Grounding electrode system

A ground fault or a lightning surge has to go somewhere, and the earth is where it goes. The grounding electrode system is how your house reaches the dirt. Section E3608 of the 2021 International Residential Code lists what counts as an electrode and adds one firm rule: every electrode present at the building gets bonded together into a single system, not left as separate paths.

Five things qualify. A buried metal water pipe touching soil for 10 feet or more. A concrete-encased electrode, meaning 20 feet of half-inch rebar or 20 feet of 4 AWG bare copper cast into a footing under at least 2 inches of concrete. A ground ring. A driven rod or pipe at least 8 feet long. A buried metal plate. Whichever exist at your house have to be tied together.

Arizona is where the concrete-encased electrode was invented, and the reason is the dirt. Herbert Ufer solved this for the U.S. Army in 1942 while building bomb storage vaults near Tucson and Flagstaff, where the dry, sandy ground read too high for driven rods to work. Concrete holds moisture and spreads contact over a wide surface, so a properly built Ufer holds around four ohms for the life of the foundation.

For example, a rural build in Rio Verde on hauled water has no metal water main to use, so the list gets shorter before the electrician starts. The code also requires a second electrode alongside a lone driven rod unless that rod tests at 25 ohms or less, and in caliche and rock that reading is hard to hit. So the Ufer carries the job and a rod backs it up, spaced at least 6 feet from any other rod. The practical part for an owner: the rebar gets tied and the connection set before the footing pour, and nobody can add it later.