Hi Tim, great question and definitely not a dumb one! Depth requirements can be tricky.The NEC (National Electrical Code) depth requirements for conduit burial are measured from the top of the conduit to the finished grade.So, to answer your specific question about PVC conduit under a patio: The 6-inch requirement includes the thickness of the concrete.

Here's why: Finished Grade Definition

The "finished grade" in this case is the top surface of the concrete patio after it's poured and cured.

NEC Compliance

You need to ensure that there's at least 6 inches of material (concrete in this case) between the top of the PVC conduit and the final surface of the patio.
Example

Let's say your patio is going to be 4 inches thick:1. You would bury the top of the PVC conduit 6 inches below where the finished surface of the patio will be.
2. The patio concrete is then poured to its 4 inch thickness, the top of the conduit is now 6 inches below the top of the patio.

Important Considerations



Local Amendments

Always check with your local authority (city, county) having jurisdiction. They might have amendments to the NEC that require greater depths.

Compaction

Ensure the soil beneath the conduit is properly compacted before pouring the concrete.

Conduit Support

Properly support the conduit to prevent it from shifting during the concrete pour.

Expansion

If you are running the conduit any significant distance consider using expansion couplings so the conduit doesn't exert pressure on any connection points.

Marking

It's always a good practice to mark the location of the buried conduit (e.g., with caution tape a few inches above the conduit) before pouring the concrete. This helps prevent accidental damage in the future.

In summary, you want the TOP of the PVC conduit to be at least 6 inches below the planned surface of the concrete patio.

Good luck with your inspection! Flag for review