Securing NM cable to strapped masonry wall

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Old 04-09-13, 06:17 PM
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Securing NM cable to strapped masonry wall

Can anyone suggest a way of securing cable to masonry walls with embedded furring strips/strapping? The triple brick walls have a parge coat on the interior side and wood strips are embedded horizontally. 1/2 inch strapping is nailed to the strips vertically every 16 inches. The plaster and lathe are removed. I know that there is a product by 3M that is secured to the strapping and that it keeps the cable 1 1/4" away to the side of the strapping. What about the issue of keeping the the cable 1 1/4 back from the drywall? I am adding another 1/2" of vertical strapping over top the original 1/2 inch strapping. This will give me 1" between the embedded strips and the drywall. I assume that I will have to use protective metal plates, but how many? And all the wall up the wall? Also, would conduit be an option?
 
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Old 04-09-13, 06:36 PM
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Ah.....you posted a pic. Excellent. I was drawing in the mean time.

In my illustration the red are your horizontal pieces of wood in the masonry.
The blue is the furring you will be adding.
If you were to run the wire in the center of the furring area you would move the wire away from the furring......which is where the sheetrock would be fastened.

What are you doing for boxes ?
 
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Old 04-09-13, 06:37 PM
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It is not required to keep the cable 1 1/4" away from the drywall, just 1 1/4" away from the nailing/screwing face of the framing member. It is assumed that any fasteners installed, will be attached to the framing, not just to the drywall.
 
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Old 04-09-13, 07:39 PM
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You could use a product like this one.

Non Metallic Fittings And Supports | Cable Standoffs
 
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Old 04-10-13, 04:36 PM
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PJ, you're getting the picture. I forgot to mention those two vertical lengths right next to the wire. There is no original strapping underneath those. The intent was to have nailing plates spanning across those two vertical strips all the way up, thus protecting the wire. Spray foam insulation would keep the cable from moving in that small space. Also, the drywall not be fastened to those strips. If I were to have gone through installing the wire this way, would the inspector have an issue with this since I wouldn't be using those 2 vertical strips for drywall screws? For boxes, I'm fastening horizontal furring strips right above and below the boxes so the box ears can be fastened to them. These horizontal strips are fastened to the original vertical furring strips. Since I need 1" of wall to make up for the original lathe and plaster, these horizontal strips placed over top of the original furring strips do not interfere with the drywall. The drywall goes over top of the horizontal strips. Using 2" deep boxes is tricky going by the box fill table. I can fit a 2.5" box if I remove the parge coat. Now that I think about, I'm just going start using 4" square boxes with plaster rings.
Now that I understand that the cable doesn't have to be kept back from the drywall, all I have to do is use cable standoffs. Piece of cake. Now I can pass this info on to others. Thanks guys.
 
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Old 04-10-13, 06:32 PM
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Also, the drywall not be fastened to those strips. If I were to have gone through installing the wire this way, would the inspector have an issue with this since I wouldn't be using those 2 vertical strips for drywall screws?
It does not matter whether or not you are going to use the strips to attach the drywall, it is more CAN you use the strips to hang the drywall, or anything else. If the framing is in contact with the drywall, it is assumed that it is a nailing face and the cable needs to be kept 1 1/4" away.

Now that I think about, I'm just going start using 4" square boxes with plaster rings.
That is a good plan.
 
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