Q. What does the Code require in order to use a metal frame of a building as a grounding electrode?
A. The metal frame of a building/structure can serve as a grounding electrode when it meets at least one of the following conditions [250.52(A)(2)]:
• At least one structural metal member is in direct contact with the earth for 10 ft or more, with or without concrete encasement [250.52(A)(2)(1)].
• The bolts securing the structural steel column are connected to a concrete-encased electrode [250.52(A)(3)] by welding, exothermic welding, steel tie wires, or other approved means [250.52(A)(2)(2)], as shown in the Figure.