Mains wiring question (USA)

A 1-story, flat-roof house (no basement) in California is going to be re-covered, so it's a prime time to do some electrical upgrades.

The local building inspector says that romex cable run on the roof (before foam insulation is put on) must be covered by sheet metal stapled over it to protect from nail incursion (yes, he knows this is a *foam* roof, no shingles, etc., but no matter).

I've asked electrical supply wholesalers about this but they have no product such as this.

Is this something an electrical supplier would have? Or is just a roll of sheet metal stock what's called for?

Thanks.

Reply to
Bob E.
Loading thread data ...

You might be able to use armored cable, the MX or whatever stuff. It's not very expensive.

John

Reply to
John Larkin

You might ask him how sheet metal, which staples can penetrate, will protect the romex from nails. The real requirement may be that you will need to run it in steel conduit. Art

Reply to
Artemus

There is no logic to the declarations of building inspectors. He says if we choose to use romex (our option), we must cover it with metal strips wherever it is exposed.

Another option is to use armored (MX) cable or EMT conduit. Romex seems the simplest if we can find a simple metal strap to cover it.

Thanks.

Reply to
Bob E.

For actual protection you want EMT or armored cable. While this roof is a foam roof, there's no telling what the next roofing job (quite possibly not done by you) will put over it...

To make the inspector happy you ask the inspector what the inspector wants to see. As described by you, a 50 foot roll (or as many as you need) of 4-6" aluminum flashing ("sheet metal") would apparently suit the inspector, while providing no protection to speak of (and the delightful possibility that you manage to staple into the cable while trying to staple the sheet metal over the cable). Of course, if you do that without getting a specific clearance from the inspector that this is what he wants to see, he might come back and indicate that he actually wanted galvanized steel, not aluminum, and make you rip it all up. At which point using EMT looks a whole lot easier, as well as more effective.

Reply to
Ecnerwal

Where some types of wiring is near the edge of a stud and may be hit by a drywall screw the wiring needs to be protected by a 1/16" steel plate. I suggest you ask the inspector how heavy the "sheet metal" has to be. I don't know of a standard electrical item for the protection you need. I would ask at a company that makes ventilating ducts.

Reply to
bud--

EMT (electrical metallic tubing) is not considered protection for wiring, just tubing.

Use some square metal roof conduit designed for the job. It will probably stick up and not have anything stapled on top of it, Or put the wiring under the roof sheeting.

For actual protection you want EMT or armored cable. While this roof is a foam roof, there's no telling what the next roofing job (quite possibly not done by you) will put over it...

To make the inspector happy you ask the inspector what the inspector wants to see. As described by you, a 50 foot roll (or as many as you need) of 4-6" aluminum flashing ("sheet metal") would apparently suit the inspector, while providing no protection to speak of (and the delightful possibility that you manage to staple into the cable while trying to staple the sheet metal over the cable). Of course, if you do that without getting a specific clearance from the inspector that this is what he wants to see, he might come back and indicate that he actually wanted galvanized steel, not aluminum, and make you rip it all up. At which point using EMT looks a whole lot easier, as well as more effective.

Reply to
Josepi

You would buy the metal stock from the roofers. They use it to make up flashing and other transistions.

Charlie

Reply to
Charlie E.

The inspector is not crazy, just following the arcane rules like the good droid he is. You're looking for something like these:

formatting link
They are typically used to protect cables and copper water pipes from drywall nails/screws. Probably find them at the local mega hardware store for not much money -- 19 cents each at the link above.

Like a few others, I'd vote for whatever type of conduit rocks your boat unless you're sure there will never again be the need for wiring mods.

Ken

Reply to
Ken Lowe

From the 2008 edition of the NEC:

300.4 Protection Against Physical Damage ...

(A) Cables and Raceways Through Wood Members.

(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 (1¼ 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.

Exception No. 1: Steel plates shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid non-metallic conduit, or electrical metallic tubing.

Exception No. 2: A listed and marked steel plate less than 1.6 mm (1/16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted.

There is no provision to exempt type AC cable ("bx") from the nail-plate protection requirements.

Reply to
Rich.

It is a foam roof now, but what might it be in the future? Perhaps the inspector (and the local code) is looking out for the next guy who owns the property?

Why not just use outdoor RIGID conduit? Is there a huge difference is price? More than a couple hundred?? At least that way, if you ever had to replace or up-size those conductors, you could just pull it. Or course, I don't know if rigit conduit surrounded by foam would have any thermal or other deleterious effects on the foam. I somewhat doubt it. But worth checking if you go that route.

-mpm

-mpm

Reply to
mpm

Wow. Foam roof and EMT vs romex, i would take a really serious look at EMT (and perhaps simple conductors instead of romex).

Reply to
JosephKK

Actually, thinking about what he is doing, i would be real tempted to go with something solider, like rigid, instead of EMT...

Reply to
Charlie E.

Reply to
John Fields

Rigid Metallic Tubing is different from EMT. Rigid is threaded and heavier.

tm

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---

Reply to
tm

EMT is sometimes called "thin wall" to differentiate it from "rigid", which is similar to iron pipe in dimensions and wall thickness.

Reply to
VWWall

Hi John, Not really. Rigid is a lot thicker and harder to work with than EMT, but it lasts literally forever if not physically damaged. EMT will dent if you look at it sideways... ;-)

Charlie

Reply to
Charlie E.

I doubt seriously that his application would outstrip the strength of regular EMT. Just plan and install it AND the 'strips' correctly.

Reply to
life imitates life

What? "Cheap Chinese" EMT and Superman looking at it?

Reply to
life imitates life

No it is not.

rigid is like water pipe..

Reply to
Jamie

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.