Pre-drilling studs around new panel

dgeistDecember 12, 2011

I'm installing a new sub-panel in my home in the stud wall between the attached garage and a utility closet. I'm hoping to retain access to the area around the sides of the panel from the closet side for future work. Because that side is unfinished and flush-mounting the panel in the garage will break the fire rating of the wall, the inspector wants me to have a full stud box on all 4 sides of the panel with 1/2" gypsum (minimum) on the back side to meet fire code, which makes perfect sense.

When I do work later, drilling out the studs from inside the panel will be difficult. Can I pre-drill holes in the studs in the framing members (structural rules being followed, etc.) and simply leave the knock-outs in place until I use them? Optionally, I could fill the holes with a fire rated foam or similar until I'm ready to use them.

Any thoughts?


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Ron Natalie

You'll have to talk to your local inspector. I see nothing wrong with it. THere's a fire block product about the consistency of modelling clay that might be the best bet for plugging holes.

    Bookmark   December 12, 2011 at 1:01PM
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"the inspector wants me to have a full stud box on all 4 sides of the panel"

That's about the dumbest thing I have ever heard. I have NEVER seen a panel boxed in on all 4 sides. Sounds like rubbish to me.

    Bookmark   December 12, 2011 at 7:17PM
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The code no doubt requires a fire resistant surface on the garage side of the wall. Our code does. But the surface on the house side of the wall has no such requirement here. If it does not have a stated requirement there, the inspector is just engaging in a flight of fancy. But complying might be easier than fighting with him.

    Bookmark   December 12, 2011 at 9:19PM
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I would think a lot about surface mounting the box on some 1x for nailing cables.

    Bookmark   December 13, 2011 at 11:39AM
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btharmy, perhaps I mis-explained. Since flush-mounting the panel in the garage effectively breaks the firewall between the garage and the unfinished stud walls of the utility closet behind (which is exposed to open airspace above occupied rooms), the panel itself must have a functional firewall behind it, basically saying gypsum behind the panel and having it hard-mounted on all 4 sides around the panel cavity. The use of studs was just an example (albeit probably the easiest one). I could also simply sheet-rock in the entire back side of the wall behind the panel, but then I'd have no access for future work, which is one of things I'm trying to retain.

brickeyee: the surface mount would be a good idea except for my better half has aesthetic veto power on anything going into a room she's going to see on a regular basis. She's also an electrical engineer, so she can pull the spousal trump card on anything conveying current :)


    Bookmark   December 20, 2011 at 4:15PM
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"She's also an electrical engineer,..."

Does she know anything about the NEC?

It is not covered in most four year engineering schools.

    Bookmark   December 20, 2011 at 7:36PM
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Correct, I get to deal with anything AC around the house as her specialty is DC and at lower voltages, but the girl does know her theory and a happy wife is a happy life (since I was talking about asthetics of surface vs. flush) :)

    Bookmark   December 20, 2011 at 8:36PM
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