Rebar in Tilt-up concrete walls

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JMC01

Member
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work mostly
Is the re-bar in a tilt-up wall considered as an electrode as described in 252.52 if the wall is sitting on a concrete footing. (No rebar tied between the footing and the wall) ? The bottom of the wall is below finished grade.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Welcome to the forum.:)

The vertical portion of a foundation wall can qualify as a concrete encased electrode if at least 20' of rebar is encased and the foundation is in direct contact with the earth.

Check out 250.52(A)(3) 2008 NEC.

Chris
 

kwired

Electron manager
Location
NE Nebraska
If there is a waterproofing sealant applied to the concrete then it is likely not in direct contact with the earth - the sealant is.
 

dana1028

Senior Member
Welcome to the forum.:)

The vertical portion of a foundation wall can qualify as a concrete encased electrode if at least 20' of rebar is encased and the foundation is in direct contact with the earth.

Check out 250.52(A)(3) 2008 NEC.

Chris

Agreed - however, a tilt-up wall is not a foundation; and I believe the OP indicated there is not [rebar] connection between the tilt-up and the foundation. It is commom for these walls to just sit in a key way designed in the foundation.
 

mcclary's electrical

Senior Member
Location
VA
Is the re-bar in a tilt-up wall considered as an electrode as described in 252.52 if the wall is sitting on a concrete footing. (No rebar tied between the footing and the wall) ? The bottom of the wall is below finished grade.



That would not be considered an electrode. However, I had an indoor pool next to a similar wall, so I had to bond the steel in the wall, as well as the floor. But it would not be required in most cases
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Agreed - however, a tilt-up wall is not a foundation; and I believe the OP indicated there is not [rebar] connection between the tilt-up and the foundation. It is commom for these walls to just sit in a key way designed in the foundation.

I see no reason that a tilt up wall can't be a foundation.

The original poster said the tilt up wall was buried in the earth. IMHO that means that it could very well be being used as a foundation and could be used as a CEE.

Chris
 

hurk27

Senior Member
I see no reason that a tilt up wall can't be a foundation.

The original poster said the tilt up wall was buried in the earth. IMHO that means that it could very well be being used as a foundation and could be used as a CEE.

Chris


H'mm I read the OP as saying:
the wall is sitting on a concrete footing
?

And the code states the CCE has to be in the footing if there is one?

(3) Concrete-Encased Electrode. An electrode encased
by at least 50 mm (2 in.) of concrete, located horizontally
near the bottom
or vertically, and within that portion of a
concrete foundation or footing that is in direct contact with
the earth,
consisting of at least 6.0 m (20 ft) of one or more
bare or zinc galvanized or other electrically conductive
coated steel reinforcing bars or rods of not less than 13 mm
(1⁄2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of
bare copper conductor not smaller than 4 AWG. Reinforcing
bars shall be permitted to be bonded together by the
usual steel tie wires or other effective means. Where multiple
concrete-encased electrodes are present at a building
or structure, it shall be permissible to bond only one into
the grounding electrode system.
 
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dana1028

Senior Member
The OP said the tilt up was below grade....he didn't said it was buried. Even if it were under earth, that wall would have to be considered a component of the foundation...that would be a design issue reflected on the plans.

As an aside I have inspected similar types of walls that were not touching the earth; they had a retaining wall with French drains separating the earth from the actual vertical structure...small air gap between the two.
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
Is the re-bar in a tilt-up wall considered as an electrode as described in 252.52 if the wall is sitting on a concrete footing. (No rebar tied between the footing and the wall) ? The bottom of the wall is below finished grade.

At first I was going to give a blanket no. But after reading 250.52(A)(3) I would say yes IF it met the 20' rule.

Remember 1/2" rebar not 3/8".

SO Yes, but now read the last line: "Where mulitple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond ONLY ONE into the grounding electrode system."

This could be good if you forgot the footer "grounding" but only if it (the wall) met ALL the requirements in 250.52(A)(3).
 

JMC01

Member
Location
work mostly
Thanks Mike.

The building electrical contractor not only forgot the rebar for the slab and footings. All components with the exception of a ground ring were available. He didn't bond any of them together and I am argueing that he has not properly installed a grounding electrode system. He has only installed 1 driven rod with a gec from it to the ground bus of the switchgear and argues that is all that is required by code.
 

eprice

Senior Member
Location
Utah
Thanks Mike.

The building electrical contractor not only forgot the rebar for the slab and footings. All components with the exception of a ground ring were available. He didn't bond any of them together and I am argueing that he has not properly installed a grounding electrode system. He has only installed 1 driven rod with a gec from it to the ground bus of the switchgear and argues that is all that is required by code.

The rebar in the footings is present. If it determined that the rebar in the tilt-up walls qualifies as a CEE, then it too is present. 250.50 requires electrodes that are present to be used. As mentioned above, the last sentence of 250.52(A)(3) allows the use of only one of the CEE's, but he is required to use at least one.
 

cripple

Senior Member
Rebar in Tilt-up concrete walls

250.52(A)(3) defines s concrete electrode as ?an electrode encased by at least 50 mm (2 in.) of concrete, located horizontally near the bottom or vertically, and within that portion of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (1/2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG.?
To qualify as a grounding electrode the wall would have to be part of the footing or foundation. The tilt up in my opine is as sentenced just a wall and could not be considered as meeting 250.52(A)(3).
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
250.52(A)(3) defines s concrete electrode as ?an electrode encased by at least 50 mm (2 in.) of concrete, located horizontally near the bottom or vertically, and within that portion of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (1/2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG.?
To qualify as a grounding electrode the wall would have to be part of the footing or foundation. The tilt up in my opine is as sentenced just a wall and could not be considered as meeting 250.52(A)(3).

Here is a picture of a foundation wall: http://www.concretenetwork.com/photo-gallery/site_26/concretenetwork-com_6179/

I think all three sections in the picture qualify.

If you have the commentary read this in 250.52(A)(3): "**** that individually qualify ****"
And look at the exhibit 250.23.
 

cripple

Senior Member
Here is a picture of a foundation wall: http://www.concretenetwork.com/photo-gallery/site_26/concretenetwork-com_6179/

I think all three sections in the picture qualify.

If you have the commentary read this in 250.52(A)(3): "**** that individually qualify ****"
And look at the exhibit 250.23.

I agree with commentary, my opinion is based on the question asked. The question is if a tilt up wall can be used as a grounding electrode. If the tilt up wall is classified as a foundation wall I would agree that it could be used. I learned to make any interpretation based in the question asked.
 
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