What does cover mean in Table 300.5?

Cover is the shortest distance measured in inches between the top of the buried raceway or cable and the top of the finished grade, concrete, or other surface. It is not the trench depth to the bottom of the conduit.

Why does PVC get less cover than direct burial?

Rigid raceways protect the conductors mechanically, so the code allows shallower minimum cover than for an unprotected direct-buried cable. Rigid and intermediate metal conduit get the least required cover because they are the most robust.

Can a concrete slab reduce required cover?

Yes. NEC Table 300.5 notes allow reduced cover where the run is under at least 2 inches of concrete or equivalent, and residential 120 V GFCI-protected branch circuits of 20 A or less also get a reduced minimum. This tool applies the table column you select.

Does this cover over 600 volt circuits?

Yes. Table 300.5 historically covered 0 to 600 V, with over 600 V in Table 300.50. Recent code editions revised the threshold to 1000 V, but the depth values are unchanged in practice. Select the high-voltage option for the deeper requirements.

Is the local utility or AHJ the final word?

Yes. The NEC sets minimums, but the authority having jurisdiction and the serving utility can require deeper burial, warning tape, or encasement. Always confirm the local amendments before trenching.

What is the Underground Conduit Burial Depth Checker (NEC 300.5)?

Looks up the minimum cover from NEC Table 300.5 for direct-buried cable, RMC, IMC, PVC, and nonmetallic raceways under different surfaces such as general earth, vehicular traffic, and under a building, at 0 to 600 V and over 600 V. Runs entirely in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Underground Conduit Burial Depth Checker (NEC 300.5)

Name: Underground Conduit Burial Depth Checker (NEC 300.5)
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Trench too shallow and you fail inspection or risk a strike; trench too deep and you waste labour. This checker reproduces NEC Table 300.5, which sets the minimum cover for underground wiring by method, surface condition, and voltage. Pick the three inputs and it returns the code minimum in inches.

Understanding NEC Table 300.5

NEC Article 300.5 and its table are the go-to reference for any underground installation. The table organises minimum cover requirements into a grid: columns represent wiring methods, and rows represent surface conditions above the burial. The cover value is the distance from the top of the raceway or cable to the finished grade — not the trench depth to the bottom of the conduit.

How it works

The NEC organizes minimum cover into columns by wiring method and rows by surface condition. The deeper the method needs protection, the greater the cover. The key column values for 0 to 600 V are:

                              Direct  RMC/IMC  PVC/other
                              bury    metal    nonmetallic
General earth                  24       6        18
Under 4 in concrete (resid)    18       6        12
Under road / vehicular         24      24        24
Under a building                0       0         0  (in raceway only)
1-/2-family driveway           18      18        18
GFCI residential branch ≤20A   12       6         6

Over 600 V runs require deeper cover (for example 30 inches direct-buried under general earth). This tool returns the matching cell for your selected method, surface, and voltage.

Why different methods get different depths

The rationale behind the depth differences is mechanical protection. A direct-buried cable is the most vulnerable: only the cable’s own jacket and insulation protect the conductors, so 24 inches of earth above it provides a buffer against digging. Rigid metal conduit (RMC) and intermediate metal conduit (IMC) offer substantial crush resistance, so the minimum cover drops dramatically to 6 inches under general earth. PVC conduit is lighter and less rigid than metal, so it gets an intermediate requirement of 18 inches under earth but still less than direct burial.

Under roads and vehicular traffic areas, the dynamic loading from vehicles overrides the mechanical-protection advantage of rigid conduit, and all methods converge to 24 inches.

Worked examples

Scenario 1 — PVC (Schedule 40) feeder from panel to outbuilding, under a lawn: Surface is general earth, voltage is 240 V (below 600 V threshold), wiring method is PVC nonmetallic raceway. Minimum cover = 18 inches from top of conduit to grade. Trench depth must therefore be at least 18 inches plus the outside diameter of the PVC.

Scenario 2 — Direct-buried UF-B cable for a residential garden circuit, GFCI protected at 20 A, 120 V: This qualifies for the reduced GFCI residential branch circuit exception. Minimum cover = 12 inches for direct-buried cable under this condition, compared with 24 inches without GFCI protection.

Scenario 3 — RMC running under a concrete-paved driveway of a single-family home: Surface condition is 1- or 2-family residential driveway, wiring method is RMC/IMC. Minimum cover = 18 inches — the same whether it is direct buried or RMC under a residential driveway.

Scenario 4 — Any method crossing under a public road: Regardless of wiring method, cover must be at least 24 inches under roads subject to vehicular traffic.

Practical installation checklist

Measure cover from top of conduit to top of finished grade, not to the bottom of the trench.
Add the outside diameter of the raceway or cable to the minimum cover to get the minimum trench depth.
Install warning tape 12 inches above any underground run in general earth — it is not required by NEC Table 300.5 itself but is standard best practice and required by many utilities and local amendments.
Check with your local AHJ (authority having jurisdiction) and the serving utility — both frequently require depths beyond the NEC minimums.
For runs under a building, a raceway is required even if it would otherwise qualify for direct burial; the 0-inch cover value in the table means the run is inside a building’s footprint, not that no protection is needed.