I am trying to run a bunch of network cables from my network switch in the basement into the attic so that I can disperse them throughout the second floor bedrooms. At the same time, I needed to repair some Romex cables that squirrels bit and chewed through in my attic. I decided to replace the entire span of damaged Romex. I paid to have the attic "squirrel-proofed" with a one way door and their entrance-way was fully sealed so they wont be damaging things anymore hopefully. Also at the same time that of all this is happening, I am deciding to take the opportunity to run two more 14 gauge and two 12 gauge Romex pulls for a planned attic expansion.

Anyway, I am trying to figure out what the best way of routing all of these wires would be. I had to rip out the drywall because the wires were stapled to the frame when the house was renovated in the early 90's so my only option was to cut into the drywall to unstaple them. So I was able to take a good look at what is going on behind the walls. There are a whole host of "alarm", telephone, and COAX wires running DIRECTLY on top of the Romex. This was likely done by the lazy alarm installer technicians AFTER the electricians did there work in the 90's. I am pretty sure that is not to code to have low voltage wires run through the same hole as 110v. I want opinions on the best practices of how I can go about "cleaning" this mess of wires up. I noticed that when we run our portable space heater in the upper floors, the 14 gauge Romex gets luke "warm" which I don't particularly like.

Finally, I wanted to know if it would be okay from a structural standpoint to drill an additional hole through the header joist for the front facade of the house between the first and second floors for the network cables and new Romex runs. Or would it be OK to put in a notch with some nail guards?

Here are some photos of the situation. I would just like to get some professional opinions on the matter. Pictures:

From the basement: Coming from the Basement

Passing over a stud: (this happens due to the fact that the wires run behind a closet on the second floor. I could technically bypass this and go straight up but I'd possibly have to knock down more drywall on the second floor. ) Crossing over a stud

Going up to the second floor: (the network cables just "float" past the header joist and do not go through it at all) Going up to the second floor

At the end of the day, I will have a total of SIX Romex Cables, One for the front two second floor bedrooms, one for the back two bedrooms, one for the front attic renovation room, one for the back attic room, and two 12 gauge for HVAC unit and appliances (in the attic renovation))

  • Personally, I wouldn't run any NM ("Romex") cable smaller than #12. You're just not going to save much money, especially in a small installation like this, and #12 leaves you open to more expansion possibilities later. Dec 18, 2015 at 19:05
  • Also, you should plug those holes with some kind of firestop caulk or foam. Dec 18, 2015 at 19:06

3 Answers 3


Well, your pictures have twigged an occasional issue I run into where I can't see them, (likely not your fault) but flying blind....

From a functional point of view you really don't have to worry about separation. Twisted pair is actually quite good at ignoring noise, and 60 Hz noise is of little note to 100MHz ethernet anyway. You can do it all wrong and it will work, 99% of the time. I don't suggest that you do it all wrong, I do suggest that you don't freak out about it.

From a code (and safety) point of view you should not have low and line voltage going through the same hole, and from a hyper-cautious network standpoint they should be separated by a good 12" when parallel, or cross at 90 degrees if they need to cross. Separation matters a lot more in an industrial environment with noisy devices on the powerlines than in a typical single-family residence.

From a "best practices" point of view, network and power in separate stud bays (when running vertical) or between different sets of joists when running parallel to the joists is certainly a best practice, though not required by code - it maintains separation quite aggressively.

Notches are far worse than "holes in the center third" (top to bottom) of a beam, joist, or header. Holes should not be too close to the ends, even in that center third. I'm not sure there's any need for the cables to go through the header if they can "float by" (remember, I'm flying blind here)

Portable electric heaters are nasty, nasty loads. If you are plugging one into a 15 amp (14 Ga) circuit that, all by itself, with nothing else on, is loading the circuit very near to maximum (if it's a 1500w heater, actually more than is permitted for fixed/hardwired loads that might (as with a heater) be on for more than 3 hours. A warm wire is fully expected under those conditions. A 20 amp (12Ga) circuit would be more appropriate if you are in the habit of using one.

  • Thank you, this was mostly an inquiry into the safety and general code compliance of things. My wife loves using her 1500W Lasko heater in just about every room so your suggestion of #12 and 20A seems appealing. Also, those are 100ft Rosewill CAT7 SSTP cables which are shielded, so I'm not too worried about noise. The header joist section you are looking at is located approx. 3-4 ft from the front left edge of the house's front facade (which is maybe 25-30ft ish wide). Dec 18, 2015 at 5:24
  • If you're talking about Gigabit or faster Ethernet, you're pretty likely to have unhappy results if you do it all wrong... ;-) Dec 18, 2015 at 19:03
  • 3
    @Craig I only run gigabit ethernet. In several places I have long runs parallel to power wires without spacing (old buildings, sometimes there just isn't much choice.) I have switches that report error rates. I don't get errors; so I speak from experience. Are you repeating something you were told or speaking from experience?
    – Ecnerwal
    Dec 18, 2015 at 19:14
  • 3
    If you install the cable properly you shouldn't have any issues. However the NEC requires a 2 in spacing in Article 800.(A)(2) Other Applications. Communications wires and cables shall be separated at least 50 mm (2 in.) from conductors of any electric light, power, Class 1, non–power-limited fire alarm, or medium-power network-powered broadband com-munications circuits
    – ArchonOSX
    Dec 18, 2015 at 21:33
  • @Ecnerwal experience, although ignoring things like minimum bend radius is likely to cause bigger problems (up to and including total failure of the link) than running the Ethernet cable "too close" to 120V wires, and it can also depend on what kind of noisy load is attached to those wires. You said "do it all wrong and it will work 99% of the time." I just think "do it all wrong" is pretty darned inclusive. ;-) However; I do agree that in this case the homeowner is unlikely to encounter any real problems with the Ethernet if it isn't kinked and it's terminated properly. Dec 19, 2015 at 7:44

You have a very good answer from @Ecnerwal, this answer just adds a couple additional considerations. The first: conduit. While you have the walls open, install conduit to the attic. This will give you better protection from interference if you use something metallic, and of course better mechanical protection, and better fire safety. Conduit gives you much more flexibility in the future. You'd have to take a close look at the framing and your plans to determine the exact type, size, and number of conduits.

The second: an electrical subpanel and an ethernet switch in the attic. This may or may not be worthwhile, and you probably already thought of it, just mentioned in case you didn't consider it. If your attic is readily accessible, so you can get to the panel easily, you can run a three wire feed for electrical, and a single cat6 for your ethernet, and do all your future wiring within the attic.


keeping the future in mind adding a 70 amp feeder and panel is a wise idea. A run of four 1 inch emt conduits, and one 2 inch emt conduit between the basement and attic is wise. That's in addition to the feeder conduit. In the 2 inch conduit I advise running a fiber riser paired with media transceivers. It will cost more initially but the ability to expand as technology does is worth it. The 1 inch riser conduits are for the existing wires that were sloppily done to run in.

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