DIY a Built-in Extension Outlet

I've received a couple of emails asking how we converted a wall outlet into an extension outlet for our TV room sofa table. This outlet, built into the face of the table, allows us to utilize the electrical outlet that is behind the couch - without having to move the couch out of the way. I managed to corral Tom long enough to have him show me what he did.

I shouldn't have to mention this, but if you are not comfortable/knowledgeable about working around electricity and electrical outlets, do not attempt to install this yourself.

Update: We recently upgraded to an outlet with built-in USB ports, and I asked Tom to switch to a grounded wire at that time. Instructions are the same - refer to additional step for attaching third (ground) wire below.

For this reconstruction we used spare parts we had laying around, but I'll also intersperse the photos and instructions with what we did the first time. However, the steps are exactly the same.

Parts you will need:

Tools you will need:

If you're installing this outlet onto the face of a board - like a table - the first thing you'll want to do is cut a hole in the table the same size as the electrical box. Tom used a rotary zip saw, but you could also use a jigsaw.

When Tom installed the original outlets he used an airtight electrical box like this that had a frame around it.

He was able to screw the frame directly to the underside of the table. An airtight box wasn't necessary but it was all the store had in stock. If your electrical box doesn't have a frame, you can install a piece of scrap wood to the underside of your surface, and attach the box to it. That's what I'm going to show you here.

Fit the electrical box into place and hold the scrap wood against it, along the side of the box with the bracket.

Drill pilot holes through your surface and into the scrap board. Make sure they are very, very close to the hole so that the face plate will cover them. 

Attach the screws so that your scrap board is held in place.

Flip your table upside down and set it on a stable surface like a workbench, or even on the floor. It'll be much easier to attach the electrical box without having to crawl under the table. Using the holes in the electrical box bracket as a guide, attach screws on each side so that the box is securely fastened to your scrap board. 

As I mentioned, if you are using an airtight box with a frame, you'll just use short screws and attach the box directly to the underside of your surface. You don't want the screws poking through the topside, so measure carefully. I prefer the look of the airtight box but you have to work with what you can find. And from the top it won't look any different.

Once your box is mounted to the board, you can work on attaching the wiring.  Take your extension cord and cut off the outlet connector (the socket end). Our outlet is only used to plug in lamps, phones, computers, etc., so we bought a light-duty 2-pronged cord, but if you are using your outlet for more heavy-duty loads or in wet areas, you'll want a 3-pronged grounded cord.

Take the cut end of the cord and split the two wire bundles apart. Using your sidecutters, a knife or wire strippers, carefully cut through the plastic sheath without cutting the wire inside and pull it off. You'll want to have about an inch of exposed wire. Do this on both wires. Twist each bundle of exposed wire tightly so that it isn't fanned out.

If you are using a grounded wire, there will only be one sheath. When you strip it off you'll find three more wire sheaths, white, black, and green. The green one is the grounded wire. You'll need to strip off an inch of each coloured sheath to expose the copper wire. It should look something like this:

source

Feed the two wires through one of the openings in the underside of the electrical box. The tabs are made of plastic, so you should be able to push them in slightly, enough to get the wire through. Pull the wire up through the front of the box so that you have enough to work with.

Your electrical outlet will come with 4 brass screws, 2 on each side. Tighten one on each side just to get it out of your way.

Take one of your wires and twist the exposed end around one of the (untightened) screws on the outlet. Make sure that you twist the wire in the same direction as you will be tightening the screw (usually clockwise). Tighten the screw down. Repeat this on the other side of the outlet.

 If you are using an extension cord with a third ground wire, attach that wire (which you previously stripped as above) to either the green screw in the bottom of the electrical box, or to the green screw that's right on the electrical outlet. Either place works, as once the electrical outlet is attached to the box the circuit will be complete.

Once your wires are attached, screw the outlet into the box through the holes at either end (the correct screws should be provided with your outlet). Attach your faceplate and you're done.

When we put the outlets in the sofa table we used a larger rectangular outlet versus the common outlet with rounded corners. These outlets require a slightly larger faceplate - which is beneficial to you if you're using the scrap board mounting method and need to cover up your screw holes.

Once Tom showed me how to install this outlet, I couldn't believe how easy it was. I'm terrified of electricity, but I think even I could do this without being afraid of zapping myself.

I'm thinking of attaching one to the side of my craft table so that I don't have to crawl under the table all the time to plug things in - the sewing machine, the Silhouette cutting machine, laptop, etc. I'm switching them out and moving them around all the time - this will make it a lot easier. Not to mention, I can move the table around and the electrical outlet will move with me.