Putting electrical outlets in stone/masonry walls

[RogerT]

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?

[John Grabowski]

*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.

[bob haller]

OP should stud out te walls for insulation, fact is if the job has a permit its likely required

[RBM]

[RogerT]

Thanks. I just did a search for them online and that looks like exactly what I should be using. I didn't know that there was something called a masonry box -- duh, I guess I could have tried a Google search for that. But, again, thank you.

It does look like terracotta blocks to me. If I get a chance, I'll try to get a good picture of it and post it. It is very easy to cut and/or break out, partly because the blocks are hollow. I already had to do that in a few areas for other work I was doing

I do know about that code requirement, so that will be part of the plan. I will also be adding and outside outlet on the side wall next to a driveway.

There is no central air at this point -- just hot water cast iron radiator heat. That may mean that I'll want to include lines to each bedroom that can accomodate window AC units.

[RogerT]

I didn't think that insulating the outside walls will be required, but maybe it will -- so I'll check that out.

[RogerT]

I think I'll be okay with doing the short chases to the outlets without compromising the integrity of the masonry. Almost all of the wiring will be done in the open ceilings with only short runs up to wall outlets. If necessary, I could probably even do that by running conduit up to each outlet and then mortaring in the open chases around the conduit for more structural support. In the kitchen where there will be countertop outlets, all of those walls will already be framed out.

I hadn't thought about the possibility that I may be required to insulate the exterior walls now that the place is gutted. But, since you're the second person to mention that, it is something I will have to look into. I had actually been considering doing that anyway. My thinking was to frame out all of the exterior walls and insulate them. Although that would mean more work and more in materials, it would certain be a plus to have the walls insulated, and that would also provide the wiring access for outlets, switches, etc. The house is getting all new replacement windows -- possibly full-frame replacement windows -- which will also help in terms of preventing heat loss. One added problem with framing out the exterior walls is that the house has hot water cast iron radiator heat, and the radiators are, of course, on the exterior walls -- mostly under windows. So, if I frame out those walls, I will need to move all of the radiators in about 4+ inches. That means plumbing work, but since all of the other walls and ceilings are now open, access to all of the radiator plumbing is easy.

However, I posted this question about how to wire and mount the outlets in masonry walls in case I end up not framing out all of the masonry walls.

[RBM]

[John Grabowski]

*Since it is going to be a rental unit you should expect the worst from your tenants. You don't want them running extension cords or blowing breakers from electric heaters or air conditioners. Put each bedroom's outlets on a separate 20 amp circuit and make some of them double duplexes (Quads). You can go the extra mile and install one quad on a separate 20 amp circuit near a window for an A/C, but the one 20 amp circuit for all of the outlets will probably suffice with today's energy efficient air conditioners unless they are very large rooms. Pigtail the receptacles instead of feeding through each device for less maintenance down the road.

Current code calls for all bedroom outlets (As well as other areas) to be tamper resistant. Even if they are not required in your area I would still put them in. They prevent children from sticking things into the outlets.

How about posting pictures of the whole job and during different stages of the project?

[RBM]

They prevent children from sticking things into the outlets.

I don't know John, when I was around eight, I stuck a cut off lamp cord into an outlet. Flames shot out of the cut off end and scared the snot out of me, so I yanked the plug out. Couple of seconds later, I plugged that sucker right back in again, although this time nothing happened. Then I grew up and became an electrician... go figure

[bob haller]

Has OP considered upgrading to forced air? with AC?

Since code will almost certinally require insulation in a full gut job, and moving all those radiators:(

How old is the boiler?

[RBM]

First, why are you asking me? Second, since when is forced air considered an upgrade to hot water? Third, it's a rental which may not warrant central air

[aemeijers]

I'm a wimp- I'd do without indoor plumbing before I'd do without central air. But that is just me. If the place is a gut job, I'd definitely have the HVAC contractor cost it out both ways before I made a decision. If there are more than a couple weeks of hot weather each year at OP's location, central AC will definitely make it easier to rent and/or get a better price. Do they still do those systems with tiny high-pressure ducts, for retrofit to steam/water heated places?

Not a fan of hot water heat, personally. I like to have air moving around, more than convection provides.

[RBM]

Central air is just one more thing that the owner must pay for and maintain. It may be worth the investment, but then again this may be a section 8 situation, where it would become one more thing for the tenants to trash.

[RogerT]

I agree about trying to prevent future problems, especially since now is the best time to include all of the possible outlets and cirucits that will achieve that. I usually run a lot more than the minimum required number of circuits, and I put less than the maximum number of allowable outlets on each circuit. I also use nothing less than 12 guage wire in any circuit (no

14 guage anywhere), even though that may be overkill. And, with the exception of circuits that require 20-amp breakers (such as kitchens), I use 15-amp circuit breakers even though the 12-guage wire would allow 20-amp circuit breakers.

I am not sure what pigtailing the receptacles means. I know about pigtailing the grounds (which I learned here on this newsgroup), but I am not sure about what pigtailing the receptacles means.

[RogerT]

When I bought the property, I had the old oil-fired burner removed and I had a new gas-red boiler put in. At the same time, I asked about forced air heat and central air and the HVAC contractors recommended against it. They said that given the way that the building is constructed, and being a full

3-story building with no real attic above the third floor, it would be difficult to get cold air to really make it up to the third floor. Now that everything is gutted down to the studs and ceiling joists, I guess I could reconsider the idea of putting in duct work for central air. But, as much as I like central air, I am not sure it would be worth the effort in this case. As far as heating goes, I tend to think of "forced air" heat as being "scorched air" heat -- very dry, and not as efficient or even heat system as hot water cast iron radiator heat.

If I do end up framing out the exterior walls, moving the existing cast iron radiators about 4+ inches won't be too difficult.

[RogerT]

Since the place is now completely gutted, I may do that. I trust the HVAC contractor that I usually use, so it may be worth another look. But, my hunch is that trying to run central air duct work for this 3-story property may not be worth the cost and effort involved.

Yes, they are still available.

[RogerT]

If I do decide to add central air, I don't think I would be too concerned about tenants somehow trashing or breaking the central air system. The tenants will be paying all utilities, and I always get the heating/AC service contract that our local utility company offers. It makes life so much easier when a tenant calls in the dead of winter saying they have no heat, or in the heat of summer when they have no AC. I just call the utility company and they come out the same day and figure it out. Not everything is covered by the service contract, but most things are. And, by having the service contract I don't have to worry about finding someone who can come out and fix the problem.

[aemeijers]

Other alternative, of course, is to add holes for through-wall units on each floor. I'd find that preferable to window units, especially window units installed by amateur tenants 20-some feet above passing pedestrians. I window AC units. Can't open window, and almost every one I have ever seen rattles and leaks air and water in storms. IIUC, the sizes are now enough of an industry standard, that finding replacement units 10-15 years from now should not be a problem.

[bob haller]

My comments about AC was based on your installing or expecting window units. They are a PIA, are tough on the new windows your planning on installing, cost more to operate, and detract from the appearance of the building, and central air is more comfy too.

with the building gutted this is great time to get AC

Personally I prefer forced air, its more responsive to changing the thermostat, and elminates the intrusive radiators

Central air will be a positive at rental time