Minimum depth of device box on firred-out walls?

[olc]

What is the minimum depth of a device box that can be used to install a receptacle or switch?
Box would be installed in firred-out drywall on top of an existing masonry wall. Perhaps MC cable into the box. Probably should assume two MC cable connections (wiring in and out).
Would a 2-1/8" box work with the open of the box at the outside face of the drywall (1-1/2" firring)?
1-1/2" box (1" firring)?

 

[infinity]

In my experience with an 1.5" deep box and a mud cover it won't fit with 1.5" furring. They do make 1.25" deep boxes for this application.

 

[Martin B]

Check out sec. 314.16 in the NEC. There are a couple good tables for calculating box fill and minimum size box

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[olc]

In my experience with an 1.5" deep box and a mud cover it won't fit with 1.5" furring. They do make 1.25" deep boxes for this application.

So if presented with 1-1/2" furring and drywall, wiring and devices could be installed one way or another?
How about the wall boxes for surface light sconces?

Would 1-1/2" furring be the minimum? (for boxes)

(an architect is asking)

 

[infinity]

So if presented with 1-1/2" furring and drywall, wiring and devices could be installed one way or another?
How about the wall boxes for surface light sconces?

Would 1-1/2" furring be the minimum? (for boxes)

(an architect is asking)

For a lighting box you can add the thickness of a layer of drywall to the dimension provided by the furring because the box will be flush with the finish.

 

[JFletcher]

There is no minimum depth, only box fill and cubic inches. You might use a box like this:



to be shallow enough for firring yet have enough ci to work with.