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  1. #1
    Jeff Pedigo's Avatar
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    Default UFER ground in a new slab?

    I have an situation with a residential dwelling that just had a new slab poured, but the foundation footings were not touched. The house already has two , correctly installed ground rods that have been properly bonded to gas and water lines, but no UFER was installed in the new slab. Should the UFER have been installed into the new slab or are the existing grounding rods sufficient?

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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jeff Pedigo View Post
    I have an situation with a residential dwelling that just had a new slab poured, but the foundation footings were not touched. The house already has two , correctly installed ground rods that have been properly bonded to gas and water lines, but no UFER was installed in the new slab. Should the UFER have been installed into the new slab or are the existing grounding rods sufficient?
    Does your soil require a UFER grounding system?

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    Default Re: UFER ground in a new slab?

    I'm not sure how UFER systems are installed in your area but the ones I have seen are in the foundation walls and footings, not in the slab. (I'm talking about houses with a basement, not a slab house.)

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    Default Re: UFER ground in a new slab?

    Its not a requirement unless stated in your plans... Your grounding rods should be all you need if installed correctly...

    As Bruce stated I have seen are in the foundation walls and footings, not in the slab...

    Best

    Ron


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    Default Re: UFER ground in a new slab?

    IF there is steel in that concrete, and there had better be in most cases, then the answer is "Yes, the grounding electrode system is required to be bonded to the concrete encased electrode."

    If the concrete encased electrode is "present" it is required to be bonded to the grounding electrode system.

    From the 2008 NEC. (underlining and bold are mine)
    - 250.50 Grounding Electrode System.
    - - All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.
    - - - Exception: Concrete-encased electrodes of existing buildings or structures shall not be required to be part of the grounding electrode system where the steel reinforcing bars or rods are not accessible for use without disturbing the concrete.

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    Default Re: UFER ground in a new slab?

    Even if the footer does not have steel in it , (if) you are still required to use a concrete encased electrode. You would need to use 20 feet of # 4 bare copper

    Last edited by ken horak; 01-10-2010 at 06:26 AM. Reason: added missed word "IF"

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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by ken horak View Post
    Even if the footer does not have steel in it , you are still required to use a concrete encased electrode. You would need to use 20 feet of # 4 bare copper
    Ken,

    Would you expand on that?

    I must be having a mental lapse as I am blanking on what you are referring to.

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    Jim Port's Avatar
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    Default Re: UFER ground in a new slab?

    Perhaps KH meant that the 20' of #4 could be used in place of the rebar and still qualify as a UFER.

    I also do not believe that a UFER could be installed in a slab. 250.52(3) calls for the CEE to be located near the bottom of the foundation or footing and in direct earth contact. A slab is certainly not either of these and the OP said the footing were not touched. Every slab I have ever seen was also poured over a vapor barrier that would prevent the direct earth contact.

    With that said I would not see how it would be required to bond any of the steel in the slab to the existing ground system.


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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jim Port View Post
    Perhaps KH meant that the 20' of #4 could be used in place of the rebar and still qualify as a UFER.
    Possibly, and if so, that would be correct.

    However, I took what Ken said as meaning a concrete encased electrode was required.

    I also do not believe that a UFER could be installed in a slab. 250.52(3) calls for the CEE to be located near the bottom of the foundation or footing and in direct earth contact. A slab is certainly not either of these and the OP said the footing were not touched. Every slab I have ever seen was also poured over a vapor barrier that would prevent the direct earth contact.

    With that said I would not see how it would be required to bond any of the steel in the slab to the existing ground system.
    A point which has been argued for some time, and which I was on that side of the argument for a long time.

    However ... the moisture barrier is required *under* the concrete ... which leaves the minimum 12 inch deep sides of the required minimum 12 inch deep concrete exposed to direct contract with earth, making the footing portion/foundation portion of the slab on grade (or slab on earth, or slab on ground, as some refer to it) the concrete encased electrode if there is steel reinforcing in it as there should be.

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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jerry Peck View Post
    However ... the moisture barrier is required *under* the concrete ... which leaves the minimum 12 inch deep sides of the required minimum 12 inch deep concrete exposed to direct contract with earth, making the footing portion/foundation portion of the slab on grade (or slab on earth, or slab on ground, as some refer to it) the concrete encased electrode if there is steel reinforcing in it as there should be.
    I might have gotten lost in all the double speak but is it possible that you are describing a monolithic pour?


