How to Run Electrical Wires in a Finished Wall

Planning Your Wiring Project

Before cutting into any walls, take time to plan your wiring project. Here are some important steps:

Determine Your Electrical Needs

Decide what rooms need additional outlets or lighting and where you want switches located. Consider any large appliances or high-wattage items that will need their own dedicated circuits. This will help determine how much wiring you need to pull.

Map Out Wiring Runs

Sketch a layout of where your new wires will go and how they will connect. Measure wall lengths and outlet locations. Note any obstacles like HVAC ducts or plumbing pipes that could affect your access.

Choose Suitable Wiring

Select the correct gauge electrical wire for your needs. For 15-20 amp general household circuits, 14 or 12 AWG Romex cable is commonly used. Ensure your wire has an outer sheathing rated for in-wall use.

Gather Essential Tools

You’ll need basic hand tools like a drill, drywall saw, hammer, tape measure and screwdrivers. Specialized tools like a fish tape, wire strippers, voltage tester and wall stud finder will also be very helpful.

Consider Hiring an Electrician

For complex or whole-home wiring projects, hiring a professional electrician is highly recommended. They have the expertise to ensure all electrical codes and safety standards are met.

Cutting Access Holes in Drywall

To route your new wires through walls, you’ll need to cut access holes between wall studs. Follow these safe methods:

Locate Wall Studs

Use an electronic stud finder to detect stud edges and mark their locations. Studs are normally 16 inches apart. Avoid cutting into any stud during this process.

Outline Access Holes

Draw the outline of holes using a square and level to ensure straight cuts. Make them large enough to fit your hand and tools through.

Cut Drywall with a Saw

Use a drywall keyhole saw to neatly cut the hole outline. Make very shallow passes to avoid cutting through exterior wall vapor barriers or siding.

Use a Drywall Knife

Finish cutting inner layers of drywall by hand using a utility knife with long, sturdy blades. Remove cutout pieces carefully.

Consider Using Drywall Channel

For easier access, you can cut a channel between multiple stud bays using a router with a drywall channeling bit.

Fishing Electrical Wires

Once access holes are cut, you can “fish” your new wiring from bay to bay inside the walls. Here’s how:

Thread Fish Tape

Take the supplied metal fish tape and thread it through the wall cavity from an access hole to where a new outlet is needed. Use stiff wire to poke through insulation if needed.

Attach Wiring

Once the fish tape is through, attach the new electrical wire securely to the end with electrical or duct tape. Leave extra length for connections.

Pull Cable Through

Have a helper steadily pull the fish tape back while you guide the wiring to avoid snags. Don’t pull too aggressively to avoid damage.

Use Glow Rods

Alternatively, you can use LED glow rods and retrievers threaded into walls to visually see paths and steer wires around obstructions.

Protect Wires

When running wire over metal or wood stud edges, make sure to use conduit or plastic guards to prevent abrasion damage during pulling.

Installing New Outlets and Switches

The final steps are to connect your new wires to outlets and switches. Here are some tips:

Prepare Wire Ends

Carefully strip back the cable sheathing about 1.5 inches using sharp wire stripper tools. Strip just .5 inch of coating off wire ends.

Connect Switches and Outlets

Use screw terminals to connect hot, neutral and ground wires to new outlets, switches and light fixtures. Double-check connections are tight and insulated.

Mount New Outlet Boxes

Attach new plastic outlet boxes securely to studs at desired heights. Feed wired-through cables into these boxes for connection. Use metal nail guards if needed.

Secure Devices in Boxes

Once wired up, tightly install each outlet and switch into its box using provided mounting screws. Attach wall plates flush to the drywall surface.

Test Circuits

Turn the power back on and test each outlet, switch and light to make sure they operate correctly. Use a voltage tester to confirm power at outlets.

Safety Tips

  • Turn off electricity at the main breaker panel before starting. Use a contact voltage tester to double-check power is off.
  • Handle exposed wiring with care and always cap unused wires with wire nuts.
  • Ensure cables do not contact sharp stud edges, pipes or ductwork. Use conduit or edge guards if necessary.
  • Do not overfill boxes with excess wire, as this risks insulation damage and overheating.
  • Label all new circuits clearly at the breaker panel and outlet boxes.
  • Check for fireblocking between wall studs and reseal any removed material when complete.

Running new wires in finished walls takes time and care but can greatly enhance your home. With the right planning and precautions, this is a DIY project many homeowners can tackle successfully. If in doubt, consult an electrician for advice or assistance. Take things slow and be mindful of safety, and you can enjoy the benefits of rewiring without the headaches.

Frequently Asked Questions About Running Electrical Wires in Finished Walls

Can I run wires inside air ducts rather than through walls?

No, it is usually against electrical code to run wiring inside HVAC ductwork. The proper method is to drill access holes between wall studs and fish cables through the void spaces.

What if there is blown-in insulation inside my walls?

You can carefully bore a narrow channel through the insulation using a long drill bit or screw auger bit to create a path for fish tape and wiring. Just be cautious not to tear vapor barriers.

Is it okay to just run wires under the baseboards?

While simpler, this is not usually recommended. Exposed wires under trim boards can be damaged and also present a fire hazard. It’s better to conceal and protect cables properly inside walls.

What is the maximum number of wires I can put in one outlet box?

The National Electrical Code limits most standard outlet boxes to holding no more than four to six electrical cables safely. Overcrowded boxes can lead to overheating.

Can I use 12/2 Romex cable for all my 15 and 20 amp household circuits?

Yes, 12 AWG wire may be used for both 15-amp and 20-amp 120-volt branch circuits in residential applications according to code. The thicker wire gives you extra capacity.


Rewiring finished walls takes careful planning, the right tools, and attention to detail. But with proper precautions, even beginners can successfully run new electrical cables through existing drywall and finish with professional-looking results. Pay attention to circuit needs, use safe cutting techniques, fish wires neatly through cavities, and make solid connections. By following code and taking it slowly, you can safely upgrade outdated wiring or expand circuits in your home. Just be sure to call in an electrician if certain aspects seem overly complex or hazardous. With some diligence and care, those necessary electrical projects can be DIY.