ICFs and Electrical Code
Last Post 17 Oct 2008 10:33 AM by ICFconstruction. 9 Replies.
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DABA78User is Offline
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16 Oct 2008 08:43 PM
Hello!

I have been considering purchasing an ICF home on which construction was started, but is not yet completely finished.

Actually, the exterior is completed, and indoor framing done, and some electrical wiring and drywall have been completed.

The local municipal inspector took a look at it the other day, and said that electrical code requires a staple to secure the wiring within a certain number of inches from an electrical outlet box (plastic electrical boxes were used, if that matters). Don't remember the exact distance...maybe within 12" from boxes. He said that the drywall around the boxes will have to be removed so that the boxes can be inspected (wouldn't be too tough to remove drywall, as it is screwed in place, and joints haven't been finished yet).

But I'm wondering this...in the case of ICF walls, what would the wire be stapled to? Nothing but foam and concrete there.

Does anyone know what the National Electrical Code specifies for wiring in ICF walls?


James EggertUser is Offline
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16 Oct 2008 08:55 PM
I guess the question is WHY was drywall installed before the rough electrical was approved? The use of a staple is somewhat of an interpretation issue, as the staple doesn't have any pull-out resistance, but once the staple is placed it DOES hold the wire back the required 1 1/4 from the face of the wall(stud).

We many times simply placed a dab of spray foam at spaced intervals to hold the wire in place.

You should remove a few sections of the rock and then discuss with the inspector what he(she) feels is a safe compromise! The wire once installed in the foam groove generally stays there....unless the groove was done with a sawzall by some uncaring/unknowing installer!
Take Care
Jim

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"Not So Big" Design Proponent
DABA78User is Offline
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16 Oct 2008 09:28 PM
Thanks for the quick response, Jim.

I think that the drywall was installed before electrical inspection was done  because the house is located in a semi-rural setting, and the guy who built it possibly didn't realize that an inspection would be required.

I'm really undecided about the house...I am really sold on ICFs, and would like to live in one. The particular house I'm looking at was built by a guy with some construction experience, but he's no longer in the area, and of course I can't tell if everything was done as it should have been during the building process.

For example, the inspector also said that it appears that no waterproofing membrane was installed on the ICF basement foundation walls, as the area of blocks with the brick ledge is partially exposed. He said that it appears that some type of board was used in place of the membrane at some point below the brick ledge.

The inspector also heard from a local concrete truck driver (who was on the jobsite) that there was a blowout during the pour (which, if I understand correctly, is not necessarily a terrible thing), and also that a section of wall is bowed.

So, I'm trying to sort out whether these are really serious problems with the house, or if the inspector just isn't very familiar with ICF construction (as far as I know, there is only one other ICF home in the county).

The house still has no plumbing, HVAC, etc., which is not necessarily a bad thing, because I could make some decisions in those areas.
ICFconstructionUser is Offline
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16 Oct 2008 09:31 PM
My understanding, and what has every time passed electrical inspection, is securing the wiring near each box and at the required interval. Urathane foam has always been enough, we also use the foam to secure the boxes.
Brad Kvanbek - ICFconstruction.net
DABA78User is Offline
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16 Oct 2008 09:55 PM
Thanks for the info, ICFconstruction. Sounds like a good solution.

Is urethane foam the expandable stuff that is dispensed from spray cans?
dmaceldUser is Offline
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16 Oct 2008 11:08 PM
The NEC doesn't require the cable to be stapled. It requires it to be supported. Max 54" center to center, such as staples, and within 12" of a box with cable clamps, or 8" for boxes without cable clamps. The cable also has to have 1 1/4" space between it and the backside of the drywall or must be protected by metal. A tight groove cut in the ICF foam with a depth near to the concrete provides all of this. The NEC doesn't specifically address ICF.

As to foam in spray cans. If your are going to do a lot of foaming you will want to buy a foam gun and get the foam in cans that attaches to the gun. You should be able to find it at tool and material dealers that cater to the construction trades. Any ICF block dealer will have it also. Commercial foam costs maybe only about 20% as much as the spray can stuff from retailers. I bought 30 cans of expired date blue can foam from Lowes before I started my ICF house at half price for $3 a can. Great bargain, or so I thought. For only about 3 to 4 times that amount per can I bought foam from my block supplier, and a local tool company, that probably equaled 10 times the output per can!
Even a retired engineer can build a house successfully w/ GBT help!
DABA78User is Offline
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17 Oct 2008 12:59 AM
Thanks for the info, dmaceld.

Since the code calls for the wire to be supported, being pressed snugly into a groove certainly seems like it would qualify, as long as the groove is deep enough behind the drywall.

I wonder if, after the electrical wiring has been inspected, it would be a good idea to cover the entire length of the groove which contains the run of wire. Seems like it would re-establish any insulation that might have been lost when the grooves were cut down to concrete.

Thanks also for the tip about the foam in cans.
Cattail BillUser is Offline
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17 Oct 2008 08:31 AM
We have had several instances where the electrical inspector would not approve the foam as good enough so we have converted to using a small finish nail.

We simply use a needle nose pliers and install the nail by pushing against the wire and giving it a twist so it will lock into the foam, the inspectors feel good about this because it is an actuall mechanicle fastner.

We do use foam when ever possible as it is faster but if you have an inspector who requires a mechanicle fastner ask the inspector if the finish nail system will be satisfactory.
dmaceldUser is Offline
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17 Oct 2008 09:31 AM
Posted By DABA78 on 10/17/2008 12:59 AM

I wonder if, after the electrical wiring has been inspected, it would be a good idea to cover the entire length of the groove which contains the run of wire. Seems like it would re-establish any insulation that might have been lost when the grooves were cut down to concrete.

I wouldn't (didn't) bother. The area of wall so exposed is a tiny percentage of the wall area. I'm not sure you'd recover the cost of the relatively expensive foam you would use. Plus it's a pain to put it in and then shave off what expands out of the groove. And, although it's probably more theoretical than real, filling in the groove blocks off all avenue for heat to escape the cable. Ampacity ratings for electric cable are impacted by temperature. Trap whatever little heat is generated by the power going through and you raise the temperature of the cable. At least this sounds like a good excuse to me avoid that bit of work!!! :-)


Even a retired engineer can build a house successfully w/ GBT help!
ICFconstructionUser is Offline
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17 Oct 2008 10:33 AM
I also don't fill the entire grove, due to possible heat build up.
Brad Kvanbek - ICFconstruction.net
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