Sunday, May 27, 2018

USA New Wall - The never ending question of electrical boxes

Now that thousands of people have learned about the USA New Wall model for easy to build high performance wall assemblies the single most common question is how do you put electrical boxes in the utility cavity? It could not be easier.

Here is the explanation one more time:

In the 1.5" wiring chase you use 4x4x1.5" square boxes. These actually have a few more cubic inches inside than a regular switch box. Then you use a reducer cover to take it down to a normal switch plate - the reducer has a 1/2" or 5/8” extension that reaches through the drywall.

like this:
4x4 box example
4x4 box another
You can screw the box through the back in to the studs, or attach via top or bottom into the horizontal furring. So you actually have many more location options.

and this is the reducer cover:
reducer cover example
reducer cover another
also comes in 5/8” & 3/4” if you have tile or paneling.

and double gang for two devices in one box:
double gang box cover

Hope that is clear. This is straight forward - you can find these parts on the shelf in Home Depot.

As far as having only 1.5” of cover over the wire - this is code minimum and its acceptable. Consider a 2x4 stud with a 1/2” hole in the middle to pass a wire. That stud offers 1.5” of wood cover for the wire. So with this wiring chase with 1.5” furring the wood cover is identical to working with a 2x4 stud wall. This only applies where the wire passes behind the horizontal furring - because this is the place where fasteners will go to attach the drywall. Between the furring strips this does not apply. To run horiontal you simply tack the wire to the face of your studs through the vapor sheet. Note, this is faster and easier than fishing every wire run through a hole in the studs. Don't let an electrician argue that its harder, because it is not.


  1. Glad you aren't dead! Long time, no posts.

    1. No, I'm not dead, just too busy to blog.

      The electrical wiring questions continues to be one of the most frequent "how do you" I receive. Lots of people getting bad information out there telling them that this is impossible or against code. A clash on a local project gave me the opportunity to escalate the question to the State Code officials who agreed with my reading of the Code. I now have an informal opinion letter from the state which brings down the defenses of electricians and inspectors.

  2. One can also apply a metal wire guard to the furring strip, if the 1 1/2 inch distance is of concern.