Adding outlets to an existing in a garage

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Jan 25, 2017
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Northern California, bay area
Hi, I’m needing to add multiple outlets in my garage for convenience purposes mainly. The garage was once 3/4 a bedroom with a small section up front for my tools and such. What would be the desired, most economical way to do this? I don’t mind patching some sheet rock- it’s no Taj Mahal.



Well-Known Member
Nov 24, 2021
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Depending on your layout & if you want to draw heavy current, you might tap your new wiring off the existing outlet that is farthest upstream of the existing string.


Active Member
Feb 24, 2021
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As Guzzle noted, adding receptacles to an existing circuit can be tricky. You need to review the maximum amperage drawn by what may be plugged into the receptacles. For example, do you plan to use power tools in your garage, a pressure washer, etc? What else might be plugged into the same circuit in the bedroom, e.g. a sound system, bigscreen TV, computer, etc? Standard residential circuits are 15 amps, and this applies to both the breaker and the wiring in the circuit. You cannot simply install a new 20 amp breaker on a circuit run with 15 amp wiring, for example. You may need to install a new circuit in your main panel to support new receptacles -- a job typically done by a professional electrician. The new breaker for the new circuit will need to be AFCI.

Also check to see if the lights are connected to the same circuit as the receps. One way to reduce amperage a bit is to replace any incandescent bulbs with LED.

When you run new wire for circuits in the new walls, I disagree with the person who suggested exterior wire mold. It is simple to drill holes in the studs and run new Romex cable in a wall, which will also give you a standard, professional result. Read up on the Web on the details for how the cable needs to be fastened with a staple near every receptacle, and how no sharp bends should be made in the cable. Also read up on the correct way to wire a receptacle box, and buy the largest hard plastic shelled box available for your 1 gang or 2 gang receps. And read up on the best way to wire a receptacle, e.g. with short 'pigtail to the receptacle. Lots of resources are available on the Web.

The holes in the studs also need to be fire-stopped by filling them with fire resistant sealant, e.g. 3M CP 25WB, which is available at Home Depot and Lowes. DO NOT use canned spray foam, even if it has "Fire Block" on the label. These foams are very flammable after they cure, and will ignite at just 240 degrees F -- significantly lower than the ignition temp for paper or wood.

Your new walls also require 'fire blocking' -- pieces of 2x4 mounted horizontally to block / slow the spread of flame. See, for example: The exterior walls also need to be insulated. I recommend using rock wool, which delivers R-4.1 per inch of thickness, is much denser than fiberglass and is fire resistant.

Finally, your addition and wiring should be inspected by your local town / city building inspector. The wiring needs to be inspected while the wall is still open. Your insurance company may deny coverage, for example, if a fire starts in an uninspected garage addition. This means that your work has to follow the building and electrical code, e.g. the number of receptacles per foot along a wall, how the wiring is run (fastened with no sharp bends), etc. So it would be a good idea to read up on the details, as I noted above.

I hope this is helpful,


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