Retaining Walls
Typically: May require consentHeight and surcharge loads are the key consent triggers
Retaining walls hold back soil and can