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Can You Use A Junction Box To Extend Wiring

We know how exciting it is to install a new fixture. But it turns out you’re short on wires. We understand the chaos it can cause. Don’t worry, ‘cause we’ve got the answer to your question!

Can you use a junction box to extend wiring?

Yes. You can definitely use a junction box to extend your wiring. To do this, start by turning off the power. Then inspect the place and cut the required openings. Next, position the wires and adjust the box to pass the wires through. Lastly, put the box in and connect the wires.

Well, this is just the preview, but hold on, there’s more! So, grab your gears, and let’s get to work!

Why Use A Junction Box And Not An Alternative

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Wiring issues with hot tubs, water heaters, and several electronics can seem quite complicated. A simple junction box can often be a lifesaver in these cases.

Well, the alternative to using a junction box is wire splicing. Which is against the wire code. The reason being- if not done properly can cause a fire. Not only that, it can burn down your entire property.

If there are any damages from such wiring, your insurance won’t cover it. This is because such work is completely illegal.

In case, you really want to try this, do it at your own risk!

Here’s a quick guide to splicing wires behind the wall:

  • Use the wire nuts and wire behind the wall to make a connection.
  • Then twist the wires properly and connect them.
  • After that, push the wires behind the wall and close the wall.

There’s another reason why you shouldn’t do it. That is, suppose in the near future, you sell the house to somebody. The new owner might not be aware of this wiring, thus causing problems. 

It might be hard to detect such modifications. You wouldn’t want a faulty outlet ruining the entire connection for you!

These are some of the reasons why you should use a junction box!

How To Install Junction Box To Extend Wiring

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This part of the task might be a tricky one. But it’s nothing you and your DIYer self can’t do. All you need is a steady hand and a good junction box, and you’ll be good to go.

To make your project a little easier, here are our top junction box picks:

MICTUNING 7 Way Electrical Trailer Junction BoxCheck current price
LeMotech ABS Plastic Dustproof Waterproof IP65 Junction BoxCheck current price
Ogrmar Plastic Dustproof IP65 Junction BoxCheck current price

For the installation part, you’re going to need a few tools. Let’s look at our list:

Now that we’ve gathered our essentials, let’s get to installing!

Firstly, Turn The Power Off

It’s important to make sure your power is turned off. Because if it’s a bad day, you can receive an electrical shock.

You can do this in two ways basically. One, you can go for the circuit breaker. Or second, just turn off the switch of that particular wire If things go south, that might be the end of your journey in this world.  

It’s crucial to turn the power off and then start the work.

Inspect The Wall with A Wire Tape

This step is done to find out where the wires are routed. And mark the position of where to put the junction box.

What you’re going to do is, push the tape in both left and right. Then mark the place where it hits a dead end.

You’ll find two spaces, one for the spur and the other to place the box.

Trace And Cut Spaces For Junction Box And Spur 

Now, put the junction box on the marked spot on the wall. Then make an outline of it. Make sure to use a leveler to level it and trace! Because we don’t want a situation like a deformed mirror.

Then take a utility knife and cut out the traced section cleanly. After that, use your saw to cut the inner portion of the traced area.

Now, carefully take out all the debris and clean the entire part. Use your saw and hand to do this.

After that, trace a straight rectangle on the side. Taking the saw and utility knife, cut a hole in the wall. This opening on the wall will be for the fixture installation. Basically, keep a steady hand and use the saw as you’d use Dremel to cut ductwork. Even and straight!

Position The Wires in The Openings And The Box

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Now, take your new wire and push it through the box section onto the spur. Then take out the wires from the original wire section. Next, pull it out of the box part.

Make sure the cable is the same insulation, diameter, and larger in length.

Adjust The Box And Push Into The Wall

For the box, you need to take off two sections. You’ll see at the bottom, there are four parts to push the cable in from. So, take two of the parts out from each side.

After that, take the two wires and push them through the box. Then, gently push the box in as well.

Now, tighten the screws. If it’s done right, the clips on the side will go up. And the box will be placed.

Connect The Appropriate Wires

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Here you’ve to connect the wires together with wire nuts. That is, you need to make a connection of the spur with the main circuit.

Make sure the wires are connected properly in the junction box. The green wires are connected together and bonded to the junction box case. Then do the same for the other wires.

Check if the wires are twisted properly before installing the connector. And then put the metal cover on to the box.

Make sure that none of the cables are exposed when finished. Then test the installation after all wires are terminated.

This is basically how you install the junction box.


Question: How many wires can be spliced in a junction box?

Answer: It depends on the size of the box. The smallest (2x4x1 1/2-inch) box can slice up to two cables. While the largest (4x4x2 1/8-inch) one can fit four to six cables.

Question: How many wires can you splice together?

Answer: You can spice three or more wires together. A pigtail type is the best for joining more wires. Make sure to have one or more wires straight and the others wrapped around them.

Question: Can you splice wires without a junction box?

Answer: Simply, no! All the spices must be in a junction box. And this box should be accessible. This is because wire splicing solely is against the wire code. 


With this, we’ll be parting ways. We hope this answered your burning question “can you use a junction box to extend wiring”.

If you face any problem, then contact a professional!

Until next time, take care!