Help With Old Attic Wiring - What to do with wiring previously run under attic joists.


Hey all,

Long time lurker, first time poster.

My wife and I purchased our first home back in April, and I'm working on converting our attic space into usable storage. As part of this, I need to redo the rats nest that is the electrical wiring in this space and bring it up to code for an attic space with permanent access. This mainly consists of re-organizing the wiring that's there, running the wiring to NEC code, splicing in a few junction boxes to code, etc.

One of the things that I have not found a straight answer on is what to do with wiring that runs on the bottom side of the joists. I have found 2 of these runs so far in the attic. They run from a junction box in the wall of one room, up into the attic space, under 1 or 2 joists (between the plaster/lath ceiling and joist, and perpendicular to the direction of the joists), and back down into the wall to a junction box in the wall of an adjoining room. It's an unbroken run of wire from one room to the next. Is it OK to leave the wiring like this under the joists, or would I have to re-run this to code (on the tops of joists w/ substantial protection strips running perpendicular to the joists)? If so, this would consist of adding some junction boxes to lengthen the wire.

The internets have not given me a straight answer so far, and neither has the NEC from what I've briefly read through.

Thanks for the help fellow DIYers!

wylekoodard 05/26/2019

Thanks for the advice.

  • I actually just installed a light fixture before you sent this response. I put it in right near where I'm adding an access ladder. Glad I'm ahead of the curve. As a side note, I bought some motion sensing LED bulbs for an under porch area and will be installing these in the attic as well so it will immediately light up once I open the access ladder. I highly recommend them and they can be found here:
  • Not sure I'll need an outlet for the foreseeable future, but that should be something that's easy to add in.
  • Thankfully, I don't have any plans for low voltage stuff, nor do I have any ducts or recessed lights in the floor below.
  • Insulation is going to be going in before I do a final install of the floor boards. I live in MA so the utilities subsidize the cost of blowing in insulation by 75% which is quite nice. Plus I only have about 2in of standing insulation up in the attic currently

I will add, there were two other runs of cables that went under the joists, but these were FMC. I'm less worried about these since they're protected in the conduit vs. being exposed romex like the other wires were. Think this would be a problem?