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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jerry Peck View Post
    However ... the moisture barrier is required *under* the concrete ... which leaves the minimum 12 inch deep sides of the required minimum 12 inch deep concrete exposed to direct contract with earth, making the footing portion/foundation portion of the slab on grade (or slab on earth, or slab on ground, as some refer to it) the concrete encased electrode if there is steel reinforcing in it as there should be.
    Quote Originally Posted by Jim Port View Post
    I might have gotten lost in all the double speak but is it possible that you are describing a monolithic pour?

    Huh?

    If "slab on grade (or slab on earth, or slab on ground, as some refer to it)" is "double speak" then you must surely have a reading comprehension problem.

    That was three terms for the same construction method, stating the most common terms used for that construction method.

    Talk about meaning less speak "monolithic pour" describes "a method" of doing something, not what something is.

    Am I to presume that you do not know what the following are:
    - slab on grade
    - slab on earth
    - slab on ground
    ????

    Slab on ground is from the IRC.

    Slab on grade is what I've heard it called, and what I've called it, in most places around Florida as "grade" is "earth" or "ground" - pick your preferred term.

    Slab on earth is a term I've heard a few times describing slab on grade/slab on ground.

    Trying to say it in as simple of a way as possible for you as it appears you need for me to speak in simple terms.

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    Default Re: UFER ground in a new slab?

    I meant to ask if you were talking about a monolithic footing and slab. I also underlined the "doublespeak" I was referring to. It also seemed like you were saying the slabs had to be 12" thick.


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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jim Port View Post
    I meant to ask if you were talking about a monolithic footing and slab.
    Yes, that is how a slab on ground usually done, but not always.

    [/quote]I also underlined the "doublespeak" I was referring to. It also seemed like you were saying the slabs had to be 12" thick.[/quote]

    Read that again and you will see it is not double speak, it is stating: 1) what is there; 2) what is required.

    I could just as easily have stated: minimum 18 inch deep sides of the required minimum 12 inch deep concrete ... except that could cause confusion to someone not realizing that one is the depth as built and one is the minimum depth required, like you did not realize that. I used 12 inches for both as, at a minimum, both will be 12 inches. If I had stated 18 inches for the depth, I would have gotten responses from some saying that only 12 inches is done in their area, asking is that is okay, and the answer would be yes if there is no frost depth and only the minimum depth is required.

    But if you did not understand the first information, I doubt you understood what I just posted either.

    It also seemed like you were saying the slabs had to be 12" thick.
    Not "the slab" but "the footing" portion, yes, "the footing" portion needs to be 12 inches minimum into the ground - not 12 inches thick, but 12 inches into the ground, and another 8 inches (usually) above ground for much more than 12 inches thick.

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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jerry Peck View Post
    Ken,

    Would you expand on that?

    I must be having a mental lapse as I am blanking on what you are referring to.
    I missed a tiny word in my post - IF.
    There are jurisdictions that require a Concrete encased electrode .If this is the case and there is no steel , one would need to use 20 feet of # 4 bare copper


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    Default Re: UFER ground in a new slab?

    Just becuase there is re-bar in a concrete foundation/slab does not mean that the rebar is a electrode. Only in a pool or site-built spa is the repar required to be bonded to a GEC system, if the system has two electrode.

    This is currenty and has been the AHJ position around here for some time.


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    Default Re: UFER ground in a new slab?

    The origanal post said a slab was poured but the footing was not touched with this said unless the slab is in direct contact with the earth (no moisture barrier) no electrode exists. The footing may have the electrode but the code does not require it to be used if it is not accessible without disturbing the concrete.


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    Default Re: UFER ground in a new slab?

    As S. "Sparky" Freud once said: "Sometimes zee slab ist joost s slab." But, he might have continued, separated grounding electrodes are a good spark!

    Sometimes there's a seeming conflict between 'rules.' One example of this is the instructions on some CNC machining equipment, that tells you to drive a ground rod, but otherwise isolate it from the buildings' grounding system. The section of the NEC that Jerry cited was put there to make clear: tie all the grounds together.

    You would not, for example, want the grounding electrode for a service to be completely without connection to the ground you make on the secondaries of your transformers, generators, etc. To do so would create the possibility of the two 'grounds' being at different potentials, of the dirt itself acting as a conductor, etc.

