I am planning a complete rewiring of a house that I own,. and I am trying
to figure out how to place the new interior outlets in the existing
exterior walls that are made of stone/masonry. I previously posted about
this property regarding sheetrocking, electrical subpanels, etc. The house
will end up being a rental property.

The property is a 3-story side-by-side "semi-detached" twin home with a
full unfinished basement. I own one side of the twin and someone else
owns the other half next door. All of the lath and plaster has been
removed from the interior walls and ceilings down to the studs and joists.
However, all 4 of the outside walls (front, back, and two sides) are
stone. I say "stone", but it's some kind of red clay-looking blocks that
are stacked on top of each other. Those 4 exterior walls then have a
rough coat and a finish coat of plaster applied right on the stone to
create the interior side of each of those 4 exterior walls of the home --
no lath, just stone and two types of plaster on top of the stone.

My question is about how to place outlets in those stone/masonry walls. I
don't want to do surface mounted outlets and wiring if I can avoid that.
I can easily notch out the openings for the outlets, and notch out a path
up from the floor to each outlet to get the wire to the outlet. The
wiring will come in from underneath via the now-open ceilings from the
floor below.

But, how do I actually mount the electrical boxes in place? Would I just
place the boxes, run the wires to them, and then just mortar the boxes in
place? If so, is there any particular type of box that would be good to
use -- metal, plastic, old work, new work, etc? I will be getting a
permit, and this will end up being inspected before the walls are closed
up, so whatever work I have done will need to meet the applicable code
requirements.

Or, is there another way that electrical outlets are typically wired,
mounted, and secured within masonry/stone walls of a home?


*There are metal electrical boxes made for masonry which you should be able
to get at an electrical supply house. Raco has the #690 one gang which is
2.5" deep or the 695 which is 3.5" deep. Steel City numbers are GW-125-G
for the one gang 2.5" and GW-135-G for the 3.5" depth. The masonry boxes
are also available in multiple gangs. Don't use plastic boxes for this. I
am not sure they are approved for this type of installation.

It sounds as though you have terracotta block. You can fish wires through
that if there isn't too much residual cement and debris inside. You would
have to cut holes for the boxes and then cement them in place. The
terracotta block can be hard. You may need an angle grinder with a diamond
blade to cut through it neatly. Instead of cable, you could use flexible
conduit to feed the box so that you can add or replace wires down the road
without having to remove the box.

You are also required to have an outlet outside in the front and in the
back. If there is an outside air conditioning condenser you will also need
an outlet for servicing purposes near that unless the front or back outlets
are close.