Ufer Ground (Concrete-Encased Electrode): NEC 250.52(A)(3) Requirements, Rebar Clamp Selection, Conductor Size and Inspection
Sep 10, 2026
Summary: A concrete-encased electrode, commonly called a Ufer ground, is at least 20 ft of 1/2 in or larger electrically continuous steel rebar, or 20 ft of bare 4 AWG or larger copper, encased in at least 2 in of concrete in a footing or foundation in direct contact with earth, per NEC 250.52(A)(3). Since the 2005 NEC, 250.50 requires it to be part of the grounding electrode system whenever it is present in new construction, which means every new building with a footing. The connection to the rebar is made with a clamp listed to UL 467 for concrete encasement or rebar, or by exothermic weld. The grounding electrode conductor to a concrete-encased electrode never needs to be larger than 4 AWG copper, per 250.66(B). No supplemental rod is required when the Ufer is the electrode.
What qualifies
| Element | Requirement, NEC 250.52(A)(3) |
|---|---|
| Rebar option | One or more bare, zinc-galvanized or electrically conductive coated steel reinforcing bars or rods, 1/2 in (13 mm) diameter minimum, at least 20 ft long in total, made electrically continuous by the usual steel tie wire, exothermic welding, welding, or other effective means |
| Copper option | Bare copper conductor 4 AWG or larger, at least 20 ft long |
| Encasement | At least 2 in of concrete, in a foundation or footing that is in direct contact with the earth |
| Not qualifying | Rebar in a slab isolated from earth by a vapor barrier or insulation; epoxy-coated rebar (not electrically conductive coated); rebar in a pier without footing contact |
| Multiple footings | Only one concrete-encased electrode is required to be bonded, even where several exist |
When it is required
NEC 250.50: all grounding electrodes that are present at each building or structure served shall be bonded together to form the grounding electrode system. The exception allows existing buildings where the concrete would have to be disturbed to reach the rebar. In new construction the electrode exists as soon as the footing is poured, so it must be used, and many AHJs require the connection to be inspected before the pour. The Ufer is also the electrode the NEC treats as sufficient on its own: unlike a rod, pipe or plate, it does not require a supplemental electrode under 250.53(A)(2).
Making the connection
| Method | Listing | Notes |
|---|---|---|
| Rebar clamp, bronze, lay-in or set-screw | UL 467, marked for rebar and concrete encasement or direct burial | Fits 1/2 to 1 in rebar (#4 to #8); conductor range 8 AWG to 4/0; the most common method |
| Exothermic weld | Listed mold and weld metal | Permanent; used on utility and industrial work |
| Rebar stub-up with clamp above grade | UL 467 clamp, not necessarily DB | A rebar extension tied to the footing steel and brought up through the slab lets the clamp be accessible; ties must be electrically continuous |
| Irreversible compression connector | UL 467 compression, marked for rebar where used on rebar | Used where the conductor rather than the clamp will be encased |
Whatever the method, the connection point must either be accessible or be listed for encasement. A standard zinc acorn rod clamp is not listed for concrete and is rejected. Bronze clamps rated for direct burial and rebar, like the Conversions Tech lay-in rebar clamps, are listed for the encased connection.
Conductor size to the Ufer
NEC 250.66(B): the portion of the grounding electrode conductor that is the sole connection to a concrete-encased electrode is not required to be larger than 4 AWG copper, regardless of service size. On a 200 A residential service the GEC is 4 AWG copper; on a 1200 A commercial service it is still 4 AWG to the Ufer. Where the same conductor continues to another electrode, size per Table 250.66 for that electrode.
Inspection sequence
- Before the pour: rebar continuity confirmed (tie wire or welds), 20 ft minimum, clamp installed on the rebar and the GEC or a rebar stub-up in place and photographed. Many jurisdictions require this footing inspection.
- Rough-in: GEC run without splices from the service to the clamp (or spliced only by irreversible compression or exothermic weld, 250.64(C)); protected where subject to damage.
- Final: GEC terminated in the service equipment on the listed terminal; if a water pipe electrode exists, it is bonded within 5 ft of entry; no supplemental rod needed for the Ufer.
Quick answers
Is a ground rod still required with a Ufer ground? No. The concrete-encased electrode does not require a supplemental electrode. A metal water pipe electrode, if present, still requires supplementing, which the Ufer satisfies.
What size wire to a Ufer ground? 4 AWG copper is the largest required, per NEC 250.66(B), for any service size.
Can I use a regular ground rod clamp on rebar? Only if it is listed for rebar and for concrete encasement or direct burial; most acorn clamps are not. Use a bronze rebar clamp marked UL 467 DB.
Does epoxy-coated rebar qualify? No. The rebar must be bare, zinc-galvanized or electrically conductive coated.
How long does the rebar have to be? 20 ft total, electrically continuous; it can be several bars tied together.
Conversions Tech stocks UL 467 bronze rebar and pipe clamps, irreversible compression connectors, and ground rods for the rest of the electrode system. See also NEC 2026 grounding changes and the UL 467 listing explainer.
