# Ufer Ground?



## normel (Oct 3, 2007)

If a new footer for a retaining wall is only 12' long but will contain more than 20' of rebar along the bottom of the trench (two parallel pieces that could be tied together), does the rebar meet the qualifications of a concrete encased electrode? 

The wall is adjacent to where the new (updated) service will be installed.


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## Bob Badger (Apr 19, 2009)

As long as you have at least 20' of 1/2" or larger rebar that is tied together near the bottom of a footing that is in direct contact with the earth you have a uffer.


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## frenchelectrican (Mar 15, 2007)

Sorry to bother ya guys but can you expand little more on the details with UFER rods I know you say to tie together to get total of 20 feet {6m} but which way you will have approved way to tie it properly?

Merci,Marc


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## Bob Badger (Apr 19, 2009)

Hi Marc, Strangely as it seem the NEC allows the sections to be tied together with just the normal bailing wire used to secure re-bar. But the connection between the re-bar and the copper conductor will have to be approved for the use.


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## sparkyboys (May 3, 2009)

i would go ahead and cad weld the ufer to the rebar as a just in case for the new service. also check your specs to see what it says.


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## Bob Badger (Apr 19, 2009)

sparkyboys said:


> i would go ahead and cad weld the ufer to the rebar


Unless your into wasting copper the re-bar is the ufer.


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## sparkyboys (May 3, 2009)

Bob Badger said:


> Unless your into wasting copper the re-bar is the ufer.


i like wasting copper


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## Bob Badger (Apr 19, 2009)

sparkyboys said:


> i like wasting copper


As long as you understand your not making anything better.

There is a reason the NEC only requires 4 AWG to a ufer no matter what the service size is.


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## nrp3 (Jan 24, 2009)

Why is that? I've got to do one soon on a 400a service and the last one I did, I put a 1/0 on it not realizing that all you needed was #4. Looking it up I agree, but whats the reasoning behind the small size?


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## Dennis Alwon (May 9, 2009)

nrp3 said:


> Why is that? I've got to do one soon on a 400a service and the last one I did, I put a 1/0 on it not realizing that all you needed was #4. Looking it up I agree, but whats the reasoning behind the small size?


The only thing I can think of is that the ufer itself is only as good as a #4 conductor so why put in larger. The same is true of a ground rod-- #6 max. no matter what the service size.


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## william1978 (Sep 21, 2008)

sparkyboys said:


> i like wasting copper


 Set all that copper aside that you like wasting and when you get a big pile PM me and I'll come and get it and take it to a scrap yard and I'll even give you a cut.:thumbup:


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## Bob Badger (Apr 19, 2009)

Dennis Alwon said:


> The only thing I can think of is that the ufer itself is only as good as a #4 conductor so why put in larger. The same is true of a ground rod-- #6 max. no matter what the service size.


That is how I understand it, the connection of the ufer to the dirt will limit the total amount of current that can be carried on the GEC.


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## frenchelectrican (Mar 15, 2007)

Bob Badger said:


> Hi Marc, Strangely as it seem the NEC allows the sections to be tied together with just the normal bailing wire used to secure re-bar. But the connection between the re-bar and the copper conductor will have to be approved for the use.


 
Bob., 

Belive or not it the same thing in France as well I thought it will be diffrent but I guess not.,,, oh well. Thanks for expaining to me.

Merci,Marc


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## sparkyboys (May 3, 2009)

Bob Badger said:


> As long as you understand your not making anything better.
> 
> There is a reason the NEC only requires 4 AWG to a ufer no matter what the service size is.


i understand that the ufer is the rebar, but you still have to attach the #4 to it, if the new wall rebar is not attached to the existing rebar of the existing building. that wall still has to be grounded


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## manchestersparky (Mar 25, 2007)

Keep in mine the rebar must be in the bottom 2" of the concrete.
There can not be any plastic sheeting under the footer either.


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## Dennis Alwon (May 9, 2009)

manchestersparky said:


> There can not be any plastic sheeting under the footer either.


And where is this written?


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## 480sparky (Sep 20, 2007)

dennis alwon said:


> and where is this written?


250.52(a)(3).


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## william1978 (Sep 21, 2008)

I think Dennis is talking about the poly.


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## Dennis Alwon (May 9, 2009)

480sparky said:


> 250.52(a)(3).



IMO that does not eliminate plastic on the bottom of the footer. The footer can still be in direct contact with the earth and have plastic under it.


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## manchestersparky (Mar 25, 2007)

"in direct contact with the earth"
Article 250.52 (A) (3)

If the footer has poly under it it is not in direct contact with the earth -
it is in a sense insulated from the earth


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## william1978 (Sep 21, 2008)

manchestersparky said:


> "in direct contact with the earth"
> Article 250.52 (A) (3)
> 
> If the footer has poly under it it is not in direct contact with the earth -
> it is in a sense insulated from the earth


 I agree. :thumbsup:


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## Dennis Alwon (May 9, 2009)

manchestersparky said:


> "in direct contact with the earth"
> Article 250.52 (A) (3)
> 
> If the footer has poly under it it is not in direct contact with the earth -
> it is in a sense insulated from the earth



I disagree... The sides of the footer are still in direct contact with the earth.


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## MDShunk (Jan 7, 2007)

Call me crazy, but footer is generally underground. If it was sitting on poly, wouldn't the sides necessarily be in contact with the earth, making the ufer in contact with the earth? Or, are you thinking that the bottom 2" of the footer is the ufer, so the majority of the ufer is insulated, regardless how tall the footer is?


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## william1978 (Sep 21, 2008)

Dennis Alwon said:


> I disagree... The sides of the footer are still in direct contact with the earth.


 Why does the rebar need to be near the bottom then?


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## nick (Feb 14, 2008)

manchestersparky said:


> "in direct contact with the earth"
> Article 250.52 (A) (3)
> 
> If the footer has poly under it it is not in direct contact with the earth -
> it is in a sense insulated from the earth


Well generally most footers dont have poly under them just the slab part your bug screen and moisture barrier . 
Column pads & footers are exposed to earth on most of the work we do . Take care


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## william1978 (Sep 21, 2008)

I'm glad we don't have to worry about this in NC.


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## Dennis Alwon (May 9, 2009)

william1978 said:


> Why does the rebar need to be near the bottom then?



I believe the ufer is near the bottom so as to get as much moisture as possible however, there is no wording that says the poly cannot be under the footer. Moisture will still penetrate the sides near the bottom.

Now I do believe it would be better to not have the poly but I don't see where the code denies us doing this.


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## Dennis Alwon (May 9, 2009)

william1978 said:


> I'm glad we don't have to worry about this in NC.


On new construction in NC I always use a ufer ground. Why not it is 10 times better than 2 rods.


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## william1978 (Sep 21, 2008)

Dennis Alwon said:


> On new construction in NC I always use a ufer ground. Why not it is 10 times better than 2 rods.


 I agree. What I meant was the Inspector can't make you install it if you didn't want to.


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## Dennis Alwon (May 9, 2009)

william1978 said:


> I agree. What I meant was the Inspector can't make you install it if you didn't want to.


This is true but I wish NC would change their tune on that call.


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## william1978 (Sep 21, 2008)

Dennis Alwon said:


> This is true but I wish NC would change their tune on that call.


 I agree. Its the damn BDC.


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## normel (Oct 3, 2007)

Somewhere amidst all the talk about wasted copper and poly-lined footers I think there was an answer to my question... as long as there is 20' of 1/2" rebar, even if it is looped back on itself in a 12' trench, it meets the requirements of a Ufer...correct?


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## william1978 (Sep 21, 2008)

Yes.........


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## leland (Dec 28, 2007)

250.52(A)(3)

foundation OR footing. reading footing here a lot. 
Just make sure it is in the concrete and that concrete is surrounded by earth.

Still the tie with bailing wire...go figure... oh well.


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## frenchelectrican (Mar 15, 2007)

normel said:


> Somewhere amidst all the talk about wasted copper and poly-lined footers I think there was an answer to my question... as long as there is 20' of 1/2" rebar, even if it is looped back on itself in a 12' trench, it meets the requirements of a Ufer...correct?


 
Yes it do meet the requirement as I did asked to expand the related question and Bob Badger is kind engough to answer to the point and he is right.

Merci,Marc


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## erics37 (May 7, 2009)

normel said:


> Somewhere amidst all the talk about wasted copper and poly-lined footers I think there was an answer to my question... as long as there is 20' of 1/2" rebar, even if it is looped back on itself in a 12' trench, it meets the requirements of a Ufer...correct?


That inspires me to ask... if a standard stick of 1/2" rebar is 20' feet long, and it has a 90 bent in it so it sticks above the concrete a few feet for your GEC & clamp, is that adequate? Or does there need to be 20' of rebar inside the actual concrete, even if you have to tie another stick on?


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## rexowner (Apr 12, 2008)

erics37 said:


> That inspires me to ask... if a standard stick of 1/2" rebar is 20' feet long, and it has a 90 bent in it so it sticks above the concrete a few feet for your GEC & clamp, is that adequate? Or does there need to be 20' of rebar inside the actual concrete, even if you have to tie another stick on?


Nope. The electrode is only that portion encased by
concrete, and is required to be 20'.


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## RePhase277 (Feb 5, 2008)

When I first began installing ufers, I worked for a company and did pretty much what I was told. Then I began to actually read the Code. At that time, the ufer was only installed if the plans called for it, but there was no enforcement. We did bazillions of pool houses for a builder, and the plans always called for a ufer, but no specs otherwise. The boss, in his infinite wisdom ordered the wire based on T250.66.

When I began reading the code, I discovered that it didn't need to be larger than #4. When I told the boss, he said "No. You see, you have to look at the table, and... um... it's right here........ son of a bitch". He had bought untold thousands of $$ worth of bare 1/0, and just realized he only need #4:laughing:


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## I Conduit (May 4, 2009)

Dennis Alwon said:


> IMO that does not eliminate plastic on the bottom of the footer. The footer can still be in direct contact with the earth and have plastic under it.


Inspectors in my area will not pass poly under a footing. I also attended a grounding and bonding seminar and the instructor said the same.


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## Rockyd (Apr 22, 2007)

> Inspectors in my area will not pass poly under a footing. I also attended a grounding and bonding seminar and the instructor said the same.


Exactly. The way Dennis is wanting to do it, would equal a capacitor of sorts. The whole point is to discharge higher voltages per 250.4(A)(1) and (2).


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## Dennis Alwon (May 9, 2009)

Rockyd said:


> Exactly. The way Dennis is wanting to do it, would equal a capacitor of sorts. The whole point is to discharge higher voltages per 250.4(A)(1) and (2).


Hold on there Rocky... I didn't say I wanted to do it that way just that there is no wording in the code that states I cannot do it. If the footer were wrapped in plastic that would be another story but just on the bottom-- I am not sure I understand how that would be a capacitor of sorts..


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## Dennis Alwon (May 9, 2009)

I Conduit said:


> Inspectors in my area will not pass poly under a footing. I also attended a grounding and bonding seminar and the instructor said the same.


That may be the case but I still don't see the wording that won't allow it.


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## Bob Badger (Apr 19, 2009)

Dennis Alwon said:


> there is no wording that says the poly cannot be under the footer.


Of course you can have poly under the footing but then you will not have a ufer.

If there is plastic under the footing the concrete is not in direct contact with the earth.


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## william1978 (Sep 21, 2008)

Bob Badger said:


> Of course you can have poly under the footing but then you will not have a ufer.
> 
> If there is plastic under the footing the concrete is not in direct contact with the earth.


 I second that.


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## 480sparky (Sep 20, 2007)

There's a difference between what is under a footing and what is next to it.

_Under_ a footing should be _undisturbed earth_. Who knows what gets put in _next_ to it. Maybe pea gravel and/or corrogated pipe for drainage. Maybe sand. Maybe all crap the excavator wants to make disappear. Maybe Jimmy Hoffa.......


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## Dennis Alwon (May 9, 2009)

Bob Badger said:


> Of course you can have poly under the footing but then you will not have a ufer.
> 
> If there is plastic under the footing the concrete is not in direct contact with the earth.



How is the footer not in contact with the earth? The plastic is on the bottom and the sides are below grade-- thus in contact with the earth.


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## 480sparky (Sep 20, 2007)

Dennis Alwon said:


> How is the footer not in contact with the earth? The plastic is on the bottom and the sides are below grade-- thus in contact with the earth.


See my post right before yours.:whistling2:


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## Bob Badger (Apr 19, 2009)

Dennis Alwon said:


> How is the footer not in contact with the earth? The plastic is on the bottom and the sides are below grade-- thus in contact with the earth.


If it is still in direct contact with the earth even with plastic under it can you give me a real world example of a footing that is not in direct contact with the earth?


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## Dennis Alwon (May 9, 2009)

Bob Badger said:


> If it is still in direct contact with the earth even with plastic under it can you give me a real world example of a footing that is not in direct contact with the earth?



I have heard of people wrapping the entire footer with plastic. I would think this is not in contact with the earth. I understand this is your opinion and one I basically agree with. I think the code needs some rework here because it is not cut and dry. I am not the only one that believes what I am saying.

You say the footer has plastic on the bottom then it is not in contact with the earth. I say it is--- you cannot tell me it isn't in contact with the earth because you would be wrong. Does it meet the intent of the code? I don't know. I believe you have used Charlie's rule before so......you know where I am coming from with this. You don't have to agree---


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## Dennis Alwon (May 9, 2009)

480sparky said:


> See my post right before yours.:whistling2:


I did read your post and it has nothing to do with the wording of the code. The word "under" isn't even used in 250.52(A)(3). :whistling2:


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## Bob Badger (Apr 19, 2009)

From the IAEI online magazine.



> Where a footing is separated from the earth by a plastic or other insulating (vapor) barrier, the concrete-encased electrode is not present (see photos 1 and 2). The Code defines grounding electrode as “a device that establishes an electrical connection to the earth.”












Photo 1. Vapor barriers create isolation between the concrete and the earth. These are not suitable for use as concrete-encased grounding electrodes. (Photo courtesy of Robert Jones, IEC)













Photo 2. Close up. Vapor barriers create isolation between the concrete and the earth. These are not suitable for use as concrete-encased electrodes.

http://www.iaei.org/magazine/?p=1855

The IAEI is not the NFPA but inspectors do listen to what the IAEI tells them and an inspector that had just read "Where a footing is separated from the earth by a plastic or other insulating (vapor) barrier, the concrete-encased electrode is not present " is going to remember that.


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## 480sparky (Sep 20, 2007)

Dennis Alwon said:


> I did read your post and it has nothing to do with the wording of the code. The word "under" isn't even used in 250.52(A)(3). :whistling2:


But it certainly is the point of contention in this discussion.


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## Dennis Alwon (May 9, 2009)

Bob your photos are not what is being discussed. The sides were not encased in plastic. It was about having plastic under the footer. 

I really do not feel the need to back my statements any longer. I have made my feelings clear and you can accept it or not. The words, IMO, do not prohibit this install. What more can I say.


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## Bob Badger (Apr 19, 2009)

Dennis Alwon said:


> Bob your photos are not what is being discussed. The sides were not encased in plastic.


There is a full 12" of the footer sides exposed.


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## Dennis Alwon (May 9, 2009)

Bob Badger said:


> There is a full 12" of the footer sides exposed.


Looks to me like it's a monolithic pour and the footer that is not in plastic is part of the slab and above grade. Regardless, the idea is for moisture to be at the bottom of the footer. I don't see much moisture getting there with that pour yet with the plastic on the bottom I can see much moisture getting there. 

Again, I don't have the answers-- I think this section needs clarification. When everyone interprets it differently there is a problem and like I said, I am not the only one who looks at it the way I do.


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## Bob Badger (Apr 19, 2009)

Dennis Alwon said:


> Again, I don't have the answers--


Mike Holt's answer



> *Q.* When a vapor barrier has been installed under a footer, can the steel rebar above the vapor barrier be used as a grounding electrode?
> 
> *A.* No. A concrete-encased electrode of the steel rebar type is only suitable to be used as a concrete-encased electrode if it's located within and near the bottom of a concrete foundation or footing in direct contact with the earth [250.52(A)(3)]. If a vapor barrier is installed between the footer and the earth, then the rebar can't be used as an electrode.


http://ecmweb.com/nec/electric_stumped_code_29/


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## Dennis Alwon (May 9, 2009)

And that is Mike's opinion, which he is entitled to. The words remain the same.


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## Bob Badger (Apr 19, 2009)

Dennis Alwon said:


> And that is Mike's opinion, which he is entitled to. The words remain the same.


Very true as you are entitled to yours, I don't always agree with Mike. 

But IMO the majority of inspectors are going to see it like Mike.


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## Dennis Alwon (May 9, 2009)

Bob Badger said:


> Very true as you are entitled to yours, I don't always agree with Mike.
> 
> But IMO the majority of inspectors are going to see it like Mike.


I agree and I am not arguing that at all.


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## leland (Dec 28, 2007)

Thanx for the photos Bob. Great illustration.:thumbsup:
That situation (a slab house) I would agree no chance of a UFER.

Here in New England we have basements,the footer can be anywhere from 4 to 10 ft below grade. So that vapor barrier can be around the footing and under the basement slab.Leaving the FOUNDATION wall exposed in direct contact with the earth. 
Nowhere does it state you need 4 sides in contact. 250.52(A)(3) states "footing OR foundation".
IMO this would be an acceptable UFER.

Except for that water proofing stuff they paint on the foundation walls,unless it is conductive.
That changes every thing.


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## I Conduit (May 4, 2009)

Dennis Alwon said:


> That may be the case but I still don't see the wording that won't allow it.


The wording is not there, I agree but the wording is also not there to stop you from putting rocks, sand, or other things in the bottom of the footer. The NEC cannot possibly list all of the scenarios that happen from job to job. I think the words "direct contact" tell me that there is to be nothing between the concrete and the earth for it to an acceptable method of grounding. Just MHO.


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## Dennis Alwon (May 9, 2009)

I Conduit said:


> The wording is not there, I agree but the wording is also not there to stop you from putting rocks, sand, or other things in the bottom of the footer. The NEC cannot possibly list all of the scenarios that happen from job to job. I think the words "direct contact" tell me that there is to be nothing between the concrete and the earth for it to an acceptable method of grounding. Just MHO.



Again, Is there not direct contact with the earth on the sides of the footer. Yes there is so the CMP needs to clarify what is acceptable and what isn't. I and many others seem to think that the plastic may not be a good idea but I am not sure that it would affect the ufer. I would love to do a 3 point test on one and see what it would end up being.


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## manchestersparky (Mar 25, 2007)

Wow - I never thought that one sentence would result in pages of debate.

OK here's what I was taught take it or leave it as it's up to interpretation 
250.52 (A) (3) -
An electrode encased by at least 50mm ( 2inches) of concrete,located horizontally near the bottom or vertically,and within that portion of a concrete foundation that is in direct contact with the earth,consisting of at least 20' ......blah blah blah ( we all know the rest or can look it up)

The uffer is to be encased by 2" of concrete and WITHIN that portion of the footer that is in direct contact. 
The Concrete encased electrode is within 2" of the bottom- it is "within" that portion thats in direct contact with earth. plastic under the footer eliminates the "within" that portion in direct contact.
Only run into the issue when theres a monolithic pour


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## uncle fester (May 30, 2009)

normel said:


> If a new footer for a retaining wall is only 12' long but will contain more than 20' of rebar along the bottom of the trench (two parallel pieces that could be tied together), does the rebar meet the qualifications of a concrete encased electrode?
> 
> The wall is adjacent to where the new (updated) service will be installed.


Hey ufer dude? Do you own a code book?


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## Dennis Alwon (May 9, 2009)

uncle fester said:


> Hey ufer dude? Do you own a code book?


That's pretty abrasive for a first post. It also doesn't help the situation at all.


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## vinster888 (May 3, 2009)

(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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## zen (Jun 15, 2009)

it will be obvious that i know little on this subject,,so ,,when we run a uffer ground we do it with 20 feet of #4 bare but from what im reading the rebare cane be used as the uffer?


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## Dennis Alwon (May 9, 2009)

zen said:


> it will be obvious that i know little on this subject,,so ,,when we run a uffer ground we do it with 20 feet of #4 bare but from what im reading the rebare cane be used as the uffer?



You tie your #4 to the rebar in the footing and then you don't need 20' of wire, just enough to tie to the rebar. The rebar must be 20 foot long and at least 1/2" thick. The rebar can be tied together with steel wire as long as the total length is 20' or longer.

Read art. 250.52(A)(3)


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## william1978 (Sep 21, 2008)

zen said:


> it will be obvious that i know little on this subject,,so ,,when we run a uffer ground we do it with 20 feet of #4 bare but from what im reading the rebare cane be used as the uffer?


 Just tie the #4 to the 20' piece of rebar.


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## manchestersparky (Mar 25, 2007)

william1978 said:


> Just tie the #4 to the 20' piece of rebar.


Using an approved method of course

clamp rated for the use or exothermic weld


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## vinster888 (May 3, 2009)

Dennis Alwon said:


> IMO that does not eliminate plastic on the bottom of the footer. The footer can still be in direct contact with the earth and have plastic under it.


no, you are sadly mistaken. what you do is plastic the main part of the slab just not the footer areas. plastic is a great insulator. therefore if the pastic covered the whole thing there would be minimal contact with the earth around the edges


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## william1978 (Sep 21, 2008)

manchestersparky said:


> Using an approved method of course
> 
> clamp rated for the use or exothermic weld


 Yes your correct. I just take that stuff for granted.:thumbsup:


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## zen (Jun 15, 2009)

mr. sparky can you help me out on the ufer post i am the last post


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## Dennis Alwon (May 9, 2009)

vinster888 said:


> no, you are sadly mistaken. what you do is plastic the main part of the slab just not the footer areas. plastic is a great insulator. therefore if the pastic covered the whole thing there would be minimal contact with the earth around the edges


Thank you for your opinion. I do not want to go here again.


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## william1978 (Sep 21, 2008)

Dennis Alwon said:


> Thank you for your opinion. I do not want to go here again.


 Me either.:no:


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## Benaround (May 5, 2009)

Look at it this way, after the first lightning strike there won't be any more

plastic vapor barrier to worry about !!


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## azca (Aug 2, 2009)

Folks, there are some poor answers here. 

First, 12 feet of footing will NOT be sufficient, even if you use 20' of condcutor. Yes you may meet the wording of the code but not the intent. Concrete is actually a good conductor of electricity (who knew) and when a conductor is encased in the concrete, the footing itself becomes the conductor. To be a concrete encased electrode you need 20 feet of footing length, not wire. This is why a #4 is all that is needed, increasing the conductor size will have little, if any, impact on the effectiveness of the conductor. Same reason you must drive ground rods a minimum of 6 feet apart, if installed closer, they loose their effectiveness. A good rule of thumb actually is to install the rods on rod length appart. For grounding, farther apart is better.

Two. Plasting under or around the footing is a serious problem for a Ufer. The goal of the footing as a conductor is to electrically tie the grounding system to the same potential as the earth. Plastic is an insulator, think of it this way, would you install a #4 ufer with the insulation still on it?

Three ufers work well as the concrete has the building putting pressure against the conductor and the earth providing for good contact. Adding to this concrete is a moisture sponge, it will absorb moisture from the surrounding soil increasing the effectiveness. 

For better understanding of what a concrete encased electrode is you can read up on it in a book published by the IAEI, it is called the SOARES book on grounding.


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