Rebar as CEE - lap splice required?

[Darren Emery]

Hello all -

I have posted a few times in the past - but have been lurking here to learn more about the NEC for years. You all are a wealth of knowledge. Often my go-to when I need to study a topic in depth. Thank you!

I would really appreciate input regarding the CEE method in the picture below.

The IRC is our governing document for residential install, but it mirrors well the requirements from the NEC. By both codes, the rebar is allowed to be bonded together with wire tires, or other effective methods. I have always wondered if the intent of this language to allow for the appropriate lap splice of the rebar (approximately 24") to act as a bonding point, rather than the perpendicular intersection as shown.

My understanding of the CEE is that it relies on the extensive surface contact between either the wire or the bar (20' minimum) with the concrete to function correctly. If we consider the bottom bar in the trench shown as the actual CEE, the connection point at the intersection of the vertical painted bar to the horizontal bottom bar seems tome to be a weak point. . A 90deg bent bar, with at least 24" of bar to bar contact, and then wire tied, would offer a better path for current flow, IMO.

Thoughts on this?

(BTW - the bars will be lifted and fully encased in concrete when poured... not in conctact with the soil, just in case you were worried about that!)

 

[Gregg Harris]

Hello all -

I have posted a few times in the past - but have been lurking here to learn more about the NEC for years. You all are a wealth of knowledge. Often my go-to when I need to study a topic in depth. Thank you!

I would really appreciate input regarding the CEE method in the picture below.

The IRC is our governing document for residential install, but it mirrors well the requirements from the NEC. By both codes, the rebar is allowed to be bonded together with wire tires, or other effective methods. I have always wondered if the intent of this language to allow for the appropriate lap splice of the rebar (approximately 24") to act as a bonding point, rather than the perpendicular intersection as shown.

My understanding of the CEE is that it relies on the extensive surface contact between either the wire or the bar (20' minimum) with the concrete to function correctly. If we consider the bottom bar in the trench shown as the actual CEE, the connection point at the intersection of the vertical painted bar to the horizontal bottom bar seems tome to be a weak point. . A 90deg bent bar, with at least 24" of bar to bar contact, and then wire tied, would offer a better path for current flow, IMO.

Thoughts on this?

(BTW - the bars will be lifted and fully encased in concrete when poured... not in conctact with the soil, just in case you were worried about that!)


View attachment 7798

Darren, when you state, "will be raised vertically" are you refering to both the vertical and horizontal re-bar, or just the verticall?

I would conscider your idea a better design to have a 90 degree bend and multiple tight band wire to be a better mechanical connection.

 

[gadfly56]

Darren, when you state, "will be raised vertically" are you refering to both the vertical and horizontal re-bar, or just the verticall?

I would conscider your idea a better design to have a 90 degree bend and multiple tight band wire to be a better mechanical connection.

You might want to consider going over to the Fine Homebuilding web site and see what you can find there on proper rebar design. Years ago they had a really excellent article, the gist of which was that when it comes to design, almost everyone gets it wrong. Access to the magazine articles requires a subscription to the web site, but there are a number of "How To" videos on YouTube on rebar produced by them.

 

[infinity]

What size rebar is that?

 

[kwired]

My opinion, connect your GEC to a piece that is minimum 20 feet long and who cares how they have tied to other bars, or even if they installed the rebar correctly, you are the electrician not the footing designer. You will still have a better grounding electrode than if you drove ground rods, even if there is only the one 20 foot piece of rebar embedded in the footing.

 

[petersonra]

My opinion, connect your GEC to a piece that is minimum 20 feet long and who cares how they have tied to other bars, or even if they installed the rebar correctly, you are the electrician not the footing designer. You will still have a better grounding electrode than if you drove ground rods, even if there is only the one 20 foot piece of rebar embedded in the footing.

I am amazed how much time is wasted by people worrying about such a minimally important thing as the average grounding electrode system. Do the bare minimum the code requires and be done with it.

 

[infinity]

So your concern is whether or not the single tie on the crossing of two perpendicular rods is sufficient? If we look at the NEC requirement it doesn't specify what usual steel tie wires are or how they're installed. IMO it doesn't really matter how they're joined, be it by overlap or by perpendicular crossing.

250.52(A)(3) Concrete-Encased Electrode. A concrete-encased
electrode shall consist of at least 6.0 m (20 ft) of either
(1) or (2):
(1) One or more bare or zinc galvanized or other electri-
cally conductive coated steel reinforcing bars or rods of
not less than 13 mm (1⁄2 in.) in diameter, installed in
one continuous 6.0 m (20 ft) length, or if in multiple
pieces connected together by the usual steel tie wires,
exothermic welding, welding, or other effective means
to create a 6.0 m (20 ft) or greater length; or

 

[cadpoint]

My problem with this is where is the 1/2" worth of rod at twenty feet at? It frankly looks like
masonry block mesh screening inverted to be a footer!

 

[infinity]

Are you saying that you don't beleive that this is actually rebar?

 

[cadpoint]

To me the stuff doesn't look any bigger than a pencil and the trench doesn't look wide enough either.
If that's all good so be it.

 

[augie47]

If I may.... ignoring the size of the bar and it's problems as as footer steel.,,, looking through these old eyes it appears we have a piece of rebar driven vertically in the ground and the footer rebar tied to it as it passes by. Am I seeing this correctly ?
If so, I would be interested in how others feel about such an install (assuming the rebar use as footer reinforcement is 100% to building code)

 

[kwired]

To me the stuff doesn't look any bigger than a pencil and the trench doesn't look wide enough either.
If that's all good so be it.

What is in the photo to use as a reference to determine the size of anything?

We have no idea what the width of the trench is, and have no known objects to compare sizes to. Asking the OP what size the rebar is, is acceptable, but telling him what size it is with no supporting evidence is not right.

 

[kwired]

If I may.... ignoring the size of the bar and it's problems as as footer steel.,,, looking through these old eyes it appears we have a piece of rebar driven vertically in the ground and the footer rebar tied to it as it passes by. Am I seeing this correctly ?
If so, I would be interested in how others feel about such an install (assuming the rebar use as footer reinforcement is 100% to building code)

I see no problems here, and the picture is exactly what I see a lot of the time.

The vertical pieces are driven into the ground, not for use as grounding electrodes, the concrete guys could care less about that, they are used both as vertical reinforcement of the concrete and as a place to tie the horizontal bars to for positioning them where they want them in the pour. IMO your GEC needs to tie to a full 20 foot piece of bar, meaning that it can not tie to any of the vertical bars if they are less than 20 feet long, or if they would happen to be above grade when finished.

Some people don't feel this way, and some inspectors would let you tie to a 6 inch piece as long as it is tied "with the usual ties" to at least 20 feet somehow. I can kind of see where that comes from, but if presented with what we see in the picture why not tie to a horizontal bar instead of a vertical bar? It takes pretty much the same effort and removes any doubt of whether or not the vertical piece is acceptable.

 

[infinity]

IMO your GEC needs to tie to a full 20 foot piece of bar, meaning that it can not tie to any of the vertical bars if they are less than 20 feet long, or if they would happen to be above grade when finished.

Some people don't feel this way, and some inspectors would let you tie to a 6 inch piece as long as it is tied "with the usual ties" to at least 20 feet somehow. I can kind of see where that comes from, but if presented with what we see in the picture why not tie to a horizontal bar instead of a vertical bar? It takes pretty much the same effort and removes any doubt of whether or not the vertical piece is acceptable.

The wording in 250.52(A)(3) does not supoport your interpretation. It says that shorter pieces can be tied together to make a 20' piece of rebar.

 

[kwired]

The wording in 250.52(A)(3) does not supoport your interpretation. It says that shorter pieces can be tied together to make a 20' piece of rebar.

I realize that, but as I said, if presented with what is in the OP photo, I would always connect the GEC to a horizontal piece, but if I were an inspector I really don't see how I could make someone move the connection from a vertical piece if they installed it that way.

 

[gndrod]

Foundation rebar

Foundation rebar

My problem with this is where is the 1/2" worth of rod at twenty feet at? It frankly looks like
masonry block mesh screening inverted to be a footer!

I agree. Sure looks like the foundation contractor used No.3 rebar for both vertical and horizontal steel with the exception of the No.4 'painted' and tacked on vertical UFER riser.

Daren,
If this is being done under the IRC code for a footer, the rebar must be No.4 for horizontal rebar and be 3" above hardpan per IRC R403.1.3.1 in the trench. (i.e. 3" wire chairs height spacing) IRC R511.7.1.3 does specify a 24" lap splice wired to the adjoining rebar as you mentioned.

The pictured No.4 stub up does not appear to qualify as a worthy 'continuous' No.4 UFER configuration as specified in the NEC 250.52(A)(3) CEE permitted grounding.

 

[kwired]

I agree. Sure looks like the foundation contractor used No.3 rebar for both vertical and horizontal steel with the exception of the No.4 'painted' and tacked on vertical UFER riser.

Daren,
If this is being done under the IRC code for a footer, the rebar must be No.4 for horizontal rebar and be 3" above hardpan per IRC R403.1.3.1 in the trench. (i.e. 3" wire chairs height spacing) IRC R511.7.1.3 does specify a 24" lap splice wired to the adjoining rebar as you mentioned.

The pictured No.4 stub up does not appear to qualify as a worthy 'continuous' No.4 UFER configuration as specified in the NEC 250.52(A)(3) CEE permitted grounding.

And just what reference to a known sized object is in the photo to determine the size of anything in the photo?

 

[George Stolz]

Ignoring the size of the rebar (which we don't know), I'm with Rob and others on this. There is nothing in the NEC to prohibit a perpendicular lap from forming the connection to the CEE. It shouldn't matter anyway.

 

[kwired]

If this is not 1/2 inch or larger rebar we do not have a CEE. We do not have to use it, and we don't have to have a CEE if there is not one there.

If we still want a CEE for the installation and there is not one there, we can either provide a 20 foot piece of 1/2 inch or larger of our own to put in there, or even just install 20 feet of 4 AWG bare copper in there and then we have a CEE.

 

[gndrod]

And just what reference to a known sized object is in the photo to determine the size of anything in the photo?

The vertical painted rebar appears larger than the attached horizontal rebar at the footer.