extending into the outlet box location by cutting away about 1/2 inch of insulation.
  • Secure the white (neutral) wire to the silver screw terminal on the outlet. The black (hot) wire connects to the brass screw terminal.
  • The ground wire should be connected to the green screw terminal on the outlet, or attached to the green grounding screw located within the electrical box.
  • Twist the copper ends together tightly using pliers and secure with a wire nut.
  • Wrap all connections with electrical tape for an extra protective layer. This helps prevent shorts.

Step 7: Install Outlet & Patch Drywall

  • With wires connected securely, tuck them neatly into the electrical box leaving room for the outlet. Secure outlet to box using long screws provided.
  • Test outlet by turning power back on at the breaker. Use a voltage tester to confirm outlets are wired correctly.
  • Mix drywall compound to plaster over any gaps between wall and electrical box. Let dry completely.
  • Use sandpaper to smooth over hardened compound for a flush wall surface. Carefully vacuum dust.
  • Prime and paint patch to match surrounding wall color. Allow paint to dry fully before using new electrical outlet.

And that’s it! By following these steps you can successfully install an old work electrical box to add a handy new outlet to your home.

Frequently Asked Questions About Installing Retrofit Electrical Boxes

Q: Is it safe for a homeowner to install an old work electrical box?

It is safe if proper precautions are taken and instructions are followed carefully. Make sure to turn off power at the breaker and double check wires are not live before working. Review full circuit breaker safety. Consider consulting an electrician if unfamiliar.

Q: How do I determine the right type of electrical box to buy?

Look for boxes specifically marked “old work” or “retrofit” with adjustable flaps. Measure the wall depth to ensure the box will fit flush within the space. Match the box style and finish to existing outlets (i.e plastic, metal).

Q: What tools do I need to install an old work electrical box?

Essential tools are drywall saw, voltmeter, screwdriver, wire strippers, electrical tape, and wire nuts. Helpful extras include fishing/fish sticks to pull wires, drywall anchors, and drywall compound for patching.

Q: Where can I get the NM cable wires to connect the outlet?

Use the existing wires from the nearest outlet as source wires. The cables need to be long enough to pull through walls to new box location. Buy similar gauge NM cable if extending length is needed.

Q: How do I ensure proper grounding when installing the outlet?

Connect the ground wire in the NM cable to the grounding screw or wire in the electrical box itself. Also attach to the ground screw on the outlet. Continuity is critical for safety.

Q: Can I install an old work box in a bathroom or near water sources?

Special considerations are required for wet locations like bathrooms. Use appropriate water-resistant boxes and GFCI outlets marked for bathroom use. Consult an electrician for bath/kitchen installations.

Q: What is the proper height to install an electrical outlet on the wall ?

Standard outlet height is 12-18 inches above the floor. Position higher over countertops or furniture as needed. Align evenly with outlets on opposite walls. Place at least 12 inches apart if installing multiple outlets.

Q: How deep into the wall should the electrical box be recessed?

When installing the retrofit box, the adjustable flaps should fit snugly against the back interior wall surface. The open face of the box should be flush with the outer wall surface once screws are tightened.

Q: Do I need a permit to install an old work electrical outlet box?

Electrical permits are not always required for basic household projects like this. But do check with your local municipal building department to learn about requirements in your area. Better safe than sorry.


Installing an old work or retrofit electrical box takes careful planning, the right tools and materials, and attention to critical safety issues like turning off the power. But with some basic electrical know-how and DIY skills, it can be an achievable project for many homeowners. Follow the steps outlined above and you’ll have stylish new outlets added anywhere you need them in your home. Just be sure to put safety first! Consult an electrician if any doubts or concerns arise regarding proper electrical wiring procedures. Taking the extra time to install boxes correctly will provide outlets that safely serve your needs for years to come.