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All the sides of my house are paved, and I need to drive a new ground rod for an antenna.

Would it be against code (NEC) to drill a hole in the concrete to pound in a ground rod?

Bonus question: How big should the hole be, and is it okay to leave several inches of the rod above the pavement for accessibility?

  • I can't "legally" provide this as an "answer" on SE, since it'd doesn't directly address your specific question, but it may be valuable supplemental information. I don't think you'll want to drive a ground rod through otherwise continuous pavement because the soil beneath the pavement may be exceedingly dry and you may get a very poor ground. Been there, done that. If the ground rod reaches the lowest seasonal water table, it's fine, though. – TDHofstetter Aug 26 '14 at 13:04
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It is fine to drill a hole in pavement to drive the rod.

How do you attach clamps and wire if it is driven flush? My city inspector wanted to be able to see the manufacturer's stampings on the end of the rod to prove that I had not cut it off short (providing less than required soil contact), I was specifically required to leave several inches exposed.

  • Hmm... I see. So this means that it could pass inspection even if it is several inches above ground? I could use a 10' rod could mitigate the 8' soil contact rule in case there is a safety issue. Just a side note: the electrical work of the entire house needs to be redone, and the electrician may end up grounding to this rod in the future as it is right next to the meter. – user339676 Jul 27 '14 at 20:49
  • Go ahead and buy a large gauge (5/8"?) residential grounding rod if you anticipate grounding your electrical service to it. Avoid the thin short supplementary rods designed just for antennae. – Jimmy Fix-it Jul 27 '14 at 22:20
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    A hammer-drill is useful to drive the rod, you just chuck up on the end and drive it in. Check with your code enforcement authority regarding rod diameter and length (i.e. soil contact requirements) for your proposed new service panel, and whether leaving exposed rod will be acceptable. – Jimmy Fix-it Jul 27 '14 at 22:30
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There is no reason to provide accessibility to a supplementary grounding electrode and the code requires it to be at or below surface. The important point of the code is that the supplementary electrode be driven so that it has at least 8' of full contact with the ground. Excavating and backfilling are likely to reduce the effective contact.

  • I've seen concrete pours where a piece of PVC pipe of sufficient diameter was used to create a well exactly for this. Large enough to fit your hand and a tool to tighten the clamp to the ground rod down at dirt level. – Fiasco Labs Jul 27 '14 at 4:36
  • Thanks for the answer! I assume that using a 10' ground rod would likely satisfy the 8' contact requirement. Also, since there is pavement all around the supplementary electrode area for some distance, would the code allow for bonding the two rods by running a wire above ground (i.e., via a PVC conduit along the basement ceiling)? – user339676 Jul 27 '14 at 4:39
  • I was actually considering drilling a large hole and inserting a large-diameter PVC pipe full of soil that would stick above ground several inches so I can keep part of the rod accessible, but still below "dirt level". Would this be a code violation? I might have to access the rod again as we're renovating. – user339676 Jul 27 '14 at 4:44
  • My understanding is flush. My intuition is that there is zero reason to fiddle with it once it is properly installed because the only thing that can happen is that the installation can become less safe. My recommendation is to review the code in your local library. Keep in mind that the purpose is to prevent potentially fatal shocks and that these can occur at any time. It's not like working on a ladder. – ben rudgers Jul 27 '14 at 5:16

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