[diymonkey]

I need to mount some junction boxes in my attic for some new wiring. Most junction boxes that I have seen are mounted on the wide face of a joist (location #2 on the image below) but is it acceptable to mount the junction box on "top" of the joist (location #1 on image below) ?

NOTE: This is not a picture of my attic, just a picture i found on google to doodle on.

 

[Bob Mariani]

Yes they are. JB's need to be accessible. This means that you can access them without removing any of the building's structure.

 

[Rivethead]

Bob is correct - they are both acceptable. But, I'd side mount to keep the wires and box below the top of the joists as the wiring is currently run. Note the plates being used to protect the current wiring where it passes theough a joist.

 

[DangerMouse]

but... wouldn't mounting on top make yer wiring job much easier?

DM

 

[Bob Mariani]

but... wouldn't mounting on top make yer wiring job much easier?

DM

You mean keep the wires on top? This only makes house fires easier. Easy is not the determining factor in working with electric... safety is!

 

[DangerMouse]

A: as to jb's, it's ok either way...
B: i'd certainly NOT be worried about fires if the box is on top and wired correctly.
C: the question is about BOXES, not WIRES!
D: if it were me, i'd put the boxes on top simply for the fact if i needed to do anything, the box would not be below the insulation.
no-one said anything about running the wires along the tops of the joists....

DM

 

[dSilanskas]

Come on ladies can't we all just get along:laughing:

 

[Bob Mariani]

yeah take it easy here. We are not attacking anyone, just making it as clear as possible. When mounting on top, it is easy to secure wires not on top of the joists. If you do have wires on top nail a 2 X4 cleat next to them, so they are protected.

 

[Silk]

If you do have wires on top nail a 2 X4 cleat next to them, so they are protected.

Not a code requirement most of the time. It depends on the distance from the scuttle hole and if you have a permanent ladder or stairs to access the attic. If not it is a waste of time and money.

 

[Thurman]

Maybe it's a local code thing, but around here I've never seen the junction boxes in an attic mounted on the side(s) of a ceiling joist. The are always mounted on the top of the joist with the wiring run on the side, some type of securing device (usually a wire staple) securing the wires within twelve inches (12") of the box and per code here-a cover always on the box. That's why it's important to follow NEC and check local codes. Thanks, David

 

[rgsgww]

No way I can do that in mine, like 1.5-2 ft of insulation. Boxes are on top, wires stapled within 12 in of box. Currently I'm fixing some bad wiring, and the bx is shorted somewhere (I did not turn the breaker off, but used a load based continuity checker).

 

[Bob Mariani]

Not a code requirement most of the time. It depends on the distance from the scuttle hole and if you have a permanent ladder or stairs to access the attic. If not it is a waste of time and money.

I did not say it was code. But a good practice and was mentioned as a protection of wires that another posted mentioned.

 

[gma2rjc]

They prefer you keep the boxes on top. This makes it impossible for the home owner to cover and hide the JB with boards.

 

[diymonkey]

thanks everyone for the comments/suggestions. I would rather mount the box on top and then run the wires along the joist (wide side).

I should have pointed this out in my first post, but this is not a picture of my attic. I just grabbed a picture off google so I can doodle on quickly. Regarding the wires in the picture, I thought they were suppose to be run along a 2x4 between the joist (perpendicular). So this is acceptable to have them as shown in the picture?

 

[Bob Mariani]

The ones shown are drilled though the studs and then covered with a nail plate. This is a correct installation.

 

[philS]

J boxes don't just need to be accessible w/o dismantling things. It really helps if they're VISIBLE, which means mounting them up above a level at which some later person might add insulation. Having to crawl on hands and knees feeling your way under a foot of blown in insulation is not fun. If this were my attic I'd add a board from the floor joist up to the rafter and mount the box on that, where it can be seen. Also note that drilling holes in framing members must be done carefully to avoid weakening them.

With roof trusses it's better to not mess with them at all. Just staple wires along side them when going parallel to them. Where you need to cross them you can always run the wires in the tight angles between the truss members, or you can run along the roof. Code says something precise about this but I just stay at least 1 1/2 inches from the top of the roof sheathing to decrease the chance that some future roofer is going to shove a nail into my wires. (Any mistakes in above, please correct me. I'm here also to learn.)

 

[Silk]

The ones shown are drilled though the studs and then covered with a nail plate. This is a correct installation.

Absolutely not! Do not start drilling holes thru your trusses!! You are much better off to run a protection strip at least as thick as the wire alongside the wires if you feel you must protect them although you don't even have to do that by code (with a few exceptions).

 

[Bob Mariani]

Absolutely not! Do not start drilling holes thru your trusses!! You are much better off to run a protection strip at least as thick as the wire alongside the wires if you feel you must protect them although you don't even have to do that by code (with a few exceptions).

I did not think these were trusses. OP said that the wire was already done as is in this picture. So it was inspected. And they look more like 2X6 then 2X4....

Anyway... you would not drill holes in trusses. You can drill holes in ceiling joists that are 2X6 or better.

 

[DangerMouse]

or you can staple them to furring strips mounted to the joists like in this picture. the wires remain accessible above the 15 or so inches of blown cellulose this way.

DM

 

[Scuba_Dave]

I never drill thru joists unless they are larger
Some 2x6's (like my 2nd floor) are already beyond the span calcs
Drilling a hole in them only weakens them further
I take each instance & verify what the joists are & how far they are spanning
I prefer running a furring strip/2x3/2x4 across the joists & fasten to that

Also take into account if the attic can ever be made living space

In the 1st picture (I know its not yours) I would have run past the ends of ths joists (you can see the cut ends), the down to the bay & down the side of the joist. Slightly more wire but leaves the joists intact if they are slightly "undersized" already

That's one heck of an open un-insulated space DM !!