J-box supported by conduit alone

[2wheelinusa]

Anyone have any tricks when wiring buildings with interior metal ribbed siding? I have noticed many times you cannot fasten the 4" box directly to the siding because there is not enough room to offset the conduit coming out of the box before it hits the rib. Even when the ribs are 12" centers there isn't enough room. I have ran conduit from opposite sides out of the box across the ribs and 'floated' the box and that seemed to work well, but I'm not sure if that is code or not. Other ways would be to put a wood block behind the box for a spacer, use offset fittings, or maybe use a box extension and run the conduit into the extension, but all of those are kind of a pain. Any suggestions?

 

[Buck Parrish]

1.5" kindorf is good on the cieling. Perhaps walls , too. I am told caddy is making some straps that will hold the conduit off and below the roof an 1.5" . Some thing about screws hitting the conduits.

 

[celtic]

Some thing about screws hitting the conduits.

300.4(E) might be someplace to look for something about them their screws.

 

[kwired]

I usually cut spacers out of scrap raceway and use longer mounting screws if necessary to space the box out so the KO's are even with the ribs in the sheet metal.

 

[Cow]

A 4" piece of deep strut.

 

[2wheelinusa]

So is it not code to just float the j-box? What if the box is secure with the conduit coming out of the box, but I add a longer screw to get into the sheet metal just to call it 'fastened'. Kindorf strut would be a pain since in this particular shop I'm wiring there are (40) 4" j-boxes on the walls and ceiling. That's a lot of cutting and I don't think it would look very good.

 

[masterinbama]

I mount the boxes in the recesses of the siding and use 90's and kicks out of the top or bottom. If it's roof decking you pretty much have to use strut to space everything out away from the roofing screws.

 

[Rockyd]

So is it not code to just float the j-box? What if...

No you can't "just float" a box. Code says boxes need supported. Only rigid boxes are allowed to be floated - with a bunch addenda that standard verbage to the code.

As far as what if? Countless times we'd all like to get a "one time exception" from various code articles .

Can you cut up a bunch of 2 x4 s' the same length as your box, and attach your box on top of this?

 

[Cow]

So is it not code to just float the j-box? What if the box is secure with the conduit coming out of the box, but I add a longer screw to get into the sheet metal just to call it 'fastened'. Kindorf strut would be a pain since in this particular shop I'm wiring there are (40) 4" j-boxes on the walls and ceiling. That's a lot of cutting and I don't think it would look very good.

Everytime I've needed to use 4 sq boxes on metal interior siding I've always put them on the ribs unless I knew I'd never have to come out the side, then I'd recess them. It'll take you longer to think about what you're going to do, than if you just cut some spacers/strut/2x4, etc real quick on a bandsaw/chopsaw and screwed them up there.

 

[Pierre C Belarge]

See 314.23(E) -which will not permit the use of standard Jboxes to be supported by conduit.


The planning stage of the installation for this type of installation may take more time. Cleverly locating the boxes will help to alleviate the problem you are dealing with.

 

[macmikeman]

Liquid nails, piece of plywood, and some screws.... Whistle the tune of "Money" while you work.

 

[chicagowood]

I'm not sure if your talking about the normal steel roof decking I see but maybe try this box from garvin


http://www.garvinindustries.com/product.asp_Q_parentID_E_388_A_subCatID_E_389_A_prodID_E_1781


hope this might help

Pat

 

[2wheelinusa]

Thanks for your reply's. Some of you have talked about roof decking and roofing screws, which I'm not sure if they apply here. The metal sheets I am talking about are in 3' wide sheets with a 1" rib sticking out every 12" on center. The sheets mount directly to the underside of the rafters to make the ceiling. I use mostly 2 1/8" deep 4" boxes for recepts, switches, and j-boxes for low bay lights, etc. With the ribs being 12" on center, and using a 4in. box, that doesn't leave enough room for offsets from the box. Mounting the boxes directly on the rib as COW mentioned will work, but with the rib only being 1" wide, that doesn't secure the box very well. It tends to 'teeder' very easy, especially if you are plugging into it all the time. I think cutting 2 x 4's as spacers looks like a real hack job because I have tried that before. Even if you paint them to match they are a pain, plus you have to drill a pilot hole or they will split. Maybe I have worn this question out, but I just wanted to make sure everyone knew what kind of metal siding I was talking about. The big question would be, can a box be considered 'supported' if it is mounted 1" off of the siding but is very secure and has a couple long screws going into the siding?? Does the back actually have to be tight against the wall? Thanks again for the reply's.

 

[Cow]

Mounting the boxes directly on the rib as COW mentioned will work, but with the rib only being 1" wide, that doesn't secure the box very well. It tends to 'teeder' very easy, especially if you are plugging into it all the time. The big question would be, can a box be considered 'supported' if it is mounted 1" off of the siding but is very secure and has a couple long screws going into the siding?? Does the back actually have to be tight against the wall?

Help me understand.

You mentioned my idea of straddling a rib with a box would cause it to wobble? But in your next breath, you want to free air a box and use long lags and you think this would wobble less?? Why aren't you straddling the ribs and using long lags?

Like mentioned by other posters, you can't float a 4 square. Use a spacer or mount it against the wall.

 

[kwired]

Like mentioned by other posters, you can't float a 4 square

maybe David Letterman should prove this on his "will it float" segment:grin: