specifics on use of wire protector-plates with NM-B?

[808Pants]

https://www.ecmweb.com/qa/code-qa-protection-options-type-nm-cable apparently covers the extent of what the NEC says about this topic, but in jobsite reality, it appears this omits any specifics as to where wire-protection plates (https://www.lowes.com/pd/STEEL-CITY-2-1-2-in-x-1-1-2-in-Gauge-Nail-Plates-100-Pack/3422476) are required. In typical wood-frame construction for Hawaii, where insulation in walls is rare, 2x4 studs are the norm. So a run of NM-B through studs will be "protected" behind (3.5"/2=) 1-3/4" of lumber, minus half the hole diameter, plus the thickness of the wall sheathing - or about 1.5" of wood/gyp, minimum. Is that considered adequate depth by NEC? or is this a judgement call?

The plates are cheap and would be relatively easy to install, even everywhere a wire passes through a stud, but I'd rather not worry about bulges in sheathing material in otherwise-flat wall surfaces, which can jump out from certain lighting conditions.

 

[infinity]

The measurement is from the stud face back to 1.25". If the hole is in this area then one of those plates or some other protection is required. With a 3.5" wood stud you use a 1" hole in the center of the stud and still not need the protection. (3.5"-1"=2.5"/2=1.25")

You do not count the finish as part of the 1.25" measured dimension.

 

[romex jockey]

https://www.ecmweb.com/qa/code-qa-protection-options-type-nm-cable apparently covers the extent of what the NEC says about this topic, but in jobsite reality, it appears this omits any specifics as to where wire-protection plates (https://www.lowes.com/pd/STEEL-CITY-2-1-2-in-x-1-1-2-in-Gauge-Nail-Plates-100-Pack/3422476) are required. In typical wood-frame construction for Hawaii, where insulation in walls is rare, 2x4 studs are the norm. So a run of NM-B through studs will be "protected" behind (3.5"/2=) 1-3/4" of lumber, minus half the hole diameter, plus the thickness of the wall sheathing - or about 1.5" of wood/gyp, minimum. Is that considered adequate depth by NEC? or is this a judgement call?

The plates are cheap and would be relatively easy to install, even everywhere a wire passes through a stud, but I'd rather not worry about bulges in sheathing material in otherwise-flat wall surfaces, which can jump out from certain lighting conditions.

https://www.homedepot.com/p/RACO-2-...sz5h3XUQsi7sBevzrmEaAribEALw_wcB&gclsrc=aw.ds

~RJ~

 

[hbiss]

...Is that considered adequate depth by NEC? or is this a judgement call?

No, it's really quite specific:

300.4(A)(1) Bored Holes. In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed through bored holes in joists, rafters, or wood members, holes shall be bored so that the edge of the hole is not less than 32 mm (11⁄4 in.) from the nearest edge of the wood member. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by screws or nails by a steel plate(s) or bushing(s), at least 1.6 mm (1⁄16 in.) thick, and of appropriate length and width installed to cover the area of the wiring.


-Hal

 

[MAC702]

2x4 studs are the norm on the mainland, also. Nail-plates are usually only used when the hole can't be in the middle of the stud for some reason.

 

[electrofelon]

In addition to what the NEC says, I think some common sense comes into play too. I stay away from behind kitchen and bathroom cabinets that will be fastened to the wall (with a potentially unnecessarily long screw) or use nail plates liberally there. A few jobs ago had the heating guy drive a lag bolt thru my wire when mounting a radiator. I would have used nail plates behind them if I had known they were going in. I ask more questions now.

 

[romex jockey]

nail pates are cheap insurance on any rx job

~RJ~

 

[kwired]

In addition to what the NEC says, I think some common sense comes into play too. I stay away from behind kitchen and bathroom cabinets that will be fastened to the wall (with a potentially unnecessarily long screw) or use nail plates liberally there. A few jobs ago had the heating guy drive a lag bolt thru my wire when mounting a radiator. I would have used nail plates behind them if I had known they were going in. I ask more questions now.

don't run cables horizontally in the wall period where cabinets are expected to be mounted. They always use longer screws that have a good chance of hitting your cable that is otherwise code compliant. If they hit steel plate, good chance they will get out prope drill bit and drill through it and you have no protection anyway if they do that.

 

[kwired]

https://www.ecmweb.com/qa/code-qa-protection-options-type-nm-cable apparently covers the extent of what the NEC says about this topic, but in jobsite reality, it appears this omits any specifics as to where wire-protection plates (https://www.lowes.com/pd/STEEL-CITY-2-1-2-in-x-1-1-2-in-Gauge-Nail-Plates-100-Pack/3422476) are required. In typical wood-frame construction for Hawaii, where insulation in walls is rare, 2x4 studs are the norm. So a run of NM-B through studs will be "protected" behind (3.5"/2=) 1-3/4" of lumber, minus half the hole diameter, plus the thickness of the wall sheathing - or about 1.5" of wood/gyp, minimum. Is that considered adequate depth by NEC? or is this a judgement call?

The plates are cheap and would be relatively easy to install, even everywhere a wire passes through a stud, but I'd rather not worry about bulges in sheathing material in otherwise-flat wall surfaces, which can jump out from certain lighting conditions.

