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aggie_laser · Nov 25, 2007, 05:16 PM

Hi - new to the site, thanks for the help.

It seems that if the wires need to be a minimum of 1-1/4" the edge of a stud, then shouldn't the backs of switch and outlet boxes be as well?

On an interior 2x4 wall, even the smaller 18cu inch boxes encroach into the 1 -1/4" setback required for sheetrock screws. I've looked through some of the NEC books and haven't found a topic that would address this item. With these plastic new-work boxes, it seems like it would be very easy to miss the stud and put a screw into the back of the box, or into the romex coming out of the boxes. On an interior wall, both the back of the box and the wires are very close to the sheetrock.

donf · Nov 25, 2007, 08:18 PM

Please think about what you are saying. The drywall screws are mounted on the stud after the the electrical rough in is complete. The gang and utility boxes are installed prior to the drywall going up.

Normally, you set the boxes so that the front edge of the box will be flush with the front face of the drywall. So, I'm not sure I understand your question.

labman · Nov 25, 2007, 10:11 PM

I never though about that, but it sounds like a good point. I just checked. My 1970 house is wired up mostly with molded phenolic boxes. I measured, it is 2 3/4'' to the back of one. That leave 1 3/4'' to the far side of the dry wall, a 1/2'' to spare. I think the newer boxes are deeper. With sloppy enough workmanship, I could see it happening. At least the finish wiring is usually done after the drywall, and we would hope the electrician would notice the screw coming through back of the box.
Certainly if the cable is screwed to the back of the box.

Be interesting to see what others have to say. Remember, Murphy was an optimist.

aggie_laser · Nov 25, 2007, 10:12 PM

thanks for the reply - just to clarify, this would apply to interior 2x4 walls only, so that there is sheetrock on both sides of the wall. Seems that the screws for the sheetrock at the back side of the wall could pentrate either the box, or wires - the back of an 18 cuin box is less than 1" from the sheetrock. The romex coming from the back of the the box is less than 1/2" from the sheetrock.

I'm also getting into a bit of a bind here with code for a bathroom (20amp GFI and 12/2 wire) with a light and fan switch in a two-gang box, with a branch to an outlet box, I'll have to use 22cuin boxes - the back of the box would be almost touching the sheetrock on the other side of the wall. Do I need to add some steel plates big enough to cover the box and wires around it?

the 18cuin boxes are also 2 3/4" deep, which only leaves about 1" from the back of the box to the sheetrock

many thanks for the help and advice

Cobraguy · Nov 26, 2007, 05:37 AM

Since nearly every home in America would be in violation, I would have to assume it's not a compliance issue. But it is an interesting point. I wouldn't be so worried about a sheetrocker running nails through the box as I would a homeowner sometime in the future. Let's hope they look at the opposite wall for things before they get carried away.

Stratmando · Nov 26, 2007, 06:54 AM

If you want to be safe, use metal boxes, Doesn't guarantee a screw won't go through one of the little holes in the back. You can't win.

labman · Nov 26, 2007, 09:43 AM

When I managed a factory, I never did get the guys to look at the other side before they cut a hole in the wall. I never remember finding out about anything worse than a few extra holes.