Running wires through walls is required in many different scenarios: when installing TVs, speakers, networking, security systems, lighting, and new outlets without exposed cabling. Here is how to do this safely according to the NEC.

Before You Start: Safety & Code Basics

• Turn off the power at the breaker if working with electrical wiring.

• Check for studs, pipes, and existing wiring using a stud finder.

• Follow local electrical code (NEC in the U.S.). Permanent power wiring must be in-wall-rated cable (e.g., NM-B or MC).

Step 1: Cut Openings for Cable Routing

Cut openings for low-voltage brackets or electrical boxes to neatly and safely route cables between wall cavities.

Use:

• low-voltage mounting brackets for data or AV wiring

• electrical boxes for power wiring

Keep openings vertically aligned whenever possible to simplify cable routing.

Step 2: Confirm a Clear Path Before Drilling

Drill a small pilot hole to confirm a clear path. Check carefully for plumbing, existing wiring, ductwork, and insulation before running cable.

Step 3: Separate Power and Low-Voltage Wiring

Keep power wiring separate from audio/video or data cables.

If they must cross, do so at a 90° angle to reduce electromagnetic interference.

Never run power and communication wiring in the same box unless a divider is installed.

Step 4: Protect Wiring Inside Studs

Route cables through the centre of studs.

Install protective nail plates if wiring is closer than 1¼ in. to the stud face to prevent screw or nail damage.

This protects cables from drywall fasteners and future wall-mounted fixtures.

Note on the Difference Between Low-Voltage And Power Cables

• Power wiring must be installed in electrical boxes, grounded, and all splices must remain inside accessible junction boxes.

• Low-voltage wiring uses low-voltage brackets instead of boxes, must be separated from power wiring, and should use in-wall rated cable.

Running Wires in Different Situations

Through Finished Walls

Use fish tape or flexible drill bits to route wiring without cutting large sections of drywall. Small openings behind devices or wall plates minimize repair work.

From Basement to Wall

Running wiring from the basement is often the easiest method:

Just drill into the bottom plate, fish the cable upward into the wall cavity, and pull toward the device locationю

From Attic to Wall

Attic access allows for simply dropping cable down into interior walls without horizontal drilling.

Horizontally Through Walls

When routing sideways, be sure to drill through stud centres. Also, maintain proper depth from stud edges and install nail plates if needed.

Horizontal runs are common when relocating outlets or running speaker wiring because devices are often not vertically aligned.

Through Exterior Walls

Exterior wall wiring requires extra care because it serves as the house's thermal barrier. Be sure to drill at a slight downward angle. Seal penetrations with exterior-grade sealant and avoid compressing insulation

You will commonly use this method for outdoor devices like security cameras and lighting.

Extra Tips for Clean & Professional Results

• Use in-wall rated cable (CL2/CL3) for speaker & AV wires

• Leave extra slack for future changes

• Label cables before pulling

• Install recessed outlet kits for wall-mounted TVs

• Seal openings to maintain fire barriers

Choosing the Correct In-Wall Cable

Always use wiring rated for permanent installation inside walls.

Electrical Power

• NM-B cable

• MC cable

• THHN conductors in conduit

Networking

• Cat6

• Cat6a

• riser or plenum rated where required

Audio / TV

• CL2 / CL3 speaker wire

• in-wall rated HDMI

• RG6 coaxial cable

Low-Voltage Control

• thermostat wire

• doorbell wire

• LED lighting cable

Never run extension cords or appliance power cords inside walls, as they are not designed for permanent installation and pose a fire hazard when concealed.

Minimizing Drywall Cutting

To run wires without opening large sections of wall, use helpful strategies. Instead of a new hole, you can use attic or basement access. Fish cable through existing cavities and cut only behind devices or plates. If you are worried about future upgrades, conduit or pull strings can simplify the process.

If you add new circuits or route through structural members, contact a licensed electrician to finish the job. An electrician is also a must if permits are required.

Nassau National Cable sells a wide range of in-wall wiring solutions, including NM-B and MC cable, THHN/THWN building wire, SER/SEU service entrance cable, fire alarm cable, and multi-conductor communication cables.