I need to drill a 1 inch hole in a basement foundation block wall to pass a 1/2 emt conduit through. How do I seal the gap afterwards to pass inspection, prevent mice, insects, rain and drafts.

Keep in mind it's winter in Minnesota, so any compound needs to be able to be applied in cold conditions.

Do I simply use duct sealer or something more solid.

  • Do you have any water leakage issues? – Ed Beal Jan 10 '19 at 20:29
  • No, but the hole will be on a vertical face of the north west wall so it will get full exposure to wind and driving rain – bfoddy Jan 10 '19 at 20:49
  • The hole will be about 4 feet of the ground in the walkout portion of a walkout basement – bfoddy Jan 10 '19 at 20:53
  • if you are worried about mice digging through the duct seal, then jam in some steel wool between the conduit and the concrete ..... mice do not like to chew steel wool – jsotola Jan 11 '19 at 2:13

I'd use duct seal. I don't think mice like chewing it much, and at four feet up it's fairly safe anyway. Keep it in your pocket until you're ready to apply it.

You could also use pure silicone or urethane caulk if the masonry is dry. Both are solvent-based and should still work fine in the cold.

  • I just want to make sure duct seal stands up to all the weathering factors of sunlight, cold, rain, etc for the long term. A power line entrance right next to the hole seems to be sealed with something harder. – bfoddy Jan 10 '19 at 21:36
  • That's what it's for. It does tend to harden over time. – isherwood Jan 10 '19 at 21:38
  • Duct seal would work great since its on a daylight basement I wouldn't be two worried, if it leaks it would not be hard to arrange some drainage. – Ed Beal Jan 10 '19 at 22:32
  • I'll try it this weekend – bfoddy Jan 11 '19 at 22:00

Besides duct seal and caulk, you could use a two part epoxy putty that bonds to both metal and masonry.

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