Home DIY How To Extend an Exterior Electrical Outlet

How To Extend an Exterior Electrical Outlet

How To Extend an Exterior Electrical Outlet

Our back patio had one single gang outlet, which wasn’t in a great place and was definitely seeing the effects of time. The grip on the plugs was sloppy at best and only having a single gang outlet made it problematic if multiple tools were needed at once.

I installed a slat wall in front of the outlet that only made things worse. Now, in addition to being an overall bad outlet, it was also far less accessible!


The plan, then, was to extend the outlet to the front of the slat wall, making it far more accessible. Along the way, I’d upgrade it to a double gang outlet to double my ports and use new “professional grade” outlets to hopefully last in good condition for longer.

First Video!

I also made the first video for granworks all about this project! Check it out here:

The Overall Plan

I used this opportunity to finally experiment with flexible “liquid tight” conduit. I looked very easy to work with, but I never had. I also spent quite a lot of time researching how I could attach the conduit to some kind of box in front of the original outlet box before finally realizing that a “lamp holder cover” would work perfectly.

Here’s my collection of tools and parts:


Note the printed out circuit breaker map — that’s absolutely essential. Not pictured is the 12 gauge THHN wire I used for the conduit chase.

The Pre-Ritual

My very first action is something I do on all electrical projects after getting zapped far too many times. I get out my trust multi-meter and verify that the voltage is 120v. Doing it up front tells me that my multi-meter has charged batteries and is working correctly. I then go to the circuit panel and flip the breaker. After that, I go back to the outlet and repeat the test with my multi-meter to ensure that the voltage is now zero.

I do it in that order because I have had cases in the past where my multi-meter had dead batteries and the voltage indicator lights didn’t light up. In that case, I thought the power was dead and the multi-meter seemed to confirm it… but when I actually started work, the resulting jolts informed me that the power was still live!

So now, by verifying the live power beforehand, I can actually trust my multi-meter when it stays that there is no power!

Starting on the Original

I unscrewed the original watertight cover from the single gang box. It wasn’t very watertight anymore — most of what little foam was left just disintegrated. You can see from the picture that it has started to crack in places, too.


The picture doesn’t show how sloppy each of the slots are. It’s not a nice outlet by any stretch of the imagination.

Next up was removing the old outlet from the box, which should have been trivial. Nope. It took maybe five minutes and applying some serious leverage to get it out. The problem is that the screws holding it in were “stuck” in an odd way. They would both spin freely, but would neither advance (like there was no threads) nor would they just slip out (like something was holding them). I finally had to almost rip them out.

Once the outlet was out, I could see just how non-tight the old cover had been. There’s so much dust and cobwebs inside that it wasn’t possible to see which wire was white and which was black at first.


I discovered that the original wiring was 12 gauge, which surprised me because nearly all of the old wiring I discovered in our house to date has invariably been 14 gauge (even though most circuit breakers are 20 amp). Curious.

I spliced on my 12 gauge THHN black, white, and green and then tucked them in place.


I chose a three hole lamp holder cover since once of the holes was already going to be facing roughly in the direction of my new outlet box. That saved having to buy another 90 degree liquid tight connector. The cover came with plugs for the two unused holes, which was handy.

It was very mildly a pain screwing on the new cover if only because the gasket kept obscuring where the bottom screw was supposed to go. It was trivial to attach after finding the right starting point, though.


I had never worked with liquid tight flexible conduit before and was excited to try it out for this project. It exceeded my expectations on ease of use!

The conduit itself can be cut easily with a utility knife (no special saw like with PVC or EMT). The connectors all fit together very similarly to EMT-style compression fittings, so no special tools or glues are needed there, either.


Basically, you start by cutting the conduit to size with a utility knife. Then you unscrew the cap of the connector and slip on the conduit. This leaves a “channel” in the other half of the connector that you can very easily press the conduit into. The cap then screws back on to the connector and in doing so creates a water tight seal. Nice! Really, the only downside to liquid tight conduit is that it’s quite a bit more expensive than PVC or EMT. At my local box stores, 1/2″ PVC runs for about 15 cents a foot, vs 23 cents a foot for EMT and up to 40 cents a foot for liquid tight!

After attaching the first connector, it’s a trivial matter to stuff the wires through the conduit and screw it all into the lamp holder cover.


Yes, after doing this, I regretted getting a “bronzed” cover — a grey cover would have matched a lot better!

The New Double Gang

I got a metallic waterproof outlet box to hold the new outlets, since they were made to accept the water tight gasket covers. Unfortunately, they are designed to be screwed into a wall behind them and I needed to screw them into the sides of my slat wall. That necessitated drilling some holes into the side of the box.


I used galvanized structural screws to make the attachment, since the slat wall wood is pressure treated. Those screws are specifically rated for use in PT lumber.


