an electrical contractor wants to use romex to rewire a house that has solid block walls. the walls will be coverd with sheetrock, about 1 inch hollow will be between the sheetrock in the block wall. have you guys ever hear of such a wiring pratice? any advice ? any code violations in the above procedure ?

I know there has to maintain an 1 1/4" space between romex and finish surfaces. I believe m/c falls in the same class. I would prefer emt with surface mount 4" sq's and apply the proper plaster ring to finsh surface.

MJ:
Besides the romex situation, what kind of box is the installer proposing???
From your post, I assume that furring strips aregoing to be fastened to the block wall, and sheetrock will be attached to the furring strips. You cannot staple/strap the RX to the furring strip sides, as you cannot maintain 1 1/4" of clearance to prevent nail damage. 1/2" EMT would work, but you have to install a box.
John

thanks,hotline... i forgot about the 1 1/4 rule and also the depth for the boxes.

Guys,
What code section can you cite for this application?
Don

thank you Don,

(i guess we have an inherent 1 1/4" fixation ....)

300.4(D) states framing members, such as 'joists, rafters or studs'....does 'such as' also include furring strips??

I've always used 1-1/2" Deep 4x4s and 1/2" (or 5/8") plaster rings. 3/4" EMT for physical protection of the NM-B Cable up to the area above the ceiling.

Don, please let me know if this is overboard, it's darned expensive on a bid job!

Sparky,
I think that is the way to go, but I just can't find a code citation to require that type of protection for this appliction.
Don

i do the same Virgil, with these on the cieling end;



btw;
have you guys seen those who run nm aside furring strips on cielings? not my cup of tea, yet i do not believe in violation..

Dude! Where do you get those!

I use emt connectors and remove the locknut, put on a bushing, and make sure it's stapled within 12".

Those are awesome! I wonder if my supplier has 'em?

[This message has been edited by sparky66wv (edited 11-20-2002).]

they should, ask for an emt-nm conn.

The adapters pictured are readily available. Home Depot even has them.
On bloc wall jobs I have used NM straps screwed into the block at about 2-3" from the furring strip. If you punch out the block and nail a metal box with a side bracket to the furring strip the cable can be fed into the box. I have done several jobs this way and never had a problem passing.
BTW,
Where can the requirement for 1 1/4" to finished surface be found?

I know this doesn't help the queries re whether this is a violation of the NEC, but it's a situation that crops up regularly in British wiring where brick and block walls are very common.

The common approach is to run the NM on the block wall and "protect" it with galvanized steel channeling before the drywall is installed.

I put protect in quotes, because it doesn't really offer that much protection against a nail or drill.

I didn't know you could run NM cable through conduit?

I thought conduit was only listed for individual wires.

thanks pauluk, the gal steel channel sounds like a great idea to protect the cables from physical damage.

SvenNYC,
check note 9 to Chap 9 Tables (pg 70-617 2002) ,i believe it alludes to nm and similar wiring, listings aside of course....

Paul brings a point of interest,
(insignificant to this thread but of worthy mention) in that a 'channel' may not encapsulate 360 deg's as a conduit....so derating/conduit fill flys out the window...

[This message has been edited by sparky (edited 11-21-2002).]

Around here we wire plenty of concrete block homes.

We use what is called a romex stand off strap. It is a plastic device that is nailed alongside of a furring strip. It has grooves that the romex slides into and it keeps the space from the furring strip at 1 1/4".

We use plastic metal bracket boxes nailed to the furring strips for installing devices.

Locate the box in the hollow of the block and knock a hole in the wall. Use spray foam around the box after the job is done to seal up any air leaks. The spray foam also helps hold the box in the wall too.

For horizontal runs of nm notch the furring strips and run the wire through. Use nail plates over the romex to protect the wire from being hit by a drywall nail.

All of this pases local inspections and the cost is very reasonable both to the electrical contractor and customer.

Two man average crew can do a 1400sf house in about 2-3 days. Down here our houses don't have basements though.

fla sparkey, can you give more details about the romex on block walls? are could someone post a photo of the procedure?

Sorry mj, I don't have a digital camera yet. Kind of hope to maybe get one for Xmas this year.

Because we wire a lot of block houses the local supply houses carry the plastic standoff straps I described. The metal nail plates are a standard item as well.

You might try Lowe's or the big orange box for these items and the boxes as well.

Installing an electrical system this way is fairly simple.

If you have a specific question or two I will try to answer them for you.

mj,
Are these solid block walls or are they the kind that I am use to,16in with a center web and open cells on both sides of the web,except around openings when they are filled with rebar and concrete?
Down here in the Sunshine state there are a lot of block homes that use open cell blocks that are suitable for running NM in the open vertical cells.This will protect the cable from just below the lentil or header block down to the slab.
For cables behind sheet rock we are required to keep the NM 1.25 inches away from any framing member and that includes the furring.There is a stand off clip that screws into the furring and keeps the wire offset the proper distance.We also have used cut nails and wire ties for this purpose.Plastic boxes are punched into the open cells in the block and secured with furring and cut nails.
Once the rough in is inspected then the cells are filled wth foam for better insulating properties.This will not prevent the home owner from driving a long nail or screw into the cable unless the cable is in the cell.
Chris

I am sorry to repeat what Fl Sparky posted.I was interrupted while I was typing my post.
Chris

thanks chris, you explained it well. i am an electrical contractor and aslo an electrical inspector. an electrician asks me about the above procedure. now i can tell him that it will be accepted, and is code compliance.so now i can tell the Mississipi guys about a new trick of the trade.

A single hammer blast on a hollow wall about 8" above or below the box allows the NM cable to be fed inside the block and inserted into the box. No excess chipping above or below the box to insert the NM cable required.

Two questions,
Has anyone talked to a mason about "blowing out that many blocks????

second;
I know about the 1 1/4inch rule or a 16gauge nailing strip. But is there anything on the thickness of the wall cavity????

I always ran my runs verticaly into the ceilings and puchased a 2inch piece of 16gauge steel and ran it up th furring strip all the way to the cieling.