My barn has trusses 4' on center, with 2X4's running perpendicular on 4' centers, that create 4' squares. I'm going to install octagon boxes in the center of some of these squares, with lamp holders and LED light bubs. I'm using 1/2" EMT. MY question is, Can the EMT support those boxes on their own, or do I need to support the boxes as well? Thanks. John.

 

Conduit can not be used to support boxes, they need to have their own support.

I would also not recommend using octagon boxes. I would use 4" x 4" boxes with square to round mud rings. Square boxes have more room and more knock outs available on each side.

 

Can I use empty conduit as a support?

 

If the conduit is supported independly of the box I guess you could,why not use a piece of Uni Strut ?

 

I would suggest a 2x2 horizontal wood member to span the 4' space and support the light fixture.

An alternative is a vertical chain or rod or similar support attached to the sheathing or ceiling above, provided that the fasteners can hold securely without going through roofing material on the other side of sheathing.

I do not think that an empty piece of 1/2" EMT mounted horizontally would adequately support a light fixture in the middle of a 4' span.

 

Why has no one suggested Unistrut? Isn't this what it is made for?

 

I would say yes, and no, depending how you use it. If you just used the empty conduit connected to the box with an EMT connector, I would say no. If you layed the conduit horizontal across the back of the box and attached the box tot he conduit with some self tappers, or attached some conduit minis to the box with some 1/4 - 20 screws and nuts and then clamped it to the conduit, I would say that is OK. I would say use 3/4" conduit or larger, and of course, the conduit would need to be attached on both ends.

See post #4

Unistrut is great but at $17 a 10' stick it is an expensive way to go. 2x2's are cheap.

 

I completely agree with Tolyn on all counts!

 

Thanks guys for the help. I think I'm going to go with the 2X2's. The uni strut is nice, but the amount that I would need, is cost prohibitive. John.

 

2x2's spanning 4' are going to be borderline supportive in that they will tend to bow and warp. I would go ahead and install 2x4 lumber on edge fastened between the adjoining supports.

 

Ray check post #4,great product although a bit expensive.
Geo

 

Sorry Geo. skimmed the thread to fast and missed your post. I've been a fan of Unistrut ever since I built a roof rack for my van. Cost way less than a factory rack and so I tend to forget it is relatively expensive.

Here I wouldn't even consider 2x2 because all they sell is #1 or better at the same or greater than the cost per foot of stud grade 2x4s. If I want 2x2s I can just rip 2x4s and they cost half as much.

 

An even better idea. 2x4's it is. Thanks guys.