What is the required depth for the grounding wire mesh?

• A. 6 inches
• B. 12 inches
• C. 18 inches where practical
• D. 24 inches

Answer: (C)

Grounding grids are meant to provide a low-impedance path to earth and a durable, reliable connection for the whole site's safety system. Placing the grounding wire mesh at about 18 inches below ground, when feasible, hits a practical sweet spot: it stays below typical surface disturbance and frost, keeps moisture in contact with the conductors for good conductivity, and isn’t so deep that installation becomes overly difficult or costly. The phrase “where practical” recognizes real-world site constraints—like concrete, utilities, rocks, or limited access—and means you should aim for 18 inches whenever you can, but go deeper only if the conditions truly require it.

If the mesh is buried shallower, like six or twelve inches, it’s more vulnerable to surface damage and moisture variations, which can raise impedance. A depth of twenty-four inches, while allowing even more protection, isn’t usually necessary and adds unnecessary effort and cost unless there are specific constraints or frost considerations that justify it.