The Ultimate Guide to Running Wires Through Finished Walls

Let’s face it! Adding or extending an electrical circuit is no easy feat, especially if you have no one to help. In fact, it is a complex project. And it takes you to be immensely mindful while executing the job.

Running new electrical wires or pulling wires through finished walls can mean pulling no more than a few feet of cable to the extra outlet. Or you may choose to pull dozens of feet of cable.

At first, you need to spot the wires in your wall with a stud finder. Make sure there are 16 to 18 inches of standard height above the floor while running new electrical wires.

In this guide, we will talk about the steps of running wires through finished walls in a way that you can understand. Whether you are looking for commercial electrical services or a domestic electrician depending on the project type, make sure you go through the post first to have a better insight into how to proceed.

How do you spot a load-bearing wall?

It involves intricate planning while running electrical wire in a remodelled second-story property or a basement service panel. You may need to remove and patch drywall in the ancient space of the house. Do this technique carefully by creating a channel in the finished wall surface. You just need to ensure that you remove as little drywall as you can.

Before getting started

It needs you to have some basic understanding of circuits when you intend to run new electrical wires through finished walls. If you know the basics, you can easily find the right cable for installing the wires.

For this job, you will find a sheathed cable (also known as non-metallic or NM) cable, or Romex suitable. They are designed specifically for these kinds of circuit configurations & amperage loads.

If you are dealing with a 15-amperage loaded circuit, then you should go for a 14-gauge wire. And if it is a 20-amp circuit you are working with, a 12-gauge wire would be the standard.

The cable for a simple receptacle outlet circuit will usually have two conducting wires including a black hot wire and a white neutral. It will also include a bare copper grounding wire.

A label on the cable saying “12-2 with the ground” would be there. The labels simply mean it is a 12-gauge wire with two conductors and a grounding wire.

However, if you have a circuit with three-way switches, or you use it for certain light fixture configurations, you may need 3 conducting wires and a ground wire to ensure proper installation. Remember that these three-wire cables include 2 hot wires – one red and one black, a white neutral wire, and a bare copper grounding wire.

If you run a cable through the walls that have no finished surfaces or when you need to mount it right on the surface of the wall, you may not be able to use an NM cable.

This means it is best for you to run the wires through plastic or metal conduit. Or you can also make use of metal-sheathed BX cable.

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What are the safety considerations that you need to keep in mind?

Running or connecting new wires in some municipalities needs the contractor to obtain a building permit along with on-site inspection permission. Sometimes, it can be done by a DIY electrician (given that they perform the work in their home only). Once in a while, obtaining a permit becomes important for homeowners while conducting a short electrical examination.

Note: You should not ignore these two processes. The purpose of these processes is to ensure safety while conducting any electrical work.

While running a new electrical wire through walls, you will need the below-mentioned tools and materials:

  • Non-contact circuit tester
  • Circular saw featuring masonry blade
  • Pencil
  • Drywall saw
  • Straightedge
  • Stud finder
  • Safety glasses
  • Shop vacuum
  • Tape measure
  • Wire cutters
  • Drill with a 1/2-inch bit
  • Hammer
  • Dust mask
  • Tools for drywall finishing
  • NM cable
  • Cable clamps and staples
  • Metal nail guards
  • Drywall screws
  • Drywall joint compound
  • Drywall joint tape

The method of running electrical wiring

For those seeking ways to perfectly run new electrical wires, we have decided to discuss what we believe is important for you all to know. Below we provide a rundown of how to run new wire in a finished wall:

#1 Make sure the power is off

Safety is the biggest concern for homeowners. To ensure the same, it is important to turn off the circuit breakers first (circuit breaker that controls any live wiring in the same wall you will work). To ensure the power is off, take a non-contact circuit tester and apply it on nearby switches or outlets.

During the process, make sure you wear a dust mask and safety glasses.

#2 Work on the wall

For running wire through finished walls, carefully cut through the surface layer of the wall so that you find the studs there. As you do so, mark cutting lines across the wall. Continue doing the process from the electrical source to the destination box.

The aim here is to take out as little drywall as you can. Make sure the drywall section you have newly removed is wide enough so that you can bore new holes in the studs using a drill.

