Hold-down bolts are often used to secure a structural steel column to the concrete floor. Sometimes they are “wet set” as the concrete is being poured. In other cases, they are installed and tie-wired to the rebar in the footing before concrete is poured like in the image.

If the hold-down bolts are tie-wired to a portion of foundation or footing rebar that qualifies as a concrete encased electrode, and done in accordance with 250.68(C)(2), they are permitted to extend the metal structural frame of a building to the concrete encased grounding electrode. A wet set hold down bolt with no intentional connection to the concrete encased electrode cannot be relied upon as a part of the grounding electrode system.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC^® edition of NFPA 70.

2020 Code Language:

250.68(C) Grounding Electrode Conductor Connections.

(2) The metal structural frame of a building shall be permitted to be used as a conductor to interconnect electrodes that are part of the grounding electrode system, or as a grounding electrode conductor. Hold-down bolts securing the structural steel column that are connected to a concrete-encased electrode complying with 250.52(A)(3) and located in the support footing or foundation shall be permitted to connect the metal structural frame of a building or structure to the concrete encased grounding electrode. The hold-down bolts shall be connected to the concrete-encased electrode by welding, exothermic welding, the usual steel tie wires, or other approved means.