    If a slab is not connected as a 'grounding electrode' anywhere, it's not a grounding electrode. It's just a slab - no matter the thickness, or how much steel is in it.

    As for the silliness about the plastic 'tub' under many buildings, they're irrellevant. Using the 'model' of 'the ground/neutral bond is for clearing faults, and the grounding electrode is for lightning,' I doubt that a plastic film exists that can withstand the millions of volts supplied by mother nature.


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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Stacey Van Houtan View Post
    Just because there is re-bar in a concrete foundation/slab does not mean that the rebar is a electrode. Only in a pool or site-built spa is the repar required to be bonded to a GEC system, if the system has two electrode.
    Quote Originally Posted by paul hardy View Post
    The origanal post said a slab was poured but the footing was not touched with this said unless the slab is in direct contact with the earth (no moisture barrier) no electrode exists. The footing may have the electrode but the code does not require it to be used if it is not accessible without disturbing the concrete.
    Both of the above are quite incorrect.

    IF there is steel in that slab which meets the minimum requirements for a concrete encased electrode then IT IS a concrete encased electrode.

    (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 ( in.) in diameter, ...

    If the steel rebar is at least 1/2" (#4 rebar) and is at least 20 feet long, then IT IS a concrete encased electrode. When is the last time anyone has seen less than #4 rebar used in a footing? And when is the last time someone as seen a footing less than 20 feet long? (That would be one VERY SMALL structure, say 4 feet by 4 feet or 6 feet by 3 feet.)

    Being as IT IS a concrete encased electrode, IT IS required to be bonded to the electrode grounding system - and it does not matter whether or not the builder provided a connection to that steel ... they need to chip the concrete out and provide for that connection ... and if they do that once or twice they will make sure they do not have to chip a third one out just to tie to the steel in that concrete encased electrode.

    There is but ONE exception, and that is IF the structure IS EXISTING ... not whether or not the footing is existing, but whether the structure is existing. If the builder screwed up and did not provide access to the concrete encased electrode, then like all their other screw ups they need to take corrective action. That is the only way some builders learn.

    The code requires ALL electrodes which are PRESENT to be bonded together, and there is #4 or larger steel in that footing, and it is encased in concrete, therefore, a concrete encased electrode IS PRESENT, and therefore IS REQUIRED to be bonded to all other electrodes ... regardless of how many other electrodes there are.

    The AHJ may not be enforcing that requirement, but IT IS A REQUIREMENT in the code nonetheless.

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    Default Re: UFER ground in a new slab?

    A question; was a new service installed?

    If not, no problem.

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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Darren Miller View Post
    A question; was a new service installed?

    If not, no problem.
    Let's do it this way:

    Quote Originally Posted by Jeff Pedigo View Post
    I have an situation with a residential dwelling that just had a new slab poured, but the foundation footings were not touched.

    AS LONG AS the new slab does not have any steel in it which is #4 or larger (which is why I kept stating footing because a footing would have #4 or larger) then the slab does not become a concrete encased electrode.

    *I PRESUMED INCORRECTLY* in my first post when I posted: "IF there is steel in that concrete, and there had better be in most cases, then the answer is "Yes, the grounding electrode system is required to be bonded to the concrete encased electrode." " as the slab would NOT have the required steel but a footing would, and I presumed that a NEW footing was also poured ... however, that was not what was said and was my error ... so if it is only a "slab" then it is unlikely to have the required steel in it to become a concrete encased electrode.

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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jerry Peck View Post
    Both of the above are quite incorrect.

    IF there is steel in that slab which meets the minimum requirements for a concrete encased electrode then IT IS a concrete encased electrode.

    (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 ( in.) in diameter, ...

    If the steel rebar is at least 1/2" (#4 rebar) and is at least 20 feet long, then IT IS a concrete encased electrode. When is the last time anyone has seen less than #4 rebar used in a footing? And when is the last time someone as seen a footing less than 20 feet long? (That would be one VERY SMALL structure, say 4 feet by 4 feet or 6 feet by 3 feet.)

    Being as IT IS a concrete encased electrode, IT IS required to be bonded to the electrode grounding system - and it does not matter whether or not the builder provided a connection to that steel ... they need to chip the concrete out and provide for that connection ... and if they do that once or twice they will make sure they do not have to chip a third one out just to tie to the steel in that concrete encased electrode.

