[coder34]

Here’s my situation:

I have a forty year old house with plaster over drywall and lathe construction on the outside walls—no studs. This means there is only about an inch of space to run wires in those walls. I really need to make some updates to some circuits and get rid of the current aluminum wire, maybe add a sub panel The current receptacle boxes on outside walls are 3 by 2 by 1.5 (8 cubic inches) and are used to make middle runs, and so have 4 insulated wires inside them and no insulated caps—1 set of incoming wires, 1 set of outgoing wire, both connected on the receptacle itself, no pigtails.

The space between where the brick and vapour barrier end and the interior drywall and plaster begins is only about three quarters of an inch—and that’s all you’ve got for running wire. The plaster and drywall might give you another inch but are not thick enough to accommodate even a 2 inch deep (10 cubic inch) receptacle box, without that box not being flush with the interior walls.

The 2007 CEC code for Ontario says (Rule 12-3036 concerning box size) that an 8 cubic inch receptacle box can contain a maximum of 3 insulated wires. I assume you can begin to see the problem.

Furthermore, I am unclear as to whether the Code requires “pig tailing” for middle runs or not which would require 6 insulated conductors in a box and really make my problem worse.

The only solution that I can see that would totally satisfy Code would be to run a given branch circuit wire in the basement and put a series of junction boxes on this wire, from which a separate 2-strand arm would go up two floors (for the bedrooms, for example) and power each outside wall plug. The basement either has unfinished or false ceilings so the junction boxes would be accessible. While I understand such an odd and messy method is not specifically prohibited by the Code, it might well be more than looked down upon by an inspector. Or, I’m looking at adding a layer of drywall on every outside wall.
So I’m not sure what to do. I guess my question is, do inspectors take into account your whole situation and let you “slide” on what seems an impossible situation given how your house was built, or are they slaves to the written code? Or is the 2007 code only for new houses? In short, what should I do?

Thanks so much for helping, if you can.

[tkrussell]

USA electrician here, I don't think we have any Canadian experts, so I will do my best.

You can use a 4" x 4 " x 1.5" deep, with a flat single device mud ring at each outlet location, but will need a two gang cover plate with one duplex.

This assumes you have a total of 1.5" deep available.

You may be best with the junction boxes above/below each outlet, and have the one two wire cable feeding each outlet.

No inspector will let wire fill of a box slide.

[coder34]

Thanks tk. Will investigate the mud ring, but agree I may be best with junction boxes. Hopefully an inspector will understand the need of for many of them.