The box came with three holes — one on each the top; back; and bottom. I plugged the top and bottom and only used the back. You can see in the above photo that I also did screw in a ground screw just to tie all of the grounds and metal together.

I attached the conduit to the new box using a 90 degree connector. It was identical to the other connector. Although… I did have a brief hiccup in that I forgot to slide the connector cap onto the conduit. Oops! That required pulling the wire back out of the box and disconnecting the connector before redoing it all. Not that big of a deal.

I also had a bit of an issue with the length of the conduit. For some reason, I measured it to be a good two inches too long. On one hand, it does cut very easily with a utility knife. On the other hand, the conduit already had the wire in it and I don’t like cutting conduit with wire already there. One option was to back out every part of the conduit; cut it to size; and re-do it all… but I didn’t want to go through that much effort. So I cut the conduit down to size with the wire in situ just being very very careful where I was cutting with respect to the wires. I’m happy to report that I didn’t nick the wires at all!

After connecting the conduit and fishing through the wires, I was able to screw the new box into place. We can finally start seeing hints of what this going to look like in the end.


These next photos are screen caps from the video since I completely spaced on taking photos of the wiring process. No idea what I was thinking (or not thinking).

I typically work in new boxes by splicing on pig tails to the line wires. This gives a lot more flexibility with the outlet placement and also allows outlets to work individually, even if one of the neighboring boxes fails. Boxes wired in serial will also fail in serial. I didn’t do it that way in this case, though, for no particular reason. I had the room; the wire nuts; and enough wire… but just didn’t feel like doing it that way this time around.

In this case, I just cut and stripped the power and neutral wires to size and looped the ground around the ground screw. The ground was then pig tailed with two more since there wasn’t the easy “jumpers” between the outlets for the ground like there is for the other wires.


The outlets were then connected to each other, with black to black and white to white. I always remember which goes to which by the colors. Brass starts with a “b” like “black” so I remember that one and then I guess silver is kind of like white… but in reality, I only ever remember the “brass is black” one and the other must be white. Ground is always ground.

I always get “professional grade” outlets even though they cost a bit more. That’s because it’s trivial to insert a stripped wire into a slot in the back of the outlet and then screw it down tight. This is permanent until it’s unscrewed and then the wire comes out very easily. In the less expensive outlets, you either need to wrap the wire around a screw like you do for the ground wire (which is tedious) or you can insert a stripped wire into a hole, but it’s a one-way operation. I like the flexibility and easy of use of the professional grade outlets enough to justify their higher cost.


Sealing it Up

The outlets aren’t actually screwed in place at this point. Instead, the foam gasket is slipped over them and then the screw goes through the gasket first and then the outlet holes. The screws need to be proud by maybe a 1/4″ or so for later. So in this picture, the outlets are loose still somewhat.


And right now some of you are likely yelling at the screen “why aren’t you using GFCI outlets?!” Well… because I don’t have to. This entire exterior circuit is already GFCI protected so it’s unnecessary to make every single outlet one. I would still do so if these were extremely exposed outlets, but they’re not. They are normally going to be in a waterproof cover and even when not, they are under a patio that is a good 10′ wide. Even the most driving rain doesn’t come close to touching the area where those outlets are. All in all, the extra cost of individual GFCI outlets wasn’t justified in this particular case.

Okay, back to the narrative, already in progress. The cover for the new box has these key-hole slots that fit right over the protruding screws from the previous step.


It was pretty straightforward to fit the cover over the large hole in the slots; push it down into the foam gasket; and slide it over. At this point, I tightened all the screws and everything fit solidly into place.

And that was it! I have a fully extended and upgraded outlet.


Nice! It’s rock solid and the new outlets are much nicer to use than the old one while being far more accessible.

Oh, and one bonus shot of my work area while doing all this. I’m not one of those guys that cleans up as he goes.



    • It’s a Commercial Electric CE-HGT6120 “Shock Stop Tester” that I bought at Home Depot for $10 or so. I see that there is a rebranded Sperry version with the same code and looks identical but at twice the price. Not sure what’s up with that.

  1. Can this procedure be done for say the inside of a garage? I need power at my workbench. Also what brand of box and cable did you use on both ends?

    • In general, yes. I wouldn’t personally use these specific components inside of a garage, though. They don’t need to be water-tight and may require extra protection against impact. So when I wired up my garage, I used EMT conduit between standard punch-out style electrical boxes. If my garage was made of wood, then I would have just done all the wiring inside of the wall itself. The method I showed in this post was essential only because I was dealing with a block wall (couldn’t go behind it) and it was exposed to the elements (needed to be weather-tight).

      And sorry, I don’t remember the details of the components I used at that level, beyond what I wrote in the post. This was over two years ago. It was whatever I found at my local Home Depot or Lowes.


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