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diverdaveman 07-09-2007 05:12 PM

NEC code on rewiring?
Iím going to rewire a house I just purchased that was built in 1948. Iíve already paid an electrician to pull and update my service. The rewire will not be hard because the old plaster walls needed to come out so it looks like new construction except the exterior walls. Iíve attempted to do some research on what NEC code says about rewiring with no luck. I do have a question if someone can help me out. Many thanks in advance.

When running the wire horizontal through the studs, a metal plate must cover where the wire run is so that a nail canít penetrate. This is no problem on an interior wall where the metal plate can be mounted on both sides of the studs, but what about the exterior walls? What will keep a nail from being driven into the wire from the outside?


johnny331 07-09-2007 06:01 PM

There are "rules" on the penetration depth of nails used on the exterior, just for that reason,

what those rules are, i have no clue :)
I'm just waiting until all the exterior is done!

Stubbie 07-09-2007 07:24 PM

No way to go over all the requirements but if this is a total rewire then it will basically need to be up to the latest NEC code that your local juristiction recognizes.....probably 2002 or 2005. You need your permits and inspection schedule. Your local codes department should have a guide to help you out.

As for the horizontal runs through wooden studs you don't need a nail plate at all if the wire is not closer than 1 1/4" from the face of the stud. So a center drilled 5/8" hole in the stud will keep you from having to use nail plates with a tad to spare.

Below is a guide for requirements to meet 2005 code, this is only for your reference to get you started thinking right. Get yourself a book on residential wiring and bone up. Knowing the requirements is not necessarily knowing how to wire them.

Dont forget your smoke detector rules. Copied section IRC.....

Smoke detectors are required in each sleeping room, outside of each sleeping room, and in each additional story including basements and cellars but not crawl spaces. Where more than one smoke detector is installed to meet these requirements, all smoke detectors within the dwelling unit require an interlock or interconnection in a suitable manner that upon activation of one, all alarms will be activate

Make sure you can do this without being a licensed electrician. Cover your bases (rearend). The liability doing this without inspection would be unacceptable.


and this may help but is very detailed for new constuction

diverdaveman 07-09-2007 10:39 PM

Thanks Stubbie for your comments. I just picked up my permit today for plumbing and electrical, so I'm doing things the legal way and right way. Thanks for the concern. Also, great thougth to find out if my area uses 2002 or 2005. I just assumed everybody was using 2005.

I've been looking for books - do you have any recommendations?

Just a little more info. Right now the house is wired with all the recepticles wiring coming up from the crawl space and the lighting is in the attic. I thought about using the same paths, but didn't know if the NEC would allow that. Any thoughts?


Stubbie 07-10-2007 01:53 AM


I've been looking for books - do you have any recommendations?

You can find it locally for less. Try your local bookstore or trades bookstore.


Just a little more info. Right now the house is wired with all the recepticles wiring coming up from the crawl space and the lighting is in the attic. I thought about using the same paths, but didn't know if the NEC would allow that. Any thoughts?
You can but I wouldn't. Since you are removing the wall covering to basically bare studs and wall cavities I would run my cables through bored holes in the wall studs and make my junctions in switch boxes and receptacles boxes. I would stay out of the crawl space except of course for equipment that might be down there. Run power to your switches first then to the lights. Stay away from switch loops where power goes to the light first then to the switch. This way you always have a neutral wire in the switch box. Make good use of 3 way switches they are easy and are great conveniences. You dont have to nail all your boxes to studs, if you want a bit better location then get a spanner box that allows you to slide the box on a rail to where you want it. Then the rail nails to the studs. For kitchen walls or others where tile is being installed and your not sure how far out to set the boxes use adjustable blue boxes by carlon. These allow you to set flush then when the wall is finished you use a screwdriver to adjust the box out to be flush to the finished wall. Use big volume boxes, stay away from handy boxes or switch boxes. Be sure to use big volume boxes where ever you are going to have gfci receptacles. These are bulky and take up a lot of room. Use good grades of switches and receptacles the cheapies are junk. I like pass and seymour tradesmen. these are the ones that have the metal yoke wrapped around the device. Don't use backstabs on switches or receptacles use the screws and pigtails or backwire type receptacles. When you pull your nm-b cables don't take the spool and unwind it in spirals take it off the spool like a reel other wise it will be a twisted mess.
Watch your loads don't get too much on your breakers. AC, microwave over range, range, dishwasher are seperate individual branch circuits. Know where your going to have to gfci and afci. Get up to speed on your bathroom, bedroom, kitchen and laundry room code requirements as to gfci,afci , smokes, and the 20 amp branch circuit rating requirements in some of those rooms. Example... the kitchen minimum is two 20 amp branch circuits and they both have to show up on the countertop receptacles.

Cauldwells book will tell you all the requirements and how to run the cables and how to fasten them. Such as only two cables under one staple and within 12 inches of a box etc....

Well I could go on and on. Maybe others will add.

