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Saw a picture of an example of code NEC 300.4 (D) where a furring strip was used and a wire was run parallel to the furring strip. Per the code, the wire was 1 1/4" away from the nearest edge of the furring strip.

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This doesn't make sense since the wire has the same chance of getting hit with a nail if the wire was only 1/2" from the furring strip. I realize that this originated from the fact that a hole in a stud has to be 1 1/4" away from the top facing edge of a stud to keep drywall screws from hitting the wire.

But according to this code a wire can be just under the sheetrock as long as it is 1 1/4 " away from the furring strip. I don't understand the logic. Can you please clear up my confusion?

National Electrical Code 2011

ARTICLE 300 Wiring Methods

300.4 Protection Against Physical Damage. Where subject to physical damage, conductors, raceways, and cables shall be protected.

(D) Cables and Raceways Parallel to Framing Members and Furring Strips. In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed parallel to framing members, such as joists, rafters, or studs, or is installed parallel to furring strips, the cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 32 mm (11⁄4 in.) from the nearest edge of the framing member or furring strips where nails or screws are likely to penetrate. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at least 1.6 mm (1⁄16 in.) thick.

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BobJax
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  • Please don't make radical changes to your questions like that, especially after someone has gone to the trouble of answering the original version. Ask a new question instead. – Niall C. Jul 15 '13 at 21:25

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I’m not a NEC attorney nor did I stay in that fancy motel last night but one of the “intents” of “the rules” is to reduce the number of material casualties suffered during construction. A sheetrock craftsman won’t use 16-penny nails to mount sheetrock and is highly unlikely to miss the studs or furring strip with a standard drywall nail or screw, hence the 1 1/4” (and metal plates) rules. Mr. Homeowner, while installing a shelving unit for knickknacks might use a 16-penny nail but I’m confident wiring a house with EMT would turn expensive in a hurry.

JoeFromOzarks
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  • Ouch. Changing your question makes my answer look like I've been hittin' the bottle. (grin) Where did you see that 14awg rule and why would 14awg differ from 12awg? The intent is to prevent standard mounting devices (nails and screws) from breaching the insulation, 1 1/4" deemed a safe distance under "normal" or "typical" installations. – JoeFromOzarks Jul 15 '13 at 21:25
  • @JoeFromOzarks Changing the question like that is considered bad form on this site; I've rolled it back and asked the OP to open a new question. – Niall C. Jul 15 '13 at 21:30
  • Sorry, Niall. Thanks for rolling it back. @JoeFromOzarks Thanks for your reply. I used 14 AWG; should apply to other common wire. – BobJax Jul 15 '13 at 22:31
  • Seems like the solution is to state that if wiring is placed where furring strips are used, the furring strip must be thick enough that wiring can be placed under the furring strip (attached to the wall) and be 1 1/4" from the top edge of the wood. When wiring is parallel to the furring strip, the furring strip must thick enough so that the wiring can be attached 1 1/4" from the top facing edge of the wood. Basically 3/4" thick furring strips would have to be doubled. When asked how the illustrator of the picture came up with his interpretation, there was no answer (that I could find). – BobJax Jul 17 '13 at 13:14
  • If you’re taking the exam, all the information you need is in the text and pictures. For an apartment where risk is slight, you can follow the NEC and probably be fine, forever. However, building a wall for a fellow’s machine shop in his personal garage, I’d be recommending EMT for ensured (additional) protection. :) – JoeFromOzarks Jul 17 '13 at 13:35
  • I am doing EMT, as well, – BobJax Jul 17 '13 at 14:30
  • Aluminum MC cable (with wire) is pretty handy too, especially for those times when you know you won't be fishing new/different cables in the pipe! :) – JoeFromOzarks Jul 17 '13 at 15:38
  • If Aluminum MC Cable is used, do the inspectors consider the wire protected versus EMT. It will be run behind "hand-made crown molding" during a total house rewire (in some difficult rooms). Don't think of conventional crown; think a 1" x 4" board nailed to two furring strips and crown trim added. I do the wood work. I could technically mount the crown on two furring strips and run romex between the furring strips (1 1/4" from each fs) and I would meet that code. But want more protection. – BobJax Jul 18 '13 at 12:59
  • I called a 30-year inspector friend and asked him. He said, in so many words, that using MC or EMT to protect wiring doesn't mean mechanical methods of mounting the crown could pass inspection if the mounting put the wiring (protected or not) at risk. Double talk, I know. (grin) In other words, the inspector might pass the wiring but fail the carpentry. – JoeFromOzarks Jul 18 '13 at 15:58
  • Thanks for checking! Had to think about that one. :-) I won't put the EMT at risk. Even if I accidentally missed every furring strip I was aiming at and hit the EMT repeatedly, it won't hurt the EMT because I use 23 gauge micro pins. When people put up regular crown they may use 18 or 15 gauge or bigger. I assembly my crown from thinner pieces of wood and build it up. One of my wife's favorite crowns, I made from junk furring strips and junk wood strips I bought off eBay. I am bringing the local inspector a drawing or a mock-up. If he doesn't approve I will have to cut the sheetrock. – BobJax Jul 18 '13 at 21:38
  • Your project sounds interesting, post progression pictures if you get a chance, and if it's allowed. :) – JoeFromOzarks Jul 19 '13 at 00:34