6 to 12 inches of drywall will do. Once you are done marking, cut out a new section of drywall with a drywall saw.

While running wires vertically, you will cut out and remove the entire vertical section between two studs. Then you need to spot the studs with a stud finder. Once you are able to remove a vertical section of the drywall, that is when you start installing the wires.

Expert’s comment:

Cutting away walls made with plaster and lathe can be difficult. But if you use a circular saw featuring a masonry blade set approximately 3/4″ deep, your job will be easier. In this case, cut horizontally along the wall while cutting through the plaster to remove a section of the wall. Then when you are done with the wire installation, you can use drywall to repair the wall. It will be as good as new.

#3 Bore holes

Start by drilling a 1/2″ hole near the centre of the studs, right where you will run the NM cable. Make sure the holes are at least 1 1/4” from the front surface of the studs.

It is preferred that you take a straight line while drilling holes. If the line is not straight enough it will be harder to pull the wire. You can easily bore straight holes by holding the drill inside the stud cavity while drilling horizontally through the studs.

Once you are done drilling holes, vacuum out the sawdust and wood chips.

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#4 Move on to cutting and pulling the cable

After taking a proper measurement, make sure you cut a suitable length of wire to run from the source to the destination. While cutting the cable, ensure there is a full foot of additional wire at each end. Pull the wire through the first stud and then the next stud, across the wall cavity. Continue the process until you are finished.

It is important that you first unravel the coil, straighten out the cable and then pull long stretches of wire.

Expert’s comment:

If you are running the wire from upstairs to downstairs through the floor plates, take a drill bit extender so that it will be easier to drill holes.

Use fish tape for pulling the wire as well. Expert commercial electrical contractors in London prefer using fish tape for pulling wire vertically. This is because it does not cause the drywall to be removed altogether.

#5 Attach metal nail guards

It is helpful to place metal nail guard plates over the edges of studs. This helps you to prevent accidental penetration of nails or screws into the wiring. Nail guards are also helpful in reinforcing the studs’ strength.

While according to the code regulations, there is no need to place nail guards as long as there is a 1 1/4″ setback between the holes. However, installing nail guards is an important safety measure that everyone should consider taking.

The electrical code regulations need homeowners to ensure that the wires are firmly anchored within 8″ of their respective electrical box and if they are installed vertically then there should be a 4 1/2 feet space between the electrical box and the cables.

#6 Patch the wall

Finally, you need to patch the wall where it was first channeled out. With the help of a straightedge and utility knife, carefully cut a drywall surface; insert it in the open drywall surface to attach it with screws to the studs.

How to determine if you can drill into a wall to create holes?

Before you start drilling into the wall, check the wall for any obstructions that may get in the way. Depending on the position of the outlets and light switches, you can detect where studs, wires, and pipes are. Experts advise using a digital detection device as they are more useful.

Do you need to open the walls to rewire a house?

No, there is no need to tear down the walls if you intend to rewire your entire house. All you need is to create some holes in the drywall. However, if you are after a full rewiring, relying on professionals is your best bet. This is because he or she knows the job better and will do their best.

How do you determine whether you screwed into any live wire?

It may prove fatal if you accidentally screwed into a live wire. This is where a digital detection device comes to your aid. For safety measures, it is best that you thoroughly inspect the wall with a digital device. In the unlikely event, when you end up screwing into a live wire, there will be no power to the outlet. You can determine if this has happened by using an AC voltage meter.

When do you need a professional?

Whether it is a new or extended circuit, running a new NM cable is not that difficult. However that does not mean that connecting the final hookup of outlets, circuit breaker, and switches require specific skills and expertise.

This is where professionals are important. If you are dealing with such things, make sure you hire an expert electrician to complete the final connections. In most cases, if not all, a licensed industrial electrician in London is mandatory to perform service panel work according to the needs of the local code. Also, if it is a more complex or long cable that you are trying to run through finished walls, call an electrician to ensure maximum safety, and results.

Our Electrician at Electric Works London provides commercial, domestic and industrial electrical services at affordable price. Do reach out to us if you want to learn more about how we can help you.

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