How to Run Electrical Wiring in a Home Addition


When you plan a home addition, consider how many different rooms you will be constructing and the type of electrical installations will be necessary in each of these rooms. Install an over-sized panel if your main panel will support it. This will provide plenty of electrical capacity; establish a backbone to your new electrical grid, and support additional add-on construction in the future.

Things You'll Need

  • Electrical tester
  • Screwdrivers
  • Cordless drill
  • Drill screw bits
  • 100 amp sub-panel box
  • Drywall screw
  • Stud finder
  • 1 inch conduit
  • 1 inch conduit connectors
  • Hammer
  • 1 inch conduit straps
  • Drill with hole saw bit
  • ROMEX® staples
  • Blue plastic outlet or switch boxes
  • Turn off the main power to your panel box. Use a electrical tester to ensure it's off. Use a screwdriver or cordless drill gun to remove the panel box cover.

  • Install a sub-panel below your main panel box. Consult all codes or your electrical contractor for code requirements. Attach the sub-panel directly to your studs or screw drywall screws through the back of the sub-panel box into the studs behind it. Use a stud finder if needed.

  • Punch out two, 1-inch holes, one in the main panel and one in the sub-panel. Use a hole punch to do this. Run a piece of 1-inch conduit between your main and sub-panel. Use 1-inch conduit at each connection point and tighten down with a hammer and screwdriver.

  • Install outlet boxes 12 inches off the ground. Switch boxes are usually installed about 48 inches off the ground. Check with code requirements or your local inspector for more information. Hammer the boxes to the studs, using the built in nail flanges and the hammer.

  • Run two or three branch lines from your sub-panel into the area of your remodel. Drill holes in the ceiling joists of your garage, which is a typical location for the main electrical panel. Drill holes in the studs of your addition, room by room. Outlets are usually installed about 12 inches off the ground; drill horizontal runs at this level all around the room: stud to stud.

  • Drop one branch line down from the ceiling in one of your addition's rooms. This will be used for all of your switches. Run another branch line to an outlet. This will be used for all of your outlets throughout the remodel. Your third branch line may be saved for future add-on work, or may be used for GFCI circuits if your addition will contain a bathroom.

  • Attach ROMEX® wire staples at each box connection and about every 3 to 4 feet apart. Run your ROMEX® wire to connect all of your outlets. Do the same for any switches. Remember, the outlets and switches have their own, separate feed line from the main panel. Feed the ROMEX® wire into each box and leave about 12 inches hanging out.

    Your addition is now wired. You will install the outlets, switches, GFCI outlets and light fixtures later, after the walls are closed up and inspected.

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  • Photo Credit Andy Sotiriou/Photodisc/Getty Images
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