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For soundproofing applications, they make acoustical putty that you put around the electrical box. However, what if you can't get behind the electrical box? In my case, I have a wall floating on hat channels about 3" from the studs. The electrical box I will be using is an old work box with a clamp that allows the box to be fastened to the drywall rather than studs. This means that I will not be able to get to the backside of the box to apply the putty. I though about putting it around the outside of the box before sliding it through, but that doesn't seem like it would be very stable.

This leads me to me idea of putting the putty on the inside. I uploaded pics of a mock application. The outlet fits well and I think there would be plenty of room for the wires. I know next to nothing about electrical, though, and I worry about not accounting for things that might not play well with the putty.

Does anyone advise against this? I hope not because it's really the only way I can do this.

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Update:

Here's what I ended up doing. At first, I had a hard time understanding Evil Greebo's diagram, but I think this was the general idea he was conveying.

First, I cut out the smaller hole for my outlet. Then I cut out the entire section 2" around the outlet hole.

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I installed some support boards on either side of the opening.

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I used an old work box with adjustable flanges and installed it into the cut-out.

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I then covered it with my acoustic putty (QuietPutty) and left an opening for the wires. Looks like some kind of alien organ, doesn't it?

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I ran the wires into it and then packed the putty tightly around the wires for good measure. A flathead screwdriver worked great for packing and manipulating the putty.

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Finally, I placed the section into the wall and screwed it into the support boards. My pic only shows two screws, but I actually screwed in all for corners.

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If anyone else can think of a better way to do this, let me know because I am about to do it again, but this time with 5 outlets, one of which is a two ganger.

oscilatingcretin
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2 Answers2

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As per the comments, no, it's not a good idea.

The box / soundproofing should have been installed before drywalling. If you want to do it right, cut a piece of the drywall out to give you room to work and install it properly, then close up the wall again.

The Evil Greebo
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Given the previous issues listed with the other answer:

Get one of these style boxes.

enter image description here

Open the drywall up enough that you can put a 1' 2x4 behind the wall. Mount the 2x4 to the drywall with a drywall screw placed every 3" along that 2x4. The first 2x4 should be completely covered by the edge of the drywall.

Take a SECOND length of drywall and mount it to the first one, so that it is exposed through the hole. Connect it to the first board using several screws.

Wrap your new box in acoustical putty and mount it to the 2nd board.

Close up the opening by attaching replacement drywall patch on one side to the exposed stud, and on the other to your hat channels.

Then you'll have support boards fixed to the silent side of your wall, and your box, wrapped in putty, will be connected to those boards.

See pic:

enter image description here

The Evil Greebo
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