Wiring re-model work: NM + nailplates vs. BX behind baseboard

[jumpind]

I have an old house, complete with plaster+wood lathe walls. The master bedroom upstairs is fed from an overloaded old circuit that I want to replace with a new branch circuit.

I see two options; NM and amored cable. The NM option is use all NM cable for feeds to outlets, and at every stud, remove the plaster, snake the cable past the stud, and put a nail plate in. This would obviously require alot of patch work and painting. The BX option is to use all armored cable by removing the baseboard trim, securing the cable behind it and go up to each recept. from there.

Because I need to get past a few door frames, using all armored cable seems to make sense. I have seen this trick in several DIY books.

Is there any issue with this approach?

[John Grabowski]

Just because BX has a metal jacket does not mean it is impervious to penetration by nails or staples. I've been on jobs where contractors have shot nails with their nail guns through the safety plates I installed.

Is there an attic or crawl space above the bedroom? If so then the best way to go is by fishing the wires down the walls from above.

Try to cut your outlet holes adjacent to a vertical wall stud. That way you can screw your metal outlet box directly to the wood stud making it more secure. Depending on the condition of your plaster, you may be doing a lot of patch work anyway as the plaster cracks and breaks as you cut into it. I usually line the cutout with 2" duct tape or masking tape to keep it stable before I cut any holes, but there are no guarantees. Removing the baseboard can also cause the plaster to crack and break.

I think that the easiest method is to get a 5" or 6" tungsten carbide tipped hole saw (McMaster.com) and at a slow speed drill on the center of each stud. Then chisel out (Or drill with smaller hole saw or bit) a small notch in the stud for NM or BX and put a safety plate over it. If you were careful drilling, you will have a round piece of solid plaster that can be plastered back into the hole it came out of. Removing moldings around doors and floors can be quite messy in old plaster rooms and you must put back all of the moldings that were removed.

[sylvan butler]

Nasty.

No attic or basement crawlspace?

Why not just open a small hole (outlet box sized) and use a flexible drill bit to drill thru about 5ft or 6ft of studs to the next place you need an outlet?

Cost (probably less differnce now than there used to be). Ugly cable will be in the way at some future point in time. I've used it before. Sometimes it is the best immediate solution.

sdb

[RBM]

I'm gonna echo John G, wood lathe plaster can be a nightmare. I've had entire ceilings fall while trying to cut some small holes. Once the keys break off the lathe, there is no integrity in the stuff at all. Try to work through attics and basements and definitely whenever possible attach boxes to studs and disturb the least amount of plaster possible

[Don Young]

Plan your outlet placements to minimize cable runs horizontally in the walls. It is worth using a lot more cable going up and down. In the past I did a lot of old house wiring and rarely notched studs or ran wire behind baseboards, although it is sometimes necessary. It is fairly easy to drill through one stud by drilling through a close outlet hole. If you place another outlet on the other side of the wall just beyond the second stud you can drill through it from that hole. With a flexible drill you can drill through the studs on both sides of an outlet opening. You can also drill through several studs next to a doorway using drill extensions and then plugging the hole in the door jamb.

Plan your work carefully and use your imagination to figure out how to get your wires into the required spaces or whether to move your outlet to a more accessible space. If you know an experienced old-work electrician he could give you some ideas.

Don Young

[Tom Horne, Electrician]

As others have stated metal jacketed cables are not immune from damage by nails and screws.

1) Remove the baseboards from all of the walls to be cabled. 2) With a masonry cutting blade in a circular saw cut the plaster clean through just below the top of the baseboard. 3) Remove the plaster and lath below the cut line completely. 4) Bore your holes through the center of the stud using a nail eater bit and a right angle drill motor. As long as these holes are an inch and a quarter back from the face of the studs you are not required to apply kick plates. 5) Pull the cables. 6) Apply appropriate spacers to each stud and reinstall the baseboards.

Alternatively Perform steps 1 through 3 above and

4) Replace the baseboards with divided surface metal raceway. 5) Install cap molding to make the surface metal raceway appear to be baseboard. 6) Glue the toe moldings to the surface metal raceways removable covers. You now have a two compartment raceway that can be reopened any time you need to add or change wiring without disturbing the interior finish of the room. Receptacle and communications outlets can be fished from the cut in openings in the existing walls to the back of the surface metal raceway or installed in the raceway itself. In my opinion surface metal raceway is only worth doing in rooms that are likely to see a lot of rearranging of the wiring such as an extensive home entertainment setup or a truly heavily used home office.

[jumpind]

Thank you everyone for taking time out to help. I have access to one wall from a crawl space, but from there I'm on my own. I think running the NM cable sideways will be cleaner and keep the plaster damage down to a minimum.

Notching the stud and getting the nail plate in would be impossible without severing the lathe straps, which are mounted directly onto the stud. The studs are also sideways back-to-back, not like newer construction, so I'd have to drill through 4" of elderly timber. Couldn't I just sneak the cable in between the straps of lathe and cover that with plates? That does sound remarkably easy, though. Too easy.

Thanks - dan

[John Grabowski]

With the studs flat like that you will not have enough depth in the wall to install a decent size outlet box so that you could go from outlet to outlet. You could use a 4"square x 1.5" deep box with a plaster ring, but that involves making bigger holes.

Have you considered using Wiremold? You could run it along the baseboard so that it blends in with the molding.

If you will be using 14/2 NM you could just notch some of the wood lathe to fit the cable through and put a nail plate over the wood lathe.

[Doug Miller]

Yes, he will. A lath-and-plaster wall is typically about 3/4" thick, which allows a 2 1/4" deep box even with the studs laid flat.

Not necessary to notch the lath. There should be plenty of room to lay 14-2 between the lath strips -- but it does need to be covered by a plate.

[John Grabowski]

Unfortunately a 2" x 3" x 2 1/4" metal box is only approved for 5 #14's. After deducting two conductors for the device he would not be able to feed from outlet to outlet using that size box. He would also need to use an outside connector instead of a box with internal clamps as a one conductor deduction is required for that as well.

[Doug Miller]

Nothing stopping him from ganging two such boxes together...

[John Grabowski]

That will work. Good point.

[hex]

Could I gang two of those boxes together and make a quad receptacle outlet? That would meet the fill requirement:

2 x 2 devices + 1 clamp + 4 conductors = 9

I am concerned having single duplex receptacles with two-gang sized faceplates would look sloppy. Then again, I can't say I have seen a bedroom with all quad outlets before.

dan

messagenews:DXv%g.914$ [e-mail]...

Good point.

[jumpind]

Could I gang two of those boxes together and make a quad receptacle outlet? That would meet the fill requirement:

2 x 2 devices + 1 clamp + 4 conductors = 9

I am concerned having single duplex receptacles with two-gang sized faceplates would look sloppy. Then again, I can't say I have seen a bedroom with all quad outlets before.

dan

John Grabowski wrote:

[gfretwell]

I put quads in my bedroom. Next to the bed they are handy for all the stuff you end up plugging in. The ones that ended up away from the bed the second device slot got the green flourecent nightlights that fit in a decora cover. They throw a soft light and only draw a milliamp or so.

[jumpind]

Oops, that should be 10 even, I needed to add a single volume for the equipment grounds:

2 x 2 device + 1 clamp + 1 EGC + 4 conductors = 10

Great idea about the second non-receptacle like device. I'll consider that an option.

dan

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