Underground Electrical Conduit Depth

Running underground cables in metal conduits approved for buried cables is the most expensive method but also the one requiring the least digging.

Underground electrical conduit depth.

Buried wiring runs that transition from underground to above ground must be protected in conduit from the required cover depth or 18 inches whichever is less to its termination point above ground or at least 8 feet above grade. Cable in any conduit including pvc that is buried at this depth is not in danger of being severed or disturbed by normal digging. Conduits for underground electrical wiring pvc and rigid conduits are typically used when installing underground electrical wiring. You may also run them at a depth of 4 inches under a 4 inch concrete slab.

Low voltage wiring carrying no more than 30 volts must be buried at least 6 inches deep. Where solid rock prevents compliance with the cover depths specified in this table the wiring shall be installed in metal or non metallic raceway permitted for direct burial. Backfill surrounding conduit or cables must be smooth granular material without rocks. Emt and imc conduits should not be used for underground electrical wiring installations.

The national electric code nec sets the required burial depth of electric wire in rigid non metallic conduit such as pvc at 18 inches. At 24 inches you can bury underground feeder cable using pvc conduit to 18 inches below ground only where the wire comes up. At 18 inches you can use thwn 2 conductors inside a continuous length of pvc conduit which protects the wire all the way through the trench to the house. The raceways shall be covered by a minimum of 50 mm 2 in of concrete extending down to rock.