    There is but ONE exception, and that is IF the structure IS EXISTING ... not whether or not the footing is existing, but whether the structure is existing. If the builder screwed up and did not provide access to the concrete encased electrode, then like all their other screw ups they need to take corrective action. That is the only way some builders learn.

    The code requires ALL electrodes which are PRESENT to be bonded together, and there is #4 or larger steel in that footing, and it is encased in concrete, therefore, a concrete encased electrode IS PRESENT, and therefore IS REQUIRED to be bonded to all other electrodes ... regardless of how many other electrodes there are.

    The AHJ may not be enforcing that requirement, but IT IS A REQUIREMENT in the code nonetheless.
    I will have to diagree with you saying that rebar in a slab meets the definition of a CEE. See the blue in (3) above. A slab on grade is not a foundation or footing, therefore it is not a CEE and would not require being bonded to the other grounding electrodes. Say you had 19'-11" of steel in the concrete footing, it does not meet the requirement and would not qualify either.


  22. #22
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    Default Re: UFER ground in a new slab?

    Jerry you are very correct in the current requirment bonding of Re-bar. This changed in 2005 from If a uffer was avaiable use to if it exist use it.

    Form a contractor view, personally it is so cheap that I would do it, reguardless of what the AHJ requirs. But from a HI perspective, I currently do not report the condition in detail since no AHJ in my area requires it and, in my opinion my libility in not increased due to my omission of more detail. I do have a standared comment on grounding and bonding i use:
    FYI- Although not always seen in residential dwellings, current electrical standards often recommend installing a "jumper wire" (usually a simple piece of wire) between the incoming and outgoing water heater pipes at   gas lines, dielectric fittings and other required areas to provide a continuity of the electrical bonding system. This feature is easy and inexpensive to install and was not currently present. The new owner may want to consider having this done.
    This is my current decesion of what report about this detail. This risk aynlsis is a continuing job and my opinion changes with time and expereience and knowledge.


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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jim Port View Post
    A slab on grade is not a foundation or footing, therefore it is not a CEE and would not require being bonded to the other grounding electrodes.
    A slab on ground IS a (*has a* is better wording, but I am going with your wording) a footing (actually *has* a footing).

    The monolithically poured (placed) concrete slab on ground has a footing around its perimeter, frequently referred to as "thickened edge" but which is really more than just a "thickened edge" - the perimeter is REQUIRED to have a footing as the footing is required to meet the minimum required footing sizes for the wall and load to be placed above it.

    - R403.1 General. All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, wood foundations, or other approved structural systems which shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill.

    The footing part of the concrete slab on ground must meet the requirements for minimum footing sizes.

    - R403.1.1 Minimum size. Minimum sizes for concrete and masonry footings shall be as set forth in Table R403.1 and Figure R403.1(1). The footing width, W, shall be based on the load-bearing value of the soil in accordance with Table R401.4.1. Spread footings shall be at least 6 inches (152 mm) thick. Footing projections, P, shall be at least 2 inches
    (51 mm) and shall not exceed the thickness of the footing. The size of footings supporting piers and columns shall be based on the tributary load and allowable soil pressure in accordance with Table R401.4.1. Footings for wood foundations shall be in accordance with the details set forth in Section R403.2, and Figures R403.1(2) and R403.1(3).

    The slab on ground has the footing in its thickened edge, the footing size must meet the required size, then the footing goes up at a 45 degree angle to meet the floor thickness, which is a minimum 3-1/2 inches.

    Say you had 19'-11" of steel in the concrete footing, it does not meet the requirement and would not qualify either.
    That is true, as I also said, and I pointed that if there is not more than 20 feet of steel in a footing - the structure would be VERY SMALL.

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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Stacey Van Houtan View Post
    This changed in 2005 from If a uffer was avaiable use to if it exist use it.

    Correct.

    In the 2002 NEC, the wording was "if available on the premises", in the 2005 NEC the wording changed to "that are present" and then added an exception for existing buildings to not require chipping the concrete out *on existing* buildings only.

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    Default Re: UFER ground in a new slab?

    On this foundation interpatation I would agree with you jerrry. Crawspace, basement, Raft, slab on grade All all foundations.

    If one wanted t carry this to a strict interpertation, on a post and pier foundaiton many times a bond would be required between peirs.

    Additionally the steel I-beam sitting on the foundation wall should be bonded.

    The steel in a Patio Slab or Drive and the foundation when the slabs touch?

    I have yet to see a fully bonded home.


