bidding and wiring a concrete house

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warriorelectrician

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I have a contractor I want to get, and my first trial run with him is a concrete house, with 4" styrofoam walls, my questions are: what is a legal way of securing wires and boxes. Do I just cut channels in the styrofoam and push the romex in or is there a better way of doing this. My next question is how do I bid this so I don't lose money on the job
 
warriorelectrician said:
I have a contractor I want to get, and my first trial run with him is a concrete house, with 4" styrofoam walls, my questions are: what is a legal way of securing wires and boxes. Do I just cut channels in the styrofoam and push the romex in or is there a better way of doing this. My next question is how do I bid this so I don't lose money on the job
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Thats the way I have seen them do it on This Old House. They have a tool that is a loop of hot wire they use to cut the channels.
 
warriorelectrician said:
My next question is how do I bid this so I don't lose money on the job
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Eeek. I hate bidding work I've never done before. I try, with all my power, to get odd work like this on a time and material basis. This way, I can keep careful track of my productivity so that I can give an honest bid on the next one that comes down the pike.
 
We are currently rough-wiring an ARXX house as you have described.

We use an electric chainsaw to cut out the holes for the boxes and grooves for the wire.

We have discovered that your standard Carlon B-118B plastic nail-up box fits nicely into the foam, with 1/2" protruding for flush finish with the drywall. You can fasten it directly to one of the vertical plastic "studs" present in the ARXX panels. We have also cut off the nails from B-118A boxes, and set them snug into the foam, and then fastened the boxes tight with some Great Stuf expanding spray foam.

As for "supporting" the romex in the foam grooves, you have to use a blunt tool to push it in all the way, and it's held in very tight without any further need for staples or straps. Again, you can seal the grooves with some more of that Great Stuf expanding spray foam. No nail plates are needed, as the wire is more than 2" deep from the wall surface.

As for pricing, figure your rough-in time to be 3 to 4 times longer than your normal install.
 
You should probably check with your inspector on what is acceptable supports. Here we cannot use the foam to hold anything. When I have done these I attached the box (used a 4sq) and the romex (using cable ties) to the concrete. In my case the foam was under 2.5 inches thick.
 
macmikeman said:
Just curious, but how do you secure within 12" of a box with this stuff?
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On TOH I think they used cans of foam to make the boxes stay in place. I did not really notice how they secured the Romex. I would have to bet that having the cable in some foam is probably more secure than a staple. That stuff is very strong once it sets.
 
We have done 15 to 20 basements with the 4" foam and found a hot knife for candles works the best.For boxes we use front fiber nail ons,2,3, an 4 gangs we use metal 4sg and mud rings mounted on 16" brackets.Use the plastic strip as your stud,self tapping sheet rock screws seem to work the best.Sum of the forms have a metal strip behind the plastic.We run every thing up and down, stuff your wire in the groove and foam everything when your done.It's not as fast as wood but not that bad.We have made sum good $$ doing them(after the first 1 or 2 learning curve).The PRO 1 hot knife seems to hold up the best,you can get about 4 houses out of it before the handle brakes.
 
I did one of these about 2 years ago it was a 3 story house.
Inspector would not let us use expanding foam to support boxes or NM cable.

we used a carlon box B1188-UPC with a plastic bracket on the side with a 1/4 shim behind braket to bring box flush with drywall since there was 1/4 layer of foam over top of plastic studs.

for supporting the NM cable we used arlington cable stackers that were mounted to concrete with plastic anchors this was just at the box location other wise we ran NM cable thru pre made slots in plastic studs,

an electric chain saw was used to cut foam.
we drilled a hole in the bar of the chain saw the same depth as the foam less 1/4 inch so you dont hit any hi spots in concrete. installed a short peice of 3/8 allthread to act as depth guage.

figure 3-5 times normal cost of wood frame house. I will never wire a foam house again. I did make good money but what a Hassle.

Good Luck keep me posted on your out come.
 
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