You actually seeing perfect lumber that said bulges aren't a potential issue??

If you want that perfectly flat wall better use steel studs.

 

[hbiss]

You actually seeing perfect lumber that said bulges aren't a potential issue??

If you want that perfectly flat wall better use steel studs.

You won't even get it with steel studs. But it shouldn't be an issue because no wall is perfectly flat and you really don't get a bulge from nail plates anyway. More than likely your beef is going to be with tapers who do sloppy work.

-Hal

 

[808Pants]

Thanks Hal and others. I'm not sure why I didn't get a notification that there had been responses, but I appreciate this help. I just decided a box of plates would indeed be my best approach.

Bulge problem probably won't be one in the long run, but my concern was a bit elevated since I'm not working with gyp, but OSB against the studs in question, so there's no indentation that would relieve some of those framing-plane protrusions/defects (and yes, I'm being very particular about stud-straightness...and they will flex somewhat to follow the plane of the sheathing, which will reduce waviness further. Plates, screw-heads etc can indeed push OSB out noticeably depending on the location. (Next I'll be having to scribe cabinet-backs to fit against a finished wall...)

Dave

 

[hbiss]

Hmmm. I kind of remember that it's prohibited by building codes to apply a combustible material by itself to the inside of habitable wood frame structures, particularly bearing walls. In your case, at least 1/2" sheetrock would be needed under your decorative OSB. Usually doesn't need to be taped, but some places may specify fire taping. (Tape and one coat of mud.) Check out your codes.

-Hal

 

[kwired]

Hmmm. I kind of remember that it's prohibited by building codes to apply a combustible material by itself to the inside of habitable wood frame structures, particularly bearing walls. In your case, at least 1/2" sheetrock would be needed under your decorative OSB. Usually doesn't need to be taped, but some places may specify fire taping. (Tape and one coat of mud.) Check out your codes.

-Hal

probably where those codes are enforced.

What about a log home?

 

[hbiss]

probably where those codes are enforced.

What about a log home?

I believe it's in the IBC.

I believe with a log home, the logs provide enough mass to provide some fire rating. That's a far cry from 1/2" OSB on a wood frame wall.

The house I bought has a ceiling in an upstairs bedroom that is just 1/4" paneling over 1x furring nailed to the joists. They did a really nice job but it is going to have to go. I can recreate it easy enough over sheetrock.

-Hal

 

[PaulMmn]

Hmmm. I kind of remember that it's prohibited by building codes to apply a combustible material by itself to the inside of habitable wood frame structures, particularly bearing walls. In your case, at least 1/2" sheetrock would be needed under your decorative OSB. Usually doesn't need to be taped, but some places may specify fire taping. (Tape and one coat of mud.) Check out your codes.

-Hal

How about all those 'home improvement' shows busily applying 'shiplap' siding to the walls of every room they can find? I don't recall if they do it over drywall or not!

 

[jim dungar]

I believe it's in the IBC

You need to provide a reference.
I believe the IBS only requires it when the wall must be fire rated.

Up here in Wisconsin 1/4" paneling directly over the studs is very common in basements.

 

[wwhitney]

but I'd rather not worry about bulges in sheathing material in otherwise-flat wall surfaces, which can jump out from certain lighting conditions.

You can recess the plates fairly easily using a power planer.

I agree that in Type Vb construction, there is no general requirement for a layer of drywall. There is a requirement for a rated wall if it is < 5' from the property line, and there is a requirement for a thermal barrier (1/2" drywall or 3/4" wood) if there is plastic foam insulation. There may also be a requirement on attached garage walls, not sure about that.

Cheers, Wayne

 

[PaulMmn]

You can recess the plates fairly easily using a power planer.

I agree that in Type Vb construction, there is no general requirement for a layer of drywall. There is a requirement for a rated wall if it is < 5' from the property line, and there is a requirement for a thermal barrier (1/2" drywall or 3/4" wood) if there is plastic foam insulation. There may also be a requirement on attached garage walls, not sure about that.

Cheers, Wayne

I'm reasonably sure that an attached garage must have drywall on the garage side of the studs. Don't know if it has to be fire-rated or not.

 

[hbiss]

Attached garages require 5/8" type FR sheetrock on the interior and fire rated door(s) with closers to the habitable space. Door threshold also must be at least 4" higher than the finished floor of the garage.

You need to provide a reference.

I found the IBC requirements before I made post #12 but I can't find the section now to quote it. :rant:

-Hal

 

[Carultch]

In addition to what the NEC says, I think some common sense comes into play too. I stay away from behind kitchen and bathroom cabinets that will be fastened to the wall (with a potentially unnecessarily long screw) or use nail plates liberally there. A few jobs ago had the heating guy drive a lag bolt thru my wire when mounting a radiator. I would have used nail plates behind them if I had known they were going in. I ask more questions now.

Another suggestion is to photograph the rough-in, after all plumbing and electrical work is complete. This allows the home owner and any other trade concerned, to see specifically where the rough-in work is constructed, and plan in advance if they need to install screws with more than 1.25" of embedment in the stud.

Whether the home owner will have the presence of mind to check this photo / remember where it is, is another matter entirely. But it is a good start to at least have the information available when the house is first turned over for occupancy.