NM between joist bottom and sheet rock

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bobpaquette

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NM between joist bottom and sheet rock

I am noticing a common practice that seems to be largely tolerated of running 12/14 NM under joists in both new conceiled and exposed wiring in garages and housing. This practice puts the wire in the same gap as the sheetrock strapping. Where I am seeing this so commonly....am I missing a interpretation or loophole to 300.4?? Because, drilling and strapping and installing running boards is more time consuming not to mention the compedative disadvantage. I Appreciate your input and Thank You...It means alot to know that I'm not alone out here and can draw from the experience of other professionals.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Yuck. Doesn't sound any good to me.

This practice puts the wire in the same gap as the sheetrock strapping.
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I must be getting this wrong. Does this mean the NM is in between the edges of two sheets of sheet rock? If it does it sounds like it's going up after the rough inspection and while the sheet rock is going up or something. I can't even imagine an advantage to that.

Out of curiousity, do you see this going in or after the fact?
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Ok I`ll bite or get bitten what is sheet rock strapping ???Do you mean furring strips on a concrete deck?
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

It sounds like just what is done here in every wood frame house that is built.

Wood frame building in this area have 'strapping' or 'furring' strips attached to the bottom of the joists, then the sheetrock is attached to the furring strips.

This leaves a 5/8" - 3/4" gap between the joists and the sheetrock.

Cables are commonly run in that space, as long as it gets covered with sheetrock no running boards are required.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

As long as they maintain the 1 1/4 inch from strip i see no violation.We do the same thing on concrete block walls here.It leaves the wire between the sheet rock and block.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

1. The strap is 5/8" or 3/4" wood strips and is run on the bottom of wood joists (purpendicular to the joist just like I see these wires being run)
2. To maintain the required 1 1/4" they would have to increase the strap thickness or the sheet rock thickness by an inch or better.
3. The advantage happens when one saves time by stapleing the wire accross the bottom of joists instead of having to drill and fish.
4. And strangely, these houses are passing their rough inspections this way. Frequently, Building inspectors are acting as the AHJ for electrical. [Not enough ambitious retired masters to fill E-inspector spots at low wages ??]

Thanks
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

On the up side ...Its really easy to find any conceiled wire in the ceiling with a "Volt-tic" if the house is done this way.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

I've never seen new wood joists with this extra "strapping" added onto it, sounds strange for new construction.
I'm curious... Why is it even necessary?
Is it installed specifically for the wires?
Maybe so they can avoid drilling a large laminated beam or something? :confused:

Dave

[ June 06, 2005, 01:34 PM: Message edited by: davedottcom ]
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Wouldn't the requirement be for the cable to be 1 1/4" from the edge of the strapping where the sheetrock is attached? Does the NEC require it to be 1 1/4" away from the sheetrock or 1 1/4" away from the framing member supporting the drywall, in this case the strapping. There is a good photo of this installation on pp.258 in the 2005 Handbook.

[ June 06, 2005, 04:56 PM: Message edited by: infinity ]
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Originally posted by bobpaquette:
2. To maintain the required 1 1/4" they would have to increase the strap thickness or the sheet rock thickness by an inch or better.
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Bob please show me the code section that requires cables run perpendicular to the framing members to be 1.25" back from the rock.

The cables are not in bored holes, or notches.

Perhaps it's a loop hole but that fact is it is a very common installation that works fine. :cool:
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Originally posted by davedottcom:
I've never seen new wood joists with this extra "strapping" added onto it, sounds strange for new construction.
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It is required in all construction in MA and RI as far as I know.

I do not know why, but I doubt it's for the wires.

Even my 1925 house has the strapping.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Maybe I'm not understanding this whole practice. (I had it wrong in my first post)

How does 300.4(B)(2) not apply?

A better question, if I understand this right, how is it that the NM isn't full of nails and screws by the time the sheet rock's up?
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Originally posted by physis:
How does 300.4(B)(2) not apply?
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300.4(B) does not apply at all to wood framed buildings. :D

300.4(B) Nonmetallic-Sheathed Cables and Electrical Nonmetallic Tubing Through Metal Framing Members.


Originally posted by physis:
A better question, if I understand this right, how is it that the NM isn't full of nails and screws by the time the sheet rock's up?
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Well there is about 14" between strappings, if your a good installer you locate the NM in the middle of that 14" so the drywall guy would have to be off by 7" to hit the cable.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

It use to be comon here to see trusses get the 1x2 strips but now all they new is screw the drywall to the truss.I think this install meets the code and would be fast and very safe.If there is a danger what is it ?
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Originally posted by jimwalker:
It use to be common here to see trusses get the 1x2 strips but now all they new is screw the drywall to the truss.I think this install meets the code and would be fast and very safe.If there is a danger what is it ?
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Jim should I tell the framers that you said it was OK not to use strapping? :D

Different areas different codes.

I have heard a lot of explanations about the purpose of the strapping none of them made much sense. :confused:

Does anyone here know?
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Well of course that refers to metal framing Bob, what was I thinking.

7 inches "max". Alright, but I don't like it a lot too.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

What about for sound deadening? Attaching a thin wood strip perpendicular to the joist allows you to have a very small contact area between the two wood surfaces which would keep sounds that are hitting the sheetrock form travelling through the entire joist. In commercial construction it is common to use a 1/2" channel that gets attached perpendicular to the studs with only one screw which limits sound transmission. I've seen these used on walls enclosing electrical closets that had noisy transformers.
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Sam from reading all the posts here I have come to a conclusion.

The inspectors in this area have a different view point in regards to what will happen.

IMO in this area inspectors do not expect NM or SE to be a magnet for physical damage.

I think this is backed up by our always less restrictive NM rules. I can still run NM above a commercial ceiling here.

SE services are very common, along with NM running exposed from the floor joists down to the foundation wall mounted panel.

In many areas the view point seeems to be anything and everything will happen to the NM, kind of a pessimistic outlook. :roll:
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Strapping is used here also_One reason..trusses are often 24 inch centers.Strapping is run across the trusses at 16 inch centers...it keeps any potential sagging of the sheetrock minimalized.Also trusses can tent to want to sway..the strapping ties them all together..no movement.The strapping is NOT there to run wires..but is nice for fishing after the fact.The same goes for floor joists...ties them firmly together and prevents screw pops.
Ross
 
Re: NM between joist bottom and sheet rock

Re: NM between joist bottom and sheet rock

Well don't blame me Bob. If I use NM where there's even the remotest possibility that something inprobable could happen the building department will cordon off the area and evacuate everybody in a two block radius after they've called to have the grid shut down. Ok I'm exaggerating again :D

I'm just used to it being treated as more of a hazard than a wiring method. I used to think it was over kill too. Some of it I still do. I have to agree that NM does get to much unnecessary attention. I guess after a while your thinking gets aligned with the practices.

I still feel like it's too easy to put a fastener through it in this case but if it's not statistically an issue then I'd agree that I don't need to be all worried about it. Still doesn't sound consistent with the rest of the requirements though.

:p
 
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