I am working on an old apartment with plaster on masonry block walls and plaster ceilings. The electric wires are armored cable embedded in the plaster. I want to run additional lines to serve new ceiling lights in a couple of the rooms. What is the best way to cut the channel in the plaster in which to embed new armored cable? I’m thinking that a diamond bit for a laminate trimmer/router/Dremel/RotoZip would be a lot faster and neater than a chisel…
Also, according to my NEC wiring book, Romex would not be NEC compliant, but armored cable would. Can anyone confirm/deny this? Does it matter if the armor is aluminum or steel?
Thanks.
Replies
FWIW, I would put a diamond blade in an angle grinder to cut the channel then use non-metallic conduit through which I would fish NM cable. Aluminum jacketed cable is not acceptable as far as I know.
333 & 334 of the 1999 NEC. Both AC and MC cable are permitted to be embedded in plaster as long as it is not in a wet or damp location.
I second the motion to use a diamond blade in a 4" grinded. If you don't have one, this is an excuse to buy a new tool.
Seems to be no dofference between aluminum and steel.
~Peter
Martha Stewart has discovered that there is a double edged hacksaw blade built into each carton of Aluminum foil. Expect her to be out within four months.
Edited 11/29/2004 10:59 pm ET by PM22
Thanks for the replies. Unfortunately I already have a small grinder, so no new tools this time around (except for the blade). I think I'll try to rig the vacuum hose to the grinder to suck up some of the plentiful dust that I'm sure this process will generate...
PM22,
not that i have ever embedded nm in plaster but i thought that was ok? when i have had to embedd i have used mc for fear that a H.O. may drive a nail or staple into the conductor.
boy i am lazy i am typeing this and stareing at my nec on the bookshelve next to the monitor, oh well
james
Indeed you got the secret code in the Code right. NM is the secret term for non-metalic sheathed cable. In other words, Romex. Non-metalic can be wood, concrete, leather, feathers, wool or even plastic.
Anyway, it is 336-5 (b) in the '99 edition: not be installed... (2) Where embedded in masonry, concrete, adobe, fill, or plaster. If it breaks, you can't put it in a plaster cast.
~Peter
After her escape, Martha Stewart intends to hideout in Davis, California. You heard it here first. Don't tell.
natterd,
When i need to do this i dig thru my routerbits and find the most discustingly dinged straight 3/4" bit i can get and drag my 3.5h Royobi stump grinder router thru the plaster, that POS will not die and i have tried killing it with much abuse. I get a nice uniform slot for mc but the dust is killer, a vac dose help but there is no way i am going to subject my festool router with dust collection thru that.
james
This I like. I have an old router that I picked up for $30 at a garage sale that'll work in this situation. As for the dust, I agree it will be the worst part- I did some cutting for another project with a diamond blade and the dust was insane.
Natterd,
Good choice going with the router, just make it one you want to die and it will continue to cut plaster untill the cows come home... If i had a buck for every time i tried to kill that awfull ryobi i would have two festool routers.
get out the tarps and plastic and safty glasses, respirator, fan, and vac and just get the slots cut, playing about any other way is for the birds.
james
Don't use chisel--the pounding will probably break the "keys" in nearby plaster and cause lots of cracks and loose plaster. Other posts proposing grinders or old routers and bits are good.