Underground cable depth calculator
Depth of cover and separation for a buried cable.
Reads AS/NZS 3000:2018. Tables checked 26 Sept 2026.
Try a job 7
Each job fills in example values. Replace them with your values.
- Bury a cable out to a shedThe depth of cover for a sheathed cable in heavy duty conduit.
- Bury a cable under a drivewayThe depth of cover under 75 mm of concrete.
- Bury a cable directThe category and depth for an armoured cable buried direct.
- Cross a water pipeThe separation from a water pipe of DN65 or less.
- Run a cable beside a gas pipeThe separation from a gas service.
- Bury a cable near an earth electrodeThe separation a conductive enclosure needs from the electrode.
- Run a conduit under a slabThe cover a conduit needs within a building.
Inputs
Worked example with the default inputs. The live calculator replaces it when the page loads.
- Cable type
- Insulated and sheathed conductors
- Method of protection
- Buried direct, no enclosure
- Location
- Elsewhere, external to a building
- Surface covering
- No covering, or concrete under 75 mm
- Nearest other service
- No other service nearby
- Near an earthing electrode
- No
Minimum depth of cover
500mm
- Wiring system category
- B
- Marker tape depth
- 250mm
- Bedding and cover material
- 50mm
This result is a design aid. Verify it against the current standard.
Calculation steps
- Wiring system categoryB
AS/NZS 3000:2018 Table 3.5
- Minimum depth of coverResult500mm
AS/NZS 3000:2018 Table 3.6
- Marker tape depth250mm
AS/NZS 3000:2018 Cl 3.11.4.5
- Bedding below and cover above50mm
AS/NZS 3000:2018 Cl 3.11.4.2
- General spacing from other services100mm
AS/NZS 3000:2018 Table 3.7
About this calculator
How this is calculated
The tool gives the rules for a buried cable. It reads Section 3 of AS/NZS 3000:2018. It does not size the conductor.
- Category. You pick the cable type and the enclosure. The tool finds the wiring system category from Table 3.5.
- Depth of cover. It reads the minimum depth of cover for the category, the location and any concrete covering from Table 3.6.
- Marker tape. It gives the depth for the marker tape (Cl 3.11.4.5).
- Bedding. It gives the bedding below and the cover material above the cable (Cl 3.11.4.2).
- Separation. It gives the spacing from other services (Table 3.7). You can pick a gas, water, drainage or telecommunications service.
- Protection. For category B it names the additional mechanical protection (Cl 3.11.4.3).
| Step | Table or clause | What it decides |
|---|---|---|
| Category | Table 3.5 | The wiring system category |
| Depth of cover | Table 3.6 | The least cover |
| Marker tape | Cl 3.11.4.5 | The tape depth |
| Bedding | Cl 3.11.4.2 | The bedding and cover material |
| Separation | Table 3.7 | The spacing from other services |
Worked example
- Insulated and sheathed cable buried direct, outside a building. The tool gives category B. The minimum depth of cover is 500 mm. The marker tape sits at 250 mm. The bedding and cover is 50 mm. Category B also needs mechanical protection above the cable.
Limits
- The tool reads AS/NZS 3000. It does not read the rules of the network company or the council.
- It does not size the cable. Use the cable size calculator for the conductor.
- The form has a field for a cable near an earth electrode. Read the clause for that case.
See also: Underground cables and civil interfaces, Voltage rise on a long rural PV run and Voltage drop.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
What does the underground cable tool do?
The tool reads the wiring system category for your cable type and method of protection. It then reports the minimum cover depth for the location and surface covering. It also reports the bedding depth, the marker tape depth and the separation from another underground service.
Which tables does the result come from?
The category comes from AS/NZS 3000:2018 Table 3.5. The depth of cover comes from Table 3.6. The separation comes from Table 3.7. Bedding, mechanical protection and marker tape depth come from Clauses 3.11.4.2, 3.11.4.3 and 3.11.4.5.
How deep must a buried cable be in New Zealand?
It depends on the category and the surface. A Category A or B system elsewhere than a building needs 500 mm of cover with no concrete above, or 300 mm under poured concrete of at least 75 mm. A Category C system needs 50 mm.
What does Category B mean for the trench?
Category B needs additional mechanical protection above the cable. The tool reports the rule. The protection sits no more than 75 mm over the wiring system and is at least 150 mm wide. It overlaps each side by at least 40 mm. Bedding is 50 mm of friable soil or sand.
Why is a combination marked as not permitted?
Table 3.5 marks some cable and enclosure pairs NP. An example is unsheathed conductors buried direct in soil. The tool reports the combination as a fail and gives no depth. Choose another enclosure or another cable type.
Clauses and tables this tool reads
- AS/NZS 3000:2018 Cl 3.11.4Underground installation requirements
- AS/NZS 3000:2018 Cl 3.11.5Distance to other services underground
- AS/NZS 3000:2018 Table 3.5Underground wiring system categories by cable type and method of protection
- AS/NZS 3000:2018 Table 3.6Underground wiring systems minimum depth of cover
- AS/NZS 3000:2018 Table 3.7Minimum separation of underground services
Every clause and table, with how each was verified
Tables last checked on 26 Sept 2026.
Related tools
- Segregation and separation checkerCheck what may share an enclosure and the separation.AS/NZS 3000
- Maximum circuit length calculatorLongest run that voltage drop and the fault loop allow.AS/NZS 3000AS/NZS 3008.1.2
- RCD selection calculatorCheck if an RCD is required and test the trip time.AS/NZS 3000Electricity (Safety) Regulations 2010
Was this useful?
A question, or a value that looks wrong? Contact us.