Running Electrical Wire Behind Walls

 
Running Electrical Wire Behind Walls

Running electrical wires behind your walls is a great way to add an additional outlet or switch right where you need it. While the idea of working behind drywall or paneling can seem intimidating, fishing electrical wires behind walls is a job you can do yourself with a few common tools, a helpful assistant and a little patience. 

  

Before beginning your project, you’ll need to decide whether to pull power for your new outlet or switch from an existing outlet or directly from your breaker panel. Either way, be sure adding a new device won’t overload the circuit. For more information on calculating circuit loads, see our Installing a New Circuit Project Guide.

 

You’ll also want to diagram your wiring path. Often the simplest approach is to run cables to either the attic directly above the new outlet or switch, or to a basement or crawl space below. Running wires up to the attic or down to the basement may seem like the long way around if you’re adding a device along the same wall as the outlet you’ll use for power. However, the cost for the additional cable is more than offset by the time it would take to make the drywall repairs that result from cutting holes at each wall stud between the old outlet and the new device.  Low voltage aka datacom, cables need proper space and clearance to allow as little interference from the signal.

 

This project guide will walk you step-by-step through running basic nonmetallic (NM) electrical wires behind the walls. Before beginning any project, read and observe any manufacturer’s instructions and adhere to all recommended safety precautions carefully. If you have any doubts, consult a licensed electrician.

 

If you aren’t able to install electrical wires behind walls due to ductwork or plumbing, an alternative solution is to conceal wires using raceway, which runs along the surface of walls and can be painted to blend with your decor.

 

Preparation 

 

• Determine the location for your new device. Then decide whether to power your new device from an existing 
  outlet or from the breaker panel.
• Diagram your wiring path and measure for the length of NM-B cable you'll need. Buy some extra cable in case 
  you encounter any unexpected obstructions.
• Check with local building inspectors before doing any electrical work to ensure compliance with local codes.

 

Safety

 

• If you aren't comfortable with wiring projects, hire a professional electrician to run your new wire or cable.
• Turn off the electricity at the breaker panel to the outlet or circuit breaker you will draw power from for your 
  new device. Use a voltage tester to confirm the power is off at the outlet or breaker.
• Make sure a new device will not overload the circuit from which you draw power. 

 

Savings

 

• You can save money by doing this job yourself.
• Save time by reviewing the tools and materials you'll need for your project. Pick up everything you need in 
  one trip to the store before beginning your project.


WHAT YOU NEED FOR THIS JOB:

TOOLS:


Step 1:Turn off the Electricity

Turn off the Electricity

1.  Turn off the power at the breaker panel to the outlet from which 
      you will draw power.  


2.  Use a voltage tester to ensure power is off at the outlet.  

  

Step 2: Mark for the Electrical Box

Mark for the Electrical Box

1.  Use a stud finder to ensure the location for your new device isn’t adjacent to a 
     stud. 

 
2.  Hold the electrical box up to the wall in the location where it will be installed.    

 
3.  Trace around the box with a pencil to mark the area to be cut. Use a level to      
     ensure the outline is straight.  

  

Step 3: Drill a Hole in the Ceiling or Floor

Drill a Hole in the Ceiling or Floor

1.  If you’ll be running cable through the ceiling, carefully drill a hole with the 1/8 in.
     drill bit through the ceiling above the new wall box location. If you’ll be running    
     cable through your basement or crawl space, drill into the baseboard or floor right
     next to the baseboard instead.
 
2.  Insert a stiff wire or straightened coat hanger into the hole.

 
3.  In your attic or basement, look for a two-by-four beam adjacent to the protruding      stiff wire. In an attic, this beam is the top of the wall, known as the top plate. In a      basement, it’s the bottom of the wall, known as the bottom plate.

  
4.  If the two-by-four is under a piece of plywood, or covered in some other way,    
     measure 2-1/2 in. from the reference wire toward the two-by-four and drill there.  
    That should put the hole in the middle of the plate.

  
5.  Check with a flashlight to be sure there are no electrical wires or plumbing pipes 
     behind the walls where you will be working.

  

Step 4: Cut the Opening for the Electrical Box

Cut the Opening for the Electrical Box

1.  Drill a 1/2 in. starter hole at a corner of your electrical box outline.

  
2.  Starting at the hole, cut along the outline with the drywall saw. It’s okay if the     
     edges of the opening are rough. You can conceal the opening with a wall 
     plate.  

  

Step 5: Run the Cable

Run the Cable

1.  In your attic, use the spade bit to drill a hole through the top plate, directly above
     the new electrical box location. If you’re running cable through a basement or     
     crawlspace, drill a hole in the bottom plate directly below the box.


2.  Feed your fish tape into the wall opening, pushing it up into the hole you made in
     the top plate. If you’re running cable through a basement or crawl space, push it 
     down to the hole in the bottom plate. You may need to insert the end of a coat
     hanger into the hole to pull the end of the fish tape through the hole.

 

you encounter a fire block, proceed with Step Six. If you do not encounter a fire block, go directly to Step Seven below. 

  

Step 6: Running Cable Past a Fire Block

Running Cable Past a Fire Block

A fire block is a horizontal beam of wood running between the wall studs. You can drill a hole through the fire block or create a notch to accommodate the wire.

 

To drill a hole:

 

1.  Insert a long flexible drill bit through the opening for the electrical box and position      it on the center of the fire block.

 
2.  Drill through the fire block.

 

To cut a notch:

 

1.  Cut into the drywall at the location of the wall block. 


2.  Use a sharp chisel and a hammer to cut a 3/4 in. wide by 1 in. deep notch in the      fire block as a conduit for the cable. Pull the cable past the fire block following the      instructions in Step Seven below.

 
3.  After you have fished the cable through the notch, cover the notch with a metal 
     nail plate to protect the cable from nail damage.

 
4.  Patch over the drywall hole. See our Patching Large Holes in Wallboard Project     
     Guide for step-by-step instructions.  

  

Step 7: Pull the Cable Through the Wall

Pull the Cable Through the Wall

1.  From the attic, basement or crawl space, use electrical tape to secure one end of
     the cable to the hook on the fish tape.

 
2.  At the wall opening, carefully and steadily retract the fish tape, pulling the cable to
     the wall opening. Be careful not to create friction that can tear the cable’s
     sheathing and avoid kinks that could damage the cable.