During the cold days I noticed a little draft coming from the light switch next to my house door. Removing the switch revealed that the tunnel for the cables was widened to fit the cables for the electric strike control right next to it. The hole measures about 1/2" in diameter.

Is there a preferred way of closing this? By default I would either use the silicone caulk I have still around or get some expanding foam. As I am no electrician I do not know how accessible one should keep those wires. (Silicone caulk would be easier to remove as foam as far as my experience goes.)

Here's a picture

The socket and the hole

  • Can you post a picture? Is the hole right in the electrical box, or beside it? – Steven Apr 19 '13 at 19:05
  • Done. Hope that helps! – Lucas Hoepner Apr 19 '13 at 19:18

Sealing around wires and cables is usually a job for Duct Seal.

Duct Seal

I'm not sure of the availability of this outside the United States, but I imagine it or a similar product is available in most places.

Duct seal never hardens, so it can be removed, move, reshaped, and reused. It also will not react with the wire/cable in any way, which often a requirement in building and electrical codes.

  • Awesome stuff! Works like a charm! – Lucas Hoepner May 12 '13 at 14:38

Silicone caulk should work--you might try sealing around the switch assembly itself if you're concerned about trapping the wires themselves.

Alternatively, you could try to stop the draft elsewhere. That will involve using caulk and expanding foam elsewhere around the building to prevent airflow into the walls and around the insulation. This will have a much greater benefit, but it is also a much larger and more time-consuming project.


In the USA, they sell foam outlet cover gaskets that seal off the outlet box to prevent outside air from leaking through when you screw the cover over the gasket (I'm assuming you're not in the USA since that doesn't look like a standard USA switch):


Another option would be to use "firestop" putty - it's designed for exactly this type of situation: closing off conduit runs to prevent fire/smoke entry, but it will also stop air from leaking through. It's designed to stay pliable over time, so you can still remove it later to get to the wires if you need to. Also, it's non-flammable, so if the outlet overheats you can be sure it won't catch fire.


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