Wiring between strapping

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jzadroga

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In my area a lot of electrical contractors wire between strapping when roughing in a residence. For those of you that don?t know what this is let me explain:

In my area when a house is being built, they often use 1?x3? strips of wood nailed to the bottom of the ceiling joists. These strips are about 16? on center and at right angle to the ceiling joists. This is done, from what I understand, to allow the ceiling to be leveled before the blue board and skim coat of plaster are applied.

This creates a 3/4? channel below the ceiling joists that some electricians use as a chase during the rough to run their wires and avoid the time necessary for drilling. I personally do not like this method as I feel it is not safe. If after the home is finished someone adds a recess light or anything they stand a good chance of cutting that wire or wires because they are right behind the blue board. Some building inspectors so I?m told will even fail the structure if the electrician drilled the ceiling joists instead of wiring between strapping. I know that ceiling joists as well as all wood members are allowed to be drilled according to the defined specifications of the building code in my area.

Essentially my point is this: does NEC allow this and what are your comments about this practice?
 
Re: Wiring between strapping

Definately not, 300.4(D). An 1-1/4" space must be maintained. Those joists have to be drilled unless it is practical to install nail plates wherever this occurs.
 
Re: Wiring between strapping

If the nail strips are 16" on center and the cable is stapled somewhere in the middle, 300.4 (D) wouldn't apply, and this distance would also take 300.4 (E) out of the argument.

How would those who are wiring C.B. type homes with furring strips on exterior walls accomplish this without buying stock in kick plate companies?

Roger
 
Re: Wiring between strapping

I have been wiring houses using the space between the strapping and joist's and it has never once been an issue on an inspection or otherwise.Drilling holes thru joist or micro beams can become a problem but if you check with the biulder or manufactures specs first before drilling u can head the problems off before it arises..
Kelley
 
Re: Wiring between strapping

In my area this is very common, I would hate to rough a dwelling without the strapping. It is all in what we accustomed to. I have heard that this is a northeast thing. As far as cutting a hole in the ceiling, we usually open a small test hole and probe with a snake. Might use more staples, but a hole lot less drilling!
 
Re: Wiring between strapping

In my state -Mass.- the Mass. amendments to the NEC delete 300.4 (D). This permits this wiring method.
 
Re: Wiring between strapping

This is another example of how different things are in different areas of the country. I'd never seen this "strapping" used in construction until I saw it on This Old House. It's not used in the Southeast that I'm aware of.

You Northeastern guys would be in for a lot of hole-drilling down here.
;)
Russell
 
Re: Wiring between strapping

I forgot to mention that we are able to fish in wiring in these 3/4" spaces perpendicular to the joists. This saves a lot of plaster repair (or surface raceway).
 
Re: Wiring between strapping

Last time I looked N.Y. was considered a northeastern state -We currently apply the N.Y.STATE RESIDENTIAL CODE Which uses N.E.C."99 as its reference with certain ammenedments.1999 300-4 [d]@300-4[e] "cables and raceways parallel to framing members"@"cables and raceways installed in shallow grooves" .You say you get a 3/4" space -As I read it, you a minimum of 1@1/4" clearance is required--if I came across the method of wiring that you're talking of during a rough insp. I'd have a good laugh-then I'd tell the contractor to get a lot of nail-on plates or go back and start drilling.
At that point I'd say the drilling wasn't so hard after all.
 
Re: Wiring between strapping

mthead as long as the wiring is stapled to the joists and a 1 1?/4" distance is maintained from the furring why would it be necessary to drill the
joists ???? 1000`s and 1000`s of block homes are wired in a similar manner except the chase is on the walls.The 1 1?/4" is maintained using stackers/stand offs. Since most 2 story homes here use floor trusses drilling thru them isn`t an issue,but when joists are used break out the 90` hole hog.....
 
Re: Wiring between strapping

Mthead, please explain how you interpret 300.4(D)&(E) in a little more detail so we can laugh too.

Allen is on the money.

Roger
 
Re: Wiring between strapping

I guess it all depends on where you live and the trade practices used. In my part of the south I don't see any new residental construction using plaster, mostly it is wood framing on a block foundation with sheetrock directly attached to the wood, all holes at least 1 1/4" off the face or covered with a nail plate. I intend to ask the AHJ about this the next time I see him (although it'll be a moot point for me).
steve
 
Re: Wiring between strapping

IMO the intent of the 1-1/4" requirement is to lessen the chance of nails or screws penetrating or otherwise damaging wiring. Nails or screws can be driven anywhere in the wall so what makes you think that a cable in the middle of a bay away from the strapping or stud is any more immune? After the wall or ceiling is finished can you see the studs or strapping so that you know where they are?

I always try to keep wiring ANYWHERE in the wall at least 1-1/4" from the back of the sheetrock.

Just the other day I was installing a backboard on a sheetrock wall that had been hung on a block wall with 1X furring. I'm putting my screws in hoping to find the furring and I look down and see a receptacle. Guess where the NM was run.
 
Re: Wiring between strapping

Hbiss, a real or hypothetical instance doesn't change the letter of the code, and there is no specific prohibition of running NM less than 1.25" from the wall board if we stay away from 300.4 (D)&(E), which this installation method does.

As far as a nail being driven in the center of a stud or strapping cavity, what about someone driving a 16 penny nail where you have maintained the 1.25" clearance? Should the NEC go ahead and make metal covering mandatory for all NM wiring? ;)


Roger
 
Re: Wiring between strapping

I know Ryan will love this. :D

300.4(D)Cables and Raceways Parallel to Framing Members. 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, 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 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.

Exception No. 1: Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.
Click to expand...
Massachusetts Electrical Code Amendments
300.4(D) Delete this subsection.
Click to expand...
This does not change the need of 1 1/4" space or nail plates when passing through bored holes or notches etc. as required by 300.4(A).
 
Re: Wiring between strapping

Personally, I am surprised that the powers that be in MA are willing to delete that subsection and expose themselves to any resulting liability. They have made a conscious decision to delete one of the sections that makes perfect sense.

That settles it: The MA AHJ is certifiably insane :)
 
Re: Wiring between strapping

All the houses here in Ma are built and wired in this way. It works perfectly fine and always has.
 
Re: Wiring between strapping

Wayne you have no point of reference to judge whether or not this section is needed.

You think or are assuming it is needed.

I have been doing wiring 20 years here in MA and I am sure Scott has been doing it a while too.

In that time I have never heard of any problems with this.

I am not sure what you mean by liability, this is not like a local inspector changed the code to suit himself.

This is the people who make the MEC, it was never law here so I find it difficult to believe you could sue them because it is the code in other states.

What is your worst case scenario with this section deleted? :)

Bob
 
Re: Wiring between strapping

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