# Can a 20' section of #4 rebar server as concrete-encased electrode ( UFER ) if it is not attached to the rest of the rebar matrix in an on-grade slab

Let's say we have 9'x25' monolithic concrete slab of 5" thickness with a 12" deep by 12" wide "haunch" footer around the perimeter. At 2-1/2" inches below the surface of the slab there is the #4 rebar grid set at 24" on-center. Now, running through one of the 25' footers is a 20' length of #4 rebar that is sitting on chairs that rest directly on the soil. It is encased in the footer but is not attached to the rebar grid above. Can that 20' length of #4 concrete-encased rebar serve as the UFER electrode that has the copper wire attached to it?

• Is there a layer of poly (plastic) between the slab and the underlying bed/subsoil? May 28, 2021 at 20:04
• There won't be a layer of poly between the footer and soil though possibly a layer of poly between the inner "field" of the slab and the stones. Not sure if that would be a waste, since the moisture could enter the slab from the footer. May 28, 2021 at 20:07
• You appear to be asking this question at a point where you could simply connect the two. 20 foot is minimum, so you don't have to, but more is good if available, and if you haven't poured the concrete yet you can tie the stuff together... For that matter, with a typical "haunched footer" you can tie a rebar ring all the way around the footer. 4 chunks of rebar, 4 bends for the corners, plenty of overlap to tie them together... Steel is cheap, concrete is expensive. May 28, 2021 at 21:18
• @Ecnerwal: I am only asking if the minimum 20' length encased down in the footer MUST be attached to the rebar grid that is a couple of inches below the surface, in order to be NEC compliant. That is a Yes/No question. May 29, 2021 at 1:09
• Yes, you can do the absolute bare minimum. / No, it's not the best approach. ;^) May 29, 2021 at 1:59