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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Stacey Van Houtan View Post
    The steel in a Patio Slab or Drive and the foundation when the slabs touch?
    Nope. The steel is not #4 or larger. At least very few drives would have #4 rebar in them ... but if they did ...

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    Default Re: UFER ground in a new slab?

    Some times around here some will use #3 or (if left over #4) at the edge and 10x10 mesh in the field.

    Many times the patio rebar is doweled into the basement wall this would but the two rebars very close..

    When I was involved in pools many years ago All Rebar had to be connected (bonded)in all slabs, sidwalks and patio that were connected or touched and where the equipment wasmounted . This included slabs reguardless if rebar or mesh was used.

    But this was pools

    Of course around here any bonding would be a suprise except at pools


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    Default Re: UFER ground in a new slab?

    If there is an addition installed on a house and the electric service is not touched, then the new footing rebar is NOT required to be bonded.

    See the attached.

    Attached Files Attached Files
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    Default Re: UFER ground in a new slab?

    Jerry, apparently the style of construction is very different down south or the definition of a footing is not the same. Here a footing is typically 2' wide and 12" thick. There is no connection to the slab. A block foundation is laid on top of the footing and the slab would be poured on grade with an expansion joint against the wall and slab.

    Stacey, re this quote "On this foundation interpatation I would agree with you jerrry. Crawspace, basement, Raft, slab on grade All all foundations.

    If one wanted t carry this to a strict interpertation, on a post and pier foundaiton many times a bond would be required between peirs."

    Why would you say this? One ufer is enough and I am imagining a pier footing as 2-3' square and a foot thick or so. There would not be enough steel in this to qualify as another CEE.


  30. #30
    Stacey Van Houtan's Avatar
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    Default Re: UFER ground in a new slab?

    Many piers would have enough steel due to the tie connection, If the total length add up to 20' of all #4s than the = a 20' stick.

    I pose the question of bonding becuase, becuase I am not sure if the code intent is to bond all steel (as in pool or spa construction) or to provide the best Grounding electrode.
    See attached file on stray current

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  31. #31
    bob smit's Avatar
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    Default Re: UFER ground in a new slab?

    Some related notes;
    250.52 (a)(3) Where multiple CEE are present, only one need be connected to the GE sys. Was there an existing CEE in the footing?
    If not, one could be installed in the 'slab' if in fact no vapor barrier was used, (direct contact with earth).
    As stated prior, no CEE need be installed if service is not being changed and/or upgraded. However, not a bad idea if just (2) ground rods are being used.
    A 'slab' is not, by definition, a foundation or footing as far as AHJ's are concerned. Having said such, I would require a CEE if only no other was available and of course, in direct contact w/earth, but don't know where this would be done without a vapor barrier.
    Jerry was correct in mentioning "existing buildings or structures" as written in the code. However, one must use some common sense in these requirements when a part existing/part new situation is presented.

    I again have to cringe when I read that the electrodes required for an Electrical System are for lightning protection...ug!
    I'm not going to list the purpose for the GE System for an Electrical System yet again. Please search past posts in this regard.
    Bob Smit, County Electrical Inspector


  32. #32
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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jim Port View Post
    Jerry, apparently the style of construction is very different down south or the definition of a footing is not the same. Here a footing is typically 2' wide and 12" thick. There is no connection to the slab. A block foundation is laid on top of the footing and the slab would be poured on grade with an expansion joint against the wall and slab.
    Jim,

    Which is why the term "monolithic" and "monolithic slab" came up in the posts above.

    You are describing a separate footing which likely has a stem wall constructed on top of it which then has the slab poured on compacted fill, either floating (isolated from) the stem wall or keyed into the stem wall in some manner.

    That is a completely different type of construction than a slab on ground / slab on grade.

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  33. #33
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    Default Re: UFER ground in a new slab?

    Jerry, this is your quote from post #5.
    Quote Originally Posted by Jerry Peck View Post
    IF there is steel in that concrete, and there had better be in most cases, then the answer is "Yes, the grounding electrode system is required to be bonded to the concrete encased electrode."

    If the concrete encased electrode is "present" it is required to be bonded to the grounding electrode system.

