This article was posted 03/22/2006 and is most likely outdated.

The Use of Concrete-Enclosed Reinforcing Rods as Grounding Electrodes
 

 
Topic - Grounding and Bonding
Subject - The Use of Concrete-Enclosed Reinforcing Rods as Grounding Electrodes

March 22, 2006  

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The Use of Concrete-Enclosed Reinforcing Rods as Grounding Electrodes

 

The findings of Ufer that metal encased in concrete performs as an effective grounding electrode constitutes a major breakthrough in grounding technology. This has been recognized to the extent that copper wire embedded in the concrete footings of a structure is now an acceptable alternate to driven rods or pipe electrodes in the soil. This comes as a welcome relief from the condition of ineffective grounding by the use of water pipes due to insulated material or couplings and the antagonism of the proprietors of the water pipes.

 

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Comments

  • I have to wonder if the same effective earth ground can be obtained by encasing a #4 AWG conductor or a 20' piece of 1/2" rebar in the concrete slab of a basement. Why does the UFER ground need to be in the footing? What about burying a 20' piece of rebar 12" in the dirt, then pouring concrete over it? Would that not provide an effective ground?

    Tim

    • Reply from: George Stolz   
    " * I have to wonder if the same effective earth ground can be obtained by encasing a #4 AWG conductor or a 20' piece of 1/2" rebar in the concrete slab of a basement. Why does the UFER ground need to be in the footing?"

    I believe the intent is to connect to the existing rebar at the point at which there is the highest occurance of moisture in the surrounding soil. I believe the pressure of the structure resting on the footer would enhance the connection of the concrete-encased electrode to the earth.

    The more rebar that is tied together, the better and more redundant the connection to earth would be. Therefore, in my opinion, the use of the rebar would be a superior connection to earth as opposed to the 20 feet of #4 method.

    "What about burying a 20' piece of rebar 12" in the dirt, then pouring concrete over it?"

    That would not be a CCE according to 250.52(A)(3), as it is to be encased by 2" of concrete. If you pour over rebar laying on the ground, then it's not encased: the underside is not in contact with the concrete.

    "Would that not provide an effective ground?" Whether it did or not, it would not be considered a true grounding electrode by the NEC, in my opinion.

    In my opinion, the rebar is to connect the Grounding Electrode Conductor to the concrete, which in turn in porous, which in turn absorbs water, which all taken together makes a killer connection to the earth.

    Reply from: Mike Holt   
    George, you are 100% correct in all of our statements!

    Reply from: T.M.Haja sahib   
    George, encasing of bare conductor all around by concrete in ground is for corrosion protection and not for the purpose you state in the last para.

    Reply from: Laszlo Weress   
    T.M. ,

    Sorry, but George is correct.

    Concrete itself is corrosive. Test the ph and you will find it highly alkaline. Not to mention that when used as a case or a neutral ground the DC component of the circulating currents makes it a perfect electrode of a battery, thus corrosion is accelerated.

    Reply from: T.M.Haja sahib   
    Lazslo, Your assertion is false in case rebar is used as earth electrode because concrete provides a protective layer over the electrode preventing corrosion.Otherwise how could RCC structures exist for a long time with stability?

    Reply from: T.M.Haja sahib   
    Laszlo,I mean concrete enclosed rebar of same material as that of building.
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