What are the NEC rules for holes in a wooden wall top plate? Specifically, how far apart do the holes need to be and what is the max diameter of a hole? In NEC 300-4 I found "...holes shall be bored so that the edge of the hole is not less than 1 1/4 in. (31.8 mm) from the nearest edge of the wood member." Is this all there is regarding this topic? Thanks.

  • 3
    There is probably nothing else in the NEC about this, but other codes like general building codes, may have more to say about it. You may want to expand your question to include those. Feb 17 at 19:19
  • 2
    Yes, the NEC doesn't concern itself with framing. The dimension you cited has to do with protecting the wiring.
    – isherwood
    Feb 17 at 19:26
  • The NEC only requires they be spaced 1-1/4 back or a nail plate is required, some quote 1” on center but reality is if there is a wood webbing between the holes it is an individual hole. Any holes not directly above the panel require holes in the studs. I would rather obliterate the plate area like a 3” vent stack does than having more holes in studs.
    – Ed Beal
    Feb 17 at 19:39

Don't make it larger than half the top plate's width

Since the size of holes in a top plate is a structural concern, not an electrical concern, you need to be looking in the IRC (or other building code) for these details, not the NEC. In particular, IRC R602.6.1 states that a metal top plate tie strap is needed for a notch or hole in a load-bearing top plate that extends through over half of the top plate's width; unless you're running fat conduit or SE cable, you won't come close to this, though.

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