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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?

Ack
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Arcite
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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 06 '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 06 '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 06 '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 06 '20 at 17:50
  • The fire sealant I use in industrial facilities is a putty that never hardens. It works great and with a pull string in place it acts like a cheese cutter and a plug can be pulled out new wire added put the putty back in. I have used this in hospitals and I get the toughest inspections there and it passed. – Ed Beal Apr 06 '20 at 18:04
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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 07 '20 at 19:09
  • I usually only cut 3/8 holes for Romex runs and yes you are correct cutting a large hole doesn’t make sense to me where it’s not needed I run conduit all the time rigid that’s the standard in heavy industrial facilities but in residential I normally only use conduit for the service drop. if exposed and required I use conduit there but for data in a wall if I was feeling the need maybe 1/2” smurf tube (flex plastic conduit normally blue so we call it smurf tube). – Ed Beal Apr 07 '20 at 19:36
  • Not to get too far afield, but the Carlon ENT conduit, aka smurf tube, is what I have, it's just 3/4 rather than 1/2 and the outer diameter is 1.05". The Carlon brochure shows that the outer diameter of the 1/2" conduit is 0.84", so even that would require a 7/8" hole for clearance. – Arcite Apr 07 '20 at 21:43
  • Rim joists also run parallel to the common joists. To my mind the term refers to the joist at the outer edge of any floor system, whereby it's supporting a wall above or perhaps a railing structure (as in a deck). – isherwood Sep 03 '20 at 18:44

1 Answers1

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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

Ack
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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 06 '20 at 04:51
  • 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 06 '20 at 06:59