Good Luck


HouseHelper 07-10-2007 07:23 AM

Another excellent book to recommend: Electrical Wiring: Residential by R. Mullin

To add to what Stubbie said: Map out your circuits, drawings and colored pencils are a great help, as is marking on the stud next to the box. Use 14ga for your lighting and 12ga for your receptacles. Double check that your "home runs" are done before closing the walls up. Add more receptacles than the minimum required.

RippySkippy 07-10-2007 07:33 AM

Stubbie, you gave the best single description I've read in along time. I wish I'd put in the adjustable boxes in the kitchen...oh well, next time.

Could you explain this a bit further?

Originally Posted by Stubbie (Post 52335)
...Stay away from switch loops where power goes to the light first then to the switch. This way you always have a neutral wire in the switch box. Stubbie

Why do you recommend it? I try do it as you say....but on occasion, I don't depending on the situation, so far I've not run into a problem.

diverdaveman 07-10-2007 07:52 AM

Once again, thanks Stubbie!!!! I agree with RippySkippy - that description was great. I'll have some books by the end of the week.

Thanks again...

Stubbie 07-10-2007 11:40 AM

Two things it keeps your wiring in the walls (in dave's situation) and not run thru the attic. Having a neutral in the box lets you grab power in an easily accessible location for further additions or last minute changes. Many devices that install in place of a normal switch require neutrals. It simply gives you more options without rewiring. I would also add that anywhere where you think you might add a ceiling fan someday I would go ahead and wire it up with 14/3 or 12/3 put a double gang box in and cap off the red wire, install a single gang cover and single pole switch. Then if you ever add that ceiling fan just install a double gang cover and add your second switch for the light and connect the switched leg to the red wire. Same thing in baths you never know what your going to change as for ceiling installed fans and lights. If you wire for the future it makes it a pretty simple deal and not much extra cost for one extra wire. Your undoubtly going to need a roll of 3 conductor cable so might as well make good use of it instead of throwing a hundred feet of it up on the self in the garage.

Househelpers advice about mapping the circuits is invaluable especially after you close things up . Now you can reference what wires go where and it may even be required for inspection.


RippySkippy 07-10-2007 12:03 PM

All right Stubbie I'm with ya.

In addition to the sketching, digital pictures are especially helpful after the drywall goes up.

Stubbie 07-10-2007 12:43 PM

Digital Pictures....Hmmmm...that is a great idea!!


diverdaveman 07-10-2007 07:37 PM

Okay, I started pulling out the old wire today. Everything went great. I did notice something today that could hinder my rewire job. The house was built in 1948 and in the corner of every wall (interior and exterior) is 4x4 studs. The 4x4 studs are butted up against each other. This will hinder me from running the wire around the perimeter of the room through the studs.

The only thing I can come up with is to drill either a 1" or bigger hole in each then fish it through. If I do this there will be tight curve in the wire.

Has anyone ran into this before or have any other suggestions? I guess if I can't run it through the corners, all of the wire will be dropped down from the attic.

Many thanks in advance,

HouseHelper 07-10-2007 08:12 PM

You can drill a hole as you propose or cut/chisel a channel in the surface to route the wires through. In either case you will need to use nail plates to protect the wire. Just don't make the radius of the curve too tight. Or you can go up (through the top plate) and over to get around the corners.

diverdaveman 07-10-2007 08:22 PM

Thanks HouseHelper for the reply-

Is there a code or a "suggested" code on how tight the curve/radius should be in the corners?


Stubbie 07-10-2007 11:55 PM

Yes, but it usually is never an issue, but for your reference NEC Art. 334.24 states as follows


Bends in types NM, NMC and NMS cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend during or after installation shall not be less than 5 times the diameter of the cable.
Well in general your never going to violate that code bending a 12/2G , 14/2G around a 90 degree stud wall corner. How you would ever enforce that article I couldn't tell you cause you can't measure the bend. Just center bore the posts and fish the wire through. Use a short piece of #12 slip a 1/4 by 20 nut with a string tied to it on the #12 wire stick it through one hole, stick your magnetic tool retriever thru the other hole and catch the nut pull your #12 out ....the rest you can figure out I'm sure. Take your needles and grab the romex about 1/2" behind the end and bend the cable back on itself to make a rounded end, tie on the string and well you get the picture. This will be a hard pull thru that corner so you may want get some wire lube to make it easier. HD or lowes for about 5 bucks. Do not use grease or anything that may deteriorate the jacket of the cable.

In your case you have no void but this is the general idea. Use auger bits to drill your studs. Don't use spade bits.

Dont' drill great big holes in the studs or 4x4's. In your case it looks like you have true 4" studs so measure in 1 1/4" from the inside face and 1 1/4" from the outside face your hole cannot be any bigger than the distance between the marks, if center drilled to avoid nail plates. Or another way to look at it is for load bearing and non-load bearing walls holes cannot be bigger than 40% of the stud diameter or approx. 1 1/2" in your case center drilled. Doubled studs can be drilled at 60% of diameter.

This is a typical example of a guide available from codes department


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