Plastic vs. metal j-box?

[BMacky]

I am doing the electrical for an owner-builder run home project. The owner consults with me on something then I get feedback down the road (when someone with a different answer pops up) as to the validity of my input. To add to my frustration it's been a long project (May '08 to present).

So here's the question and I will try to qualify it: I guess we are talking fire rating here. What would be a better choice if you were very fire-conscious (paranoid, perhaps) and wanted the most robust materials in your construction, metal or plastic boxes?

I installed a combination of metal and plastic boxes throughout the building, depending on the application. The owner made a point of telling me that "Joe" told her that "metal boxes are far superioir" to plastic. Well, A 2-hr fire rating is a 2-hr fire rating. What else are we talking about here? An aircraft landing on top of the place?

Anyone have any feedback. I trust my peers have some sane replies. And hey, "Who cares" is as valid an answer as any at this point.

Thanks!

Bob

 

[Sierrasparky]

Well of course metal boxes are a better product. They are more robust. Metal boxes don't crack or break.they are stronger. However there is no comparison to the cheap price of the plastic variety. But I am sure you know that.

 

[bobsherwood]

If you want the best, metal. But, there is NOTHING wrong with plastic boxes in a home.

 

[JFletcher]

imo, metal boxes and mudrings, wrapped with firestop putty pads, are the best for robustness, fire resistance and lowered sound transmission.

If they are *super* fire paranoid, they could always have a FA and sprinkler systems installed - i.e., like a commercial building.

 

[BMacky]

Thanks, but do you happen to know if the fire rating is longer? It seems the listing is 2 hrs no matter what, plastic or metal, but maybe they do last longer. I was told the steel heats up and can conduct way more heat, so it breaks down the surrounding materials faster (gyp board, whatever), which makes sense.

 

[ItsHot]

stripped

stripped

Screw holes are more likely to become stripped on plastic boxes.

 

[macmikeman]

Prior to plastic wrap like Tyvek on the exterior walls, metal boxes used on exterior walls in my state were real likely to rust out after not too many years. The old way to wrap a house was to use roofing paper instead of Tyvek. Has nothing to do with fire rating, but in any case the metal ones did not hold up as well as the plastic ones in these older houses on the exterior walls.

 

[celtic]

Plastic boxes do not conduct electricity
Plastic boxes do not rust
Plastic boxes do not require EGC
Plastic boxes are lighter than their metal counterparts
Plastic boxes are cheaper to buy
Plastic boxes will outlast the building.



Brought to you by the Plastic box institute
:grin:

 

[JFletcher]

Plastic boxes do not conduct electricity
Plastic boxes do not rust
Plastic boxes do not require EGC
Plastic boxes are lighter than their metal counterparts
Plastic boxes are cheaper to buy
Plastic boxes will outlast the building.



Brought to you by the Plastic box institute
:grin:

:grin:

Metal boxes do not bend or warp
Metal boxes do not crack (like fiberglass, not plastic)
Metal boxes do not have to be moved if the wall depth changes (or I screwed up reading the bps on wall finishes)
Metal boxes are more bad-sheetrock-installer resistant (biggest plus imo)
Metal boxes are available in deeper depths
Metal boxes can be mounted on stud braces w/o drilling
Metal boxes weigh more, and thus they build stronger muscles... for my helper
Metal boxes do not have nails sticking out of them, waiting to impale my foot.

Metal FTW! Buy better: buy metal!!

Putting playing Devil's Advocate aside for the moment, metal and plastic have their pros and cons.

 

[quogueelectric]

:grin:

Metal boxes do not bend or warp
Metal boxes do not crack (like fiberglass, not plastic)
Metal boxes do not have to be moved if the wall depth changes (or I screwed up reading the bps on wall finishes)
Metal boxes are more bad-sheetrock-installer resistant (biggest plus imo)
Metal boxes are available in deeper depths
Metal boxes can be mounted on stud braces w/o drilling
Metal boxes weigh more, and thus they build stronger muscles... for my helper
Metal boxes do not have nails sticking out of them, waiting to impale my foot.

Metal FTW! Buy better: buy metal!!

Putting playing Devil's Advocate aside for the moment, metal and plastic have their pros and cons.

Metal boxes in resi are for insurance that the cheapest electrician that doesnt know what they are doing will less likely start a fire with a metal box. Yet the underlying problem would be the inadequate electrician.

 

[macmikeman]

:grin:


Metal boxes do not have to be moved if the wall depth changes (or I screwed up reading the bps on wall finishes)



Metal boxes do not have nails sticking out of them, waiting to impale my foot.

.

I take friendly umbridge at those statements:grin: A metal box set back from a combustable surface or a non combustable surface more than 1/4" is no more allowable than a plastic box.

They still sell metal nail on boxes.

 

[JFletcher]

I take friendly umbridge at those statements:grin: A metal box set back from a combustable surface or a non combustable surface more than 1/4" is no more allowable than a plastic box.

They still sell metal nail on boxes.

I was thinking more 4 square boxes than the nail-on 2x4 variety. GC decides to change all shear walls to the opposite side of the wall, or eliminate/add resilient channel, or add/remove sheetock, it's no big deal to me: I move/change mud rings. With nail-on 2x4 boxes (metal or plastic), I've got to rebox the entire building, so that, as you correctly point out, the box faces are basically flush with the wall finish. That has happened more times than I care to think about.

My opinions re: metal boxes are more (solely) based on commercial (hotel) work, not resi.

"Friendly umbridge?" is that a HP reference? :-?:grin:

 

[nakulak]

I like the big heavy 300 lb explosion proof boxes. I think you should sell those to the lady, and pipe the whole house in rigid. that should make her very happy

 

[A/A Fuel GTX]

IMO....Allied Molded fiberglass boxes are the way to go. Besides, 99% of the metal boxes I encounter in residential situations are not properly bonded to the EGC.

 

[macmikeman]

IMO....Allied Molded fiberglass boxes are the way to go. Besides, 99% of the metal boxes I encounter in residential situations are not properly bonded to the EGC.

Must be me and my wacky hammering, but I got a penchant for busting those when I swing wild at that nail.... For the same reason I try not to buy bakalite boxes from Union either.

 

[byourdesky]

Screw holes are more likely to become stripped on plastic boxes.

The beauty of plastic boxes is you can always "use a bigger screw"

 

[quogueelectric]

The beauty of plastic boxes is you can always "use a bigger screw"

Arlington makes a nice line.

 

[cowboyjwc]

I do enjoy this forum as it opens my eyes some times. I've never really had a metal/plastic preference since they both have their place.

But as I'm walking a big remodel job yesterday I came upon a metal box that was all bent to heck and gone and realized that for every opinion, there is another opinion that's just the opposite.

 

[zappy]

How about for fire rated walls like in a garage. Doesn't the ceiling box for yhe garage door opener need to be metal or bakelite?

 

[augie47]

I like the big heavy 300 lb explosion proof boxes. I think you should sell those to the lady, and pipe the whole house in rigid. that should make her very happy

That was along my line of thought. Rigid with malleable FS boxes..