Do you caulk inside of electrical boxes?


Old 09-20-16, 10:39 AM
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Do you caulk inside of electrical boxes?

Just as the topic says....especially ceiling / lamp boxes.
I can imagine caulking around BUT I would like to know if it is advisable to also caulk things like screw holes or cable entry-way etc....

If so, can you use Silicon caulk right on electrical cables ?
Are there any chemicals in the caulk that could damage/ dissolve external insulation ?

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Old 09-20-16, 11:08 AM
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No, no caulk should be used on the inside. You can (and should) caulk the crack between the sheetrock and the outlet box, and you can foam around the outside of the box if you have access from the rear, and you can use those foam insulators that go behind the cover plate, but no caulk inside. It provides little/no benefit, and would make a huge mess and aggravate anyone working in the box down the road.

If new construction there are many airtight box options.
Old 09-20-16, 12:28 PM
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Thread moved to Electrical Forum.
Old 09-20-16, 02:11 PM
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Some boxes need to be caulked or foamed around the back side depending on the fire or insulation rating of the wall they are penetrating. If you're in a fire rated wall or breaching a vapor barrier you should seal around the box with the appropriate sealant. They also make adhesive plastic-ish sheets and formed plastic domes that can seal around boxes which penetrate vapor barriers.

Common building sealants and insulations (silicone or acrylic caulk, urethane foams, duct putty) are all OK to contact cables.
Old 10-10-16, 10:19 PM
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Uh, this is really more of an insulation question than electrical, so I suggest moving it back.

Yes, anytime I've done work like replaced outlets or just removed faceplates for painting, I'll caulk boxes on exterior walls. I'll caulk where the wall meets the box and I'll caulk inside the box where the cable enters. Many older boxes have really leaky designs. It is kind of a mess to caulk the inside of the box, but it stops air leaks.

Actually I'll caulk boxes on interior walls too if there's a soundproofing concern.
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