What Is the Minimum Burial Depth for PVC Conduit Under a Driveway?
For a one or two family dwelling driveway used only for dwelling related purposes, the minimum cover is 18 inches for any wiring method, including PVC. For any other driveway, parking lot, street, alley, or road, it jumps to 24 inches. Those two rows in NEC 2023 Table 300.5(A) override the general depths, and they apply regardless of conduit type, voltage, or circuit rating.
Reading Table 300.5(A) correctly
Table 300.5(A) is a grid. The rows are location descriptions and the columns are wiring methods. Column 1 is direct buried cable, column 2 is rigid metal conduit and intermediate metal conduit, column 3 is nonmetallic raceways listed for direct burial without concrete encasement, column 4 is residential 120 volt or less branch circuits rated 20 amperes or less with GFCI protection, and column 5 is circuits for irrigation and landscape lighting limited to not more than 30 volts.
For a general open trench, PVC in column 3 requires 18 inches of cover. That is the number most people already know. Under a one and two family dwelling driveway the row reads 18 inches straight across all five columns, so the driveway does not deepen a normal residential PVC run at all. It does deepen the column 4 shallow branch circuit, which would otherwise be allowed at 12 inches, and it deepens the landscape lighting circuit, which would otherwise be allowed at 6 inches. Under streets, highways, roads, alleys, driveways, and parking lots the row reads 24 inches straight across, which does deepen a normal PVC run.
The distinction between the two driveway rows is ownership and use, not surface material. A driveway at a duplex used only by the residents falls in the 18 inch row. The same slab at a fourplex, a shop, or a commercial building falls in the 24 inch row. Gravel, asphalt, and concrete are treated the same.
What counts as cover and the exceptions that help
Cover is defined in the note to Table 300.5 as the distance from the top of the buried conduit or cable to the top of the finished grade, concrete, or similar cover. It is not measured to the bottom of the trench and not to the top of the slab base course. If the driveway slab is 4 inches thick, that 4 inches counts toward your 18.
Section 300.5(D)(4) requires that a raceway emerging from grade be protected from the point of emergence to a point 8 feet above finished grade, and 300.5(D)(1) requires protection where direct buried cable emerges. Section 300.5(J) requires provisions to prevent damage from earth movement where subject to settlement or frost heave, which is why expansion fittings and S bends at the riser matter in freeze thaw climates. Section 352.44 sets the expansion fitting requirement for PVC based on the expected temperature change and the 0.00003 inch per inch per degree F coefficient in Table 352.44.
One useful relief valve: Table 300.5(A) note 5 permits a lesser depth where the conduit is covered by not less than 2 inches of concrete extending at least 6 inches beyond the underground installation. That is the standard fix when rock or an existing utility makes the required depth impossible. Get it approved before you pour, since the AHJ has the final call under 90.4.