Minimum Box depth for receptacles and devices

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steve66

steve66

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Illinois
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Engineer
Is there a minimum box depth for flush mounted receptacles and devices?

I have a project where we will have masonry walls with 1-5/8" furring strips, and 5/8" drywall.

The idea is to put the conduit and boxes in the furring strip space between the masonry and drywall. That would allow a 2-1/4" deep box to be used.

Is that a deep enough box for installing receptacles?

For more wiring space, we could spec. 2" furring strips. Or I could spec double gang boxes with a plaster ring for single duplexes.
 
steve66 said:
Is there a minimum box depth for flush mounted receptacles and devices?

I have a project where we will have masonry walls with 1-5/8" furring strips, and 5/8" drywall.

The idea is to put the conduit and boxes in the furring strip space between the masonry and drywall. That would allow a 2-1/4" deep box to be used.

Is that a deep enough box for installing receptacles?

For more wiring space, we could spec. 2" furring strips. Or I could spec double gang boxes with a plaster ring for single duplexes.
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If I were looking at this, I'd use a standard 4" square 1-1/2" deep metal box ( 1900 J box ) with a single gang plaster ring with 5/8" rise. Fasten the box and conduit straight to the masonry wall.
 
steve66 said:
I have a project where we will have masonry walls with 1-5/8" furring strips, and 5/8" drywall.
I could spec double gang boxes with a plaster ring for single duplexes.
Click to expand...

A 1 1/2/" deep, four square (1900 box) and 3/4" plaster ring should work out OK. That's what I would use.


Al is right you will pick up that 1/8" just with the plaster ring so a 5/8" would work just fine.
 
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using same dimension mudrings as drywall never seems to work out. One size up over drywall dimension seems to be what people do here. 5/8" ring with 1/2" drywall.
 
USMC1302 said:
using same dimension mudrings as drywall never seems to work out. One size up over drywall dimension seems to be what people do here. 5/8" ring with 1/2" drywall.
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Yes, that's true for a floating 1900 that is not sandwiched against a masonry wall. Most installations of 1900s to framing allow the 1900 to squirm a bit. If the 2-1/4" that Steve specs is fact, a 3/4" ring will stand proud of the drywall a skosh.
 
Let me tell you, you do not want mud rings or boxes standing proud of sheetrock! It takes a lot of time/mess to correct this by grinding or other methods, even with plastic boxes. And when does the electrician usually find out they are proud? After the wall is painted of course.:eek:
 
Frank DuVal said:
Let me tell you, you do not want mud rings or boxes standing proud of sheetrock! It takes a lot of time/mess to correct this by grinding or other methods, even with plastic boxes. And when does the electrician usually find out they are proud? After the wall is painted of course.:eek:
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haha! Correcting a small amount (1/8" or less) of ring sticking out can usually be accomplished by cutting the raised bosses off of the back of the coverplate, but yeah, you dont want a metal mudring sticking out of a wall - you cant grind it because there will be nothing left to attach the device to.
 
I don't remember where I got them, but I used a box on a re-mod once that an inspector told me about. He called them 'pregnant boxes'. They had a very shallow profile, but a generous space to one side, behind the drywall, for additional volume. They were great. It's been so long since I used them I apologize for not having a link or a source. But the job was furred out concrete walls and the 'pregnant boxes' made things so much nicer.
 
K8MHZ said:
I don't remember where I got them, but I used a box on a re-mod once that an inspector told me about. He called them 'pregnant boxes'. They had a very shallow profile, but a generous space to one side, behind the drywall, for additional volume. They were great. It's been so long since I used them I apologize for not having a link or a source. But the job was furred out concrete walls and the 'pregnant boxes' made things so much nicer.
Click to expand...

this is the 'pregnant box'
 
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