    From the 2008 NEC. (underlining and bold are mine)
    - 250.50 Grounding Electrode System.
    - - All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.
    - - - Exception: Concrete-encased electrodes of existing buildings or structures shall not be required to be part of the grounding electrode system where the steel reinforcing bars or rods are not accessible for use without disturbing the concrete.
    The OP said that the slab was new and the footers had not been touched. This would rule out the possibility that a monolitic footing and slab was used. This would mean that the steel would not satisfy the location requirement for being in the footing. Therefore your answer above in blue is incorrect regarding the specific situation mentioned.

    Your answer could be correct if the situation were a different type of installation.

    I believe that you are a stickler for proper terminology and reading what was posted. Again in post #18 you again gave incorrect information regarding the situation in regards to the OPs original question and reinforced by this quote.
    Quote Originally Posted by paul hardy View Post
    The original post said a slab was poured but the footing was not touched with this said unless the slab is in direct contact with the earth (no moisture barrier) no electrode exists. The footing may have the electrode but the code does not require it to be used if it is not accessible without disturbing the concrete.
    Quote Originally Posted by Jerry Peck View Post
    Both of the above are quite incorrect.

    IF there is steel in that slab which meets the minimum requirements for a concrete encased electrode then IT IS a concrete encased electrode.

    (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 ( in.) in diameter, ...

    If the steel rebar is at least 1/2" (#4 rebar) and is at least 20 feet long, then IT IS a concrete encased electrode. When is the last time anyone has seen less than #4 rebar used in a footing? And when is the last time someone as seen a footing less than 20 feet long? (That would be one VERY SMALL structure, say 4 feet by 4 feet or 6 feet by 3 feet.)

    Being as IT IS a concrete encased electrode, IT IS required to be bonded to the electrode grounding system - and it does not matter whether or not the builder provided a connection to that steel ... they need to chip the concrete out and provide for that connection ... and if they do that.....
    Think you missed the mark.


  34. #34
    ken horak's Avatar
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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by bob smit View Post
    Some related notes;

    I again have to cringe when I read that the electrodes required for an Electrical System are for lightning protection...ug!
    Bob Smit, County Electrical Inspector
    Well we all know that it is not for the purpose of clearing faults.
    And we all know that electricity is always seeking it way back to it's source ( not earth as previouly believed by many)

    Topic for another day


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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jim Port View Post
    Think you missed the mark.
    Jim,

    That I did.

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  36. #36
    Jim Port's Avatar
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    Default Re: UFER ground in a new slab?

    Quote Originally Posted by Jerry Peck View Post
    Jim,

    That I did.
    Thank you for that gracious admission.


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    Default Re: UFER ground in a new slab?

    Thank you all for your participation ...

    Bob Smit, I think you'll find my comments about the grounding electrode being there 'for lightning' to be a rather orthodox view. Perhaps you might do a search of some electrical sites, like Mike Holt's, for more discussion on this point that even I can stomach.

    Suffice it to point out that there are several quite modern countries that get along just fine without any grounding electrodes at all. Neither the house nor the power company need them in order to function properly. All the other, esoteric reasons advanced for grounding electrodes ('reference plane,' etc.) stumble over this simple fact.

    You can even show where the use of the grounding electrode for any purpose besides lightning is the direct cause of transient voltage, or voltage gradient, issues.

    I'll repeat again that simple math proves that the grounding electrode has no role in clearing faults. Please note that the NEC allows the grounding electrode to have as much as 25 ohms of resistance. Ohms law tells us that such an electrode would carry less than 5 amps of current- nowhere near enough to trip any breaker or blow any fuse.

    Another indication of just how small a role the grounding electrode plays in the electrical system is that the wire to it (the GEC) maxes out at #6, regardless of service size. It seems pretty clear that no one expects that wire to carry even 200 amps.

    Perhaps you are trying to say that there is a role for lightning rods, etc., in lightning protection. I will not deny that.

    Which, of course, boxes us in rather nicely: if we don't need them for any other reason, and they're inadequate for lightning, what good are they at all?

    This is not as silly a question as it may appear. Article 250 has only recently bugun to be cleaned of some of the contradictions, nonsense, and confusion it holds - all the result of decades of using different theories as to what grounding and bonding were meant to accomplish.


  38. #38
    Stacey Van Houtan's Avatar
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    Default Re: UFER ground in a new slab?

    I did a HI for a insurance re-insurer in KS, Per Him: A major cause of fires in the flat TOTO land, a some call it, was lighting strikes, His actural sources said the if a effective GE was present it greatly redueced a lighting strike causing a fire.


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