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I have an interior outlet. I would like to place an exterior (GFI) outlet in approximately the same position on the outside wall. How should I do that?

approx. loc. of desired outlet-|
-------------------------------------------------------- [Exterior of wall]

------------------------------[ ]----------------------- [Interior of wall]

                        current outlet


  1. What's the best way to locate and cut the exterior hole?
  2. What's the best way to cut into the existing wiring?
  3. Any considerations for exterior mounting?
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up vote 10 down vote accepted

You have a fairly simple project. Assuming you intend to tap the interior outlet for power, here are the steps and materials:

  1. First, check that you have enough room in the interior outlet box to introduce one new piece of 14/2 or 12/2 NM, whichever is the same size as in the box now. I will assume you know how to make a parallel electrical junction in the interior box.
  2. Next, run that short piece of wire through a clamp in that box, across/through the wall cavity and out of a 1/2 to 3/4 inch hole in the exterior wall close by. I don't know what kind of siding you have, so I can't tell you exactly how to make the hole, but a spade type wood bit works well on many types of material. Minor fishing of the cable will be required, but not difficult, especially if the interior box can be removed partially to improve visibility.
  3. Once you have fished the wire from inside the interior box to the exterior, made your interior electrical connections and secured the cable inside, caulk the exterior hole around the wire with silicon.
  4. Feed the wire into an exterior surface mounted box using the proper grommeted fitting. Caulk around the back edges of the exterior box with silicone (to make the back water tight) and fasten it to the wall.
  5. Now you can connect your new GFIC outlet and install your weatherproof cover.

Of course, use proper safety procedures: turn off power at breaker panel before working in the interior box and doing any wire connections. BTW, if you have vinyl siding, there are special exterior boxes that will fit nicely. These are available anywhere. I know this is a long answer and maybe a bit confusing, but it is really a simple task. Good Luck

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That doesn't sound too hard. One question though: Wouldn't it be better to run the wire to an internal housing with a weatherproof cover, instead of an entirely external housing? – morganpdx Feb 22 '11 at 19:19
That is an option, but you have to be absolutely sure it is water tight. A standard wall box will not work. A rain proof cover will not mate up to it. Water leaking into a wall can cause lots of problems. The type of box you are thinking of has a flange that can be caulked against the siding or has a gasket, and mates to the cover properly. – shirlock homes Feb 22 '11 at 22:01
Doresoom, thanks for the edit. Looks so much better. Thank you. – shirlock homes Feb 22 '11 at 22:03
Flange. Gotcha. Thanks! For the record, the siding is cedar shake. And thanks for the edit as well @doresoom ;) – morganpdx Feb 23 '11 at 18:52

Another thing to keep in mind as well is that you will need to have enough power available on your breaker. I.E. if your interior outlet is on a breaker with several other outlets and there are numerous things plugged into those outlets, depending on the amperage of the breaker for that room, it may be better to run a dedicated line. This would especially be the case if you are planning on operating any high amp drawing equipment by plugging it into the external GFI.

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Yeah, I'm taking that into consideration. I believe the circuit is fairly underused, but I intend to confirm that first. – morganpdx Feb 23 '11 at 18:53

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