Underground Wiring and Burial Depth (NEC 300.7, formerly 300.5): Cover Depths, Driveways and Protection Where It Comes Up

Tsai Electro is an independent learning site. Not affiliated with TDLR, PSI or NFPA. We explain the ideas in our own words and do not reproduce NEC text. Check every rule and table value in your own 2026 NEC, call 811 before you dig, and follow your supervisor and the local inspector.

What “cover” means

Cover is the distance from the top of the cable or raceway to the finished grade, not the depth of the trench. A 2 in conduit in an 18 in trench does not have 18 in of cover. Cover is measured to the top of the conduit, so the trench has to be deeper by at least the conduit’s outside diameter, plus any bedding under it.

This page is about depth and protection in the ground. For how many conductors fit in the conduit, see our raceway and conduit fill guide.

Minimum cover for circuits up to 1,000 V AC or 1,500 V DC

The values below summarize common rows of the NEC minimum cover table (NEC Table 300.7(A)). They are not a full installation spec: the location rules, permitted wiring methods and table notes still apply. Other rows, such as under a concrete slab or at airport runways, and the table notes, such as the one for solid rock, can change the required cover, so open the full table in your 2026 NEC. The 2026 NEC moved the underground rules from 300.5 to 300.7, so use the new number when you practice lookups for the Texas exam. Read both the location row and the column for your wiring method or circuit. Special allowances for residential GFCI-protected circuits and low-voltage landscape lighting apply only when all conditions are met. Do not select the shallowest depth just because the circuit qualifies by voltage or GFCI protection. Check the wiring method, the applicable table notes and the full 2026 NEC requirements first. For a burial-depth question, work in this order: (1) identify the location, such as a yard or a driveway; (2) identify the wiring method, such as direct-buried cable or PVC conduit; (3) check whether the circuit qualifies for a special allowance, such as a GFCI-protected residential branch circuit; and (4) read the table notes that apply before you pick the minimum cover. If the question asks for trench depth instead of cover, add the outside diameter of the conduit or cable and any bedding.

Location	Direct-buried cable	Rigid or intermediate metal conduit	Nonmetallic raceway listed for direct burial without concrete encasement	Residential 120 V branch circuit, GFCI, 20 A or less OCPD	Landscape and irrigation control, 30 V or less
Most locations	24 in	6 in	18 in	12 in	6 in
Under a one- or two-family dwelling driveway or outdoor parking area used only for dwelling-related purposes	18 in	18 in	18 in	12 in	18 in
Under streets, highways, roads, alleys and commercial parking	24 in	24 in	24 in	24 in	24 in
Under a building	0 in minimum cover; cables generally need a raceway that extends beyond the outside walls, with specific exceptions for qualifying Type MC and Type MI cable	0 in	0 in	0 in minimum cover; cables generally need a raceway that extends beyond the outside walls, with specific exceptions for qualifying Type MC and Type MI cable	0 in minimum cover; cables generally need a raceway that extends beyond the outside walls, with specific exceptions for qualifying Type MC and Type MI cable

Underground cables and conductors under a building generally must be in a raceway that extends past the building’s outside walls. Type MC and Type MI cable each have their own specific exception with their own conditions, so a direct-burial rating alone does not permit cable under a building without a raceway. Check the conditions of each exception in 300.7, and in Article 332 for Type MI cable, before you omit the raceway. The 0 in cover entry does not waive these wiring-method rules, and it does not permit any other cable to be buried directly under a building.

Protection where wiring leaves the ground

• Rising out of the ground. Direct-buried conductors and cables that come up from grade must be protected by an enclosure or raceway that extends at least 8 ft above finished grade and, below grade, down to the required cover depth or 18 in, whichever is less (NEC 300.7). Where the riser is subject to physical damage, use a wiring method the NEC permits for that exposure, such as Schedule 80 PVC or rigid metal conduit, and check that the raceway and fittings suit the installation.
• Warning ribbon. Direct-buried service conductors and raceways that contain service conductors need a warning ribbon when they are not encased in concrete and are buried 18 in or more below grade. Place the ribbon in the trench at least 12 in above the installation (NEC 300.7(D)(3), formerly 300.5(D)(3)).
• Backfill. Backfill must not contain material that could damage the raceway or cable, such as large rocks, paving material, cinders or sharp debris (NEC 300.7(F), formerly 300.5(F)). Where needed, use sand, selected fill or boards to protect the run.
• Seals. Where moisture entering an underground raceway could contact live parts, seal or plug the raceway at one or both ends. Spare or unused underground raceways entering a building must also be sealed, using materials identified as suitable for the components they contact (NEC 300.7).
• Bushings. Where a direct-buried cable leaves a raceway, a bushing or terminal fitting protects it (NEC 300.7(H), formerly 300.5(H)).

Underground is a wet location

The inside of a raceway buried in the ground is a wet location (NEC 300.7). The conductors inside must be rated for wet locations, such as THWN-2 or XHHW-2. Wire marked only THHN is not rated for a wet location, so it does not belong in an underground run. Many conductors carry a dual THHN/THWN-2 marking. Those may be used underground when the installation stays within the wet-location rating of the THWN-2 marking.

Worked example: how deep to dig

You are running a 2 in Schedule 40 PVC conduit across a yard, not under a driveway. The outside diameter of 2 in Schedule 40 PVC is about 2.375 in.

1. Required cover for PVC in most locations: 18 in.
2. Minimum trench depth = required cover + conduit outside diameter = 18 + 2.375 = 20.375 in (about 20.4 in). This assumes the conduit rests on a suitable trench bottom without additional bedding and that the finished grade does not change. Rounding up to 21 in is a practical choice, not a separate NEC rule; after final grading, confirm at least 18 in of cover over the conduit. Add depth for any bedding under the conduit, and check the cover again after final grading.
3. Check: 21 − 2.375 = 18.6 in of cover over the top of the conduit, which meets 18 in.

If the same run crosses the driveway of a one-family home, the cover there is also 18 in for PVC. Under a commercial parking lot it becomes 24 in, so the trench there is at least 24 + 2.375 = 26.4 in, rounded up to 27 in.

Check yourself

1. Is cover measured to the bottom or the top of the conduit? The top.
2. What is the minimum cover for direct-buried cable in most locations? 24 in.
3. Can you pull THHN-only conductors into an underground PVC run? No. The inside of an underground raceway is a wet location, so the conductors must be wet rated.

FAQ

Sources checked October 2026

• PSI Candidate Information Bulletin, Texas electrician examinations (updated September 15, 2026): https://test-takers.psiexams.com/api/content/bulletin/1682
• NFPA 70, National Electrical Code, 2026 Edition, Article 300