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Grounding Rebar in footing

loucarabasi's picture

Just dug a footing and placed rebar as per specs, BI said I do not need to ground footing, because i am not puting in new service... ????!!!!

Is this true? if not, What is the proper way ground footing and what are the details

Thanks Fellas Lou C

As the twig bends- So grows the tree!!

By the way; This is an (post #194036, reply #1 of 13)

By the way; This is an addition to existing house

As the twig bends- So grows the tree!!

Your BI is right (post #194036, reply #7 of 13)

Ufers are in the current NEC for new construction services. In your case the service is not new, but a part of the existing house before your addition. Since you are not putting in a new service for the addition the ufer is not required. The older part of the house is grandfathered under the code in effect at the time it was built. All electrical work within the new addition however will need to pass whatever current addition of the NEC you jurisdiction is using, but since everything goes back to your original service that service meets the grandfather exemption.

Dave, So if I decide to (post #194036, reply #10 of 13)

Dave, So if I decide to ground footer, what is the proper way and route

Thanks Lou

BTW, I am in NJ

As the twig bends- So grows the tree!!

You don't ground the footer.  (post #194036, reply #11 of 13)

You don't ground the footer.  You may install a ground connection in the footer.  Entirely opposite concepts.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

NEC grounding. (post #194036, reply #12 of 13)

The NEC allows the rebar located in the bottom of the footing and encased in at least 2" of concrete to be used as the grounding electrode and/or 20' of bare #4 copper wire encased in the concrete footing.

It is covered under NEC 250.52 (A) (3).

Clamps and connectors must be listed and a bunch more stuff in that section that can confuse the heck out of a lot of people (electricians included).

Best thing to do is call the electrical inspector and ask how they want it done or hire and electrcian that has done several and knows what is acceptable to your AHJ. Most ufers need to be inspected before the footing is poured and the BI is not the guy to do the inspection unless he is also the elctrical inpsector (as he is in my county). If you try to do a ufer around here (adjoining counties) and the BI does not see a green sticker on it, they won't let you pour untill the electrical inspector passes it. then you have to reschedule the BI and the dance starts all over. A lot of hassel if your trying to keep on some kind of schedule.

Repost (post #194036, reply #13 of 13)

I've posted an answer twice, but apparently it keeps getting lost in cyber-space.

NEC article 250.52 (A) (3) covers concrete encased electrodes.

Spefically it says "consisting of bare or zinc galvanized or other electrically conductive coated steel, not less than 13mm (1/2") 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,"

If you use the rebar as the grounding electrode it must be connected to the ground wire (unbroken to the panel) with a listed connector. The whole thing must also be inspected before you pour your footing. Inspection must be by the EI and he will give you a green sticker (passed) or other documentation that the BI will need to see in order for him to pass you on the footing inspection.

At that point, IMO, you just created a scheduleing knot that can throw you off schedule with your other subs, for something you have already been told you don't need.

A Ufer isn't going to provide you with any more grounding protection than you already have.  Remember grounding paths are only going to carry direct faults to ground currents. Grounding conductors are not normally considered current carrying conductors and do not participents in a normal electric circuite operation. They are the "safety net" below the high wire act.

No amount of grounding is going save your electrical sytem from from a direct lightening hit on the SE cable or weatherhead. It may save your system if you recieve an indect hit on the structure itself, but you are still going to loose a bunch of electronics and such in the house. 

You've got it backwards.  A (post #194036, reply #2 of 13)

You've got it backwards.  A ground wire is placed in a footing to PROVIDE a ground.  Metal rods encased in concrete is known as a "Ufer" ground, and, since footings conveniently consist of concrete surrounding metal rods, footings are frequently used as the electrical system ground.

I don't know the detailed details, but to serve as a Ufer ground there must be a copper wire of the required size attached to the rebar in the footing in a special way.  The wire must be "protected" with conduit where it exits the concrete.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Grounding Rebar In Footing (post #194036, reply #3 of 13)

 

 

I sometimes wonder about the ideas that well-meaning
building engineers manage to put into building codes. Why use the footing rebar
for a ground? Have they ever seen what a direct strike can do to conductors?
When lightning hits it can blow a huge tree apart from the steam created from a
strike. When lightening hits a sand dune it will melt the sand to glass and
extend many feet in depth.

Now imagine dissipating a direct charge into the rebar of a
footing, I can see the rebar super-heated and the footing blown apart from a
direct hit. The heat would cause the moisture in the concrete to spall, there
goes the footing strength.

I wonder why not use a large piece of iron buried at footing
depth for the perceived grounding protection.

Sorry that I do not have your answer, but those were my thoughts on the subject.

Virginbuild



 

Upper Michigan

Instead of wondering (post #194036, reply #5 of 13)

You might want to google up Ufer ground and learn something new.

Joe H

Ufer ground (post #194036, reply #8 of 13)

Thanks for the tip. I did learn something, new to me. However, as per information I read for residential housing, a separate ground bar one half inch thick encased in concrete, at least two inches thick at footing level, and at least 20 feet long would be an alternative to using rebar in the footing. I would rather go that route then using rebar in the footing. IMHO.

Upper Michigan

What would be the difference, (post #194036, reply #9 of 13)

What would be the difference, other than your scheme would cost a bunch more?


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Ufers were designed for (post #194036, reply #6 of 13)

Ufers were designed for exactly that and they perform quite well in a lightning strike.

They are required in Florida as part of the footer inspection and we are the lightning capitol of the world

The NEC says they must be used when available. How far are you from the service? If it is close I would do it.

Greg

I installed foundation (post #194036, reply #4 of 13)

I installed foundation grounding in my new shop. (Washington state) The inspector told me to stub up a length of regular rebar through the bottom plate of the structure. This rebar was to be tied into the horizontal bars in the footing. The tying in was done with regular steel tie wire... nothing special. Simply tie it all together. If you want this ground to be accepted by the building official, it will have to be inspected prior to the placing of any concrete. My inspector put a signed sticker onto the stubbed up rebar. I tied into this with a copper ground clamp and copper wire and that was inspected prior to closing up the walls.