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I'm in the process of trying to run some CAT6 and speaker wire at various places in my house. One of the things I'd like to do is run speaker wire in the living room to a wall plate behind my sofa, for the surround sound speakers. This is an exterior wall that runs parallel to the joists in the crawlspace below. Thus, it rests directly on an end joist. Running wire through it will require drilling up at an angle through the joist, creating a diagonal hole or what may wind up being a notch.

I've found previous discussions of this issue, such as this one on this very forum,, or this one on another forum, where people say it's OK to do this through a rim joist (aka band joist.) However, I'm given to understand that the term "rim" or "band" joist refers specifically to the joist at the end that is perpendicular to the other joists and which they butt into, whereas the joists at the end that are parallel to the other joists are called "end" joists. Now, the logic by which this is said to be OK is that the rim joist is continuously supported by the foundation wall, so the segment you'd be drilling into, between studs, is not really bearing any weight or tension. But in my case, the end joist I want to drill through is also continuously supported by the foundation wall, so I don't see why the same logic wouldn't apply.

Furthermore, the builder has already done this, having drilled a diagonal hole here and there at points in this joist to run romex for power outlets along the exterior wall. I would just like to drill a somewhat larger hole (1 1/8") to accommodate ENT conduit. Can anyone comment on whether this would be OK?

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  • 1-1/8 hole how many cable and speaker wires are you running? I would run them under the house or in the attic and forget the conduit. – Ed Beal Apr 6 '20 at 13:35
  • Just trying to future proof it and be able to fix it more easily if something doesn't work. One 4-conductor speaker wire plus one coax for the subwoofer. It's 3/4 inch inner diameter conduit, but 1 1/8 is the smallest drill bit size that's larger than the outer diameter. – Arcite Apr 6 '20 at 16:30
  • I would put a pull string in and probably go inside above or below not outside that would require conduit. Still future expansion available at 1/4 the cost. – Ed Beal Apr 6 '20 at 17:11
  • I'm not planning on going outside, just running the conduit through the crawl space. The problem is that by code all holes in plates/studs have to be sealed with fire blocking sealant so once I've done that, without conduit, it wouldn't be easy to simply pull something additional through. – Arcite Apr 6 '20 at 17:50
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    I understand you don't think there's a good reason to run conduit, but just to be clear, is it because there's a structural problem with a 1 1/8" hole? Because I already have the conduit, so cost doesn't factor in, and I like the idea of using it, so unless doing so would actually be harmful, I would like to use it. – Arcite Apr 7 '20 at 19:09
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It would be ok to notch or drill the end of the joist on a supporting member. Keep it in the middle or top section, not the bottom where it is bearing.

Rim joists DO bear load in many cases, however, drilling holes will not significantly downgrade the ability to carry that load and therefore it's ok. HOWEVER, rim joists on the second level or higher can be part of the lateral system and at most remove 1/3 of the depth and in the middle of the rim joist

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  • None of your pictures cover the case of a joist that parallel to the exterior wall and supported by the foundation wall as asked about in the question. -1 until you can directly address the question. In addition unless you personally drew these pictures you are required by site rules to provide attribution as to where they came from. – Michael Karas Apr 6 '20 at 4:51
  • Thank you for the information. I've removed the picture because I don't feel like dealing with the credit issue. This detail can be found in both the IBC and WFCM and other codes, text books and is a standard detail on most structural plans. While it did not show the exact detail in question it is the generic information about where it is acceptable to drill or notch wood members and that does relate to this question. It does not matter if the joist under the exterior wall and on top of the foundation is parallel or perpendicular, it is a rim joist and everything I've stated is accurate. – Ack Apr 6 '20 at 6:59

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