Quick question about wiring on an exterior wall

zachslcDecember 9, 2007

I have the black and decker book but it does not quite answer my question and the NEC is just a little too dense for my amateur knowledge. I am pretty confident with interior wiring, but I have a question about materials and code compliance on an exterior wall. On the south side of my house I want to add a light fixture and a GFCI. The walls are brick and concrete (1920s construction) I am going to cut into the brick to mount the (metal?) boxes, but what I am not sure about is what I have to do to get the romex (which I can use, right?) o the boxes. From the back of the boxes to the inside of the wall there will be about 3 inches. Do I need a conduit here? In short, my question is what do i need to do to get the wire from the inside to the outside? The boxes on the outside will be well about the ground--6 or 7 feet and under a roof overhang.

Can I just use the regular metal or PVC outdoor boxes, obviously with appropriate covers and outdoor lights?

Can I use regular romex?

What kind of conduit and/or seal do I need to connect to the boxes?

Thanks in advance for your help.

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arichard21

you could save yourself some trouble and use a surface mount exterior box, then just drill through for your wire.

if i am not mistaken, you should use uf-b because it would be classified as a damp location.

    Bookmark   December 9, 2007 at 3:39PM
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zachslc

Thanks, but I am pretty set on not using surface mount boxes. I want it to look clean. It is easy enough to cut out the brick.

Do you know if I need conduit?

    Bookmark   December 9, 2007 at 5:37PM
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cobraguy

"From the back of the boxes to the inside of the wall there will be about 3 inches"

Of what? More brick? Concrete? Insulation? Normally, if you run cable from inside the house to receptacles on the outside wall, NM is used. NM isn't supposed to be in conduit. However, there are some exceptions I've seen mentioned here.

    Bookmark   December 10, 2007 at 10:27AM
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zachslc

3 inches of basically mortar and plaster. The walls are solid brick with concrete/mortar on the inside then plaster. There is no hollow space.

So if I use NM what kind of seal do I need to use between the wire and the box?

Thanks for being patient with me.

    Bookmark   December 10, 2007 at 11:46AM
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bigbird_1

Running NM from the interior of the house through the brick/stucco/mortar/concrete/volcanic pumice/whatever is fine. You'll need a box connector on the rear of the box where the NM enters. You can put a bead of silicone along the rear top of the box if you want. I'd fill the hole in the wall at the rear of the box with good old Duxseal, the same stuff you'd use on service entrance.

    Bookmark   December 10, 2007 at 12:07PM
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