Minimum wall thickness for Romex?

JoeNorm

Senior Member
Location
WA
Does the NEC specify a minimum wall thickness to run NM cable through? For example, can I run it along a 2x2 (1.5"x1.5") stud with drywall on both sides.
I think the answer is yes but I'd like to be sure.
Thanks
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I would use something like Colorado Jims to distance the Nm a bit. They're also much easier than stapling.

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infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Does the NEC specify a minimum wall thickness to run NM cable through? For example, can I run it along a 2x2 (1.5"x1.5") stud with drywall on both sides.
I think the answer is yes but I'd like to be sure.
Thanks
The answer is no unless it's secured to the stud at least 1.25" away from the edge of the stud.
 

JoeNorm

Senior Member
Location
WA
The answer is no unless it's secured to the stud at least 1.25" away from the edge of the stud.
So it cannot be stapled to a 2x2 like I proposed? Surprised to hear but glad I asked. How is this typically accomplished besides using the device Larry posted?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
So it cannot be stapled to a 2x2 like I proposed? Surprised to hear but glad I asked. How is this typically accomplished besides using the device Larry posted?
You actually could staple it to the 2X2 but it would require protection. Better method is to use the Colorodo Jim cable support that Larry posted and keep it 1.25" away from the stud edge.
 

Carultch

Senior Member
Location
Massachusetts
The answer is no unless it's secured to the stud at least 1.25" away from the edge of the stud.
On a 2x2 stud, the 1.25" from both edges will overlap. You also usually want to aim for the center of a stud when drilling, because the outermost fibers are the most important to its structural performance (a factor not considered in the intent of the 1.25" rule, but that benefits from it). A standard 2x4 stud has the middle inch available for routing wires and complying with this rule. Any stud that is shallower than 3" has no space available to comply with this rule, since it would apply for both sides.

Given 2x2 studs, you would have to send the wire through the middle half inch, and protect every single one of them with a metal plate. Also considering that you are now removing 1/3 of the material at that cross section, you may want to check with the team who specified this kind of stud whether it is acceptable to do this. It will impact the strength of these studs to a much greater extent than it would do for a standard stud.
 

kwired

Electron manager
Location
NE Nebraska
On a 2x2 stud, the 1.25" from both edges will overlap. You also usually want to aim for the center of a stud when drilling, because the outermost fibers are the most important to its structural performance (a factor not considered in the intent of the 1.25" rule, but that benefits from it). A standard 2x4 stud has the middle inch available for routing wires and complying with this rule. Any stud that is shallower than 3" has no space available to comply with this rule, since it would apply for both sides.

Given 2x2 studs, you would have to send the wire through the middle half inch, and protect every single one of them with a metal plate. Also considering that you are now removing 1/3 of the material at that cross section, you may want to check with the team who specified this kind of stud whether it is acceptable to do this. It will impact the strength of these studs to a much greater extent than it would do for a standard stud.
If the wall is framed with 2x2's there is probably no real structural value to that wall, it is just a thin partition.
 

480sparky

Senior Member
Location
Iowegia
If it's 2x2s used to frame an exterior basement wall (next to foundation), keep everything as far back as possible. The 'other' side won't be finished.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Given 2x2 studs, you would have to send the wire through the middle half inch, and protect every single one of them with a metal plate. Also considering that you are now removing 1/3 of the material at that cross section, you may want to check with the team who specified this kind of stud whether it is acceptable to do this. It will impact the strength of these studs to a much greater extent than it would do for a standard stud.
I don't think that the OP is asking about going through the studs he mentioned stapling to the side of the 2X2.
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
Interesting issue, for attachment parallel to or drilled and passed thru a stud you must keep wire back 1.25". But you are allowed on old work to run within finished walls to fish a NM wire in the void, and it's not secured to a stud. How is it a minimum setback not issue under this old work condition but it is under a new installation condition?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
How is it a minimum setback not issue under this old work condition but it is under a new installation condition?
Possibly because the drywall screws or nails have already been driven, and a fished cable can move out of the way of any new ones.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Interesting issue, for attachment parallel to or drilled and passed thru a stud you must keep wire back 1.25". But you are allowed on old work to run within finished walls to fish a NM wire in the void, and it's not secured to a stud. How is it a minimum setback not issue under this old work condition but it is under a new installation condition?
Someone mentioned the stapling is only there for the sheetrock installation so the installer doesn’t hit the wire with the nails or screws.
Hopefully they aren’t using 2-1/2 screws on new work..
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Hopefully they aren’t using 2-1/2 screws on new work..
Laminating a ceiling with a new drywall layer, such as when covering a textured one, often requires much longer screws, so ceiling wiring can be at risk. Fortunately, joists are deeper than studs, but I have seen holes rather near the bottoms.
 

kwired

Electron manager
Location
NE Nebraska
Laminating a ceiling with a new drywall layer, such as when covering a textured one, often requires much longer screws, so ceiling wiring can be at risk. Fortunately, joists are deeper than studs, but I have seen holes rather near the bottoms.
Yes longer screws needed, not so much because you need deeper penetration in the framing member though, you need to penetrate the first layer of drywall before reaching the framing member.
 

JoeNorm

Senior Member
Location
WA
To clarify, this was a theoretical when I asked about drywall on either side. I said that because I didn't want to take the time to explain the actual scenario. Here goes:

I have a situation where the builder has attached plywood to the underside of roof trusses in order to create a ceiling with a tight air barrier. He will then fur down with 2x2's to attach his drywall lid. He wants to use the small space in between as a chase for wires. 2x2 is ideal because he has standard double top plate so doesn't want to drop too far.

It's a tight attic above, so I suppose you could say the wires are safe on the side of things anyway?

this is where this question originated. Thanks for the replies
 
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