I have a metal I-beam in my basement that supports my floor joists.

I am running new electric, and I want to use it as a sort of running board - I know I can't string certain gauges perpendicular to my floor joists without drilling through them, but this beam - running perpendicular to the joists - seems perfect.

Is it acceptable to install wires within the cavity of this I-beam? I'm eventually going to be wrapping this beam in drywall when I finish the basement.

If acceptable, how should I affix NM securely inside the cavity? Should I attach (glue, etc) a board inside the cavity so I can use staples? Should I use some plastic holder I can attach (glue, magnet, etc)?


enter image description here

  • This can be done there are many options you can take, search RSJ cable clips. Sep 4, 2023 at 4:58
  • Is there any reason you can't just frame it out right now, even if you don't actually put up the drywall for a while?
    – Huesmann
    Sep 4, 2023 at 12:24

2 Answers 2


There are two issues:

  • Protection from damage

This is actually not such a problem here. It is a big issue with walls, but with ceilings normally not a concern. That being said, if you use conduit then it will provide protection and keep the wires out of the way.

  • Securing the Wires

There are a bunch of ways to do this. A lot depends on wires vs. cables.

For individual wires, you secure the conduit to the beam and the wires go inside the conduit. If you use conduit then you actually can have some long spans. According to this page the allowable distance is at least 3 feet for non-metallic conduit (PVC) and at least 10 feet for rigid metallic conduit. Which means if you use RMC then you spend more on the conduit but it basically supports itself across the room!

If you are using cables (NM cable, a.k.a., Romex) then you need to secure them within 12" of junction boxes and at least every 4-1/2 feet. If you are running the cable along wood then you normally use staples. On metal you need some sort of clamp, such as a beam clamp and attach a hanger to the clamp which then holds the cables.

  • I'm planning on using NM cable, and running the cable inside the cavity of the beam (where my finger is in the image) - and potentially quite a few of them. Does it make sense to install a running board inside the cavity of the beam?
    – user112697
    Sep 4, 2023 at 18:52
  • 1
    You only need to secure the cables every 4.5 feet. I don't know how long this beam is, but for example if it is 16' then you just need to attach the cables at 5 spots (e.g., 0, 4, 8, 12, 16), so instead of a running board going the whole distance, you could put in a small piece (e.g., chop up a 2x4) at each of those spots and use staples to attach the cables to the boards. Sep 4, 2023 at 18:58
  • That makes sense, thanks for the clarification! That's probably what I'll do.
    – user112697
    Sep 4, 2023 at 20:38

You can run the wiring in PVC or EMT conduit, and attach the conduit to the beam using "beam clamps".

If this is a basement and not a living space, or if you will box it in when it becomes a living space, you don't need conduit.

You can run the conduit or cable as shown in the picture here, or in that corner where you plan it. Either way, conduit/boxing or not depends on the use of the room.

enter image description here

Ref: https://www.youtube.com/watch?app=desktop&v=g0O6M-HWsKk


enter image description here

  • Do I need to use conduit? This is currently an unfinished basement but will eventually be finished. The pictures you attached show a clamp below or jutting out to the side; I'm hoping to run the cables within the cavity. Is that permitted?
    – user112697
    Sep 4, 2023 at 18:53
  • @user112697 see the answer about when conduit is needed. As for where to run the cables, I updated the answer.
    – P2000
    Sep 5, 2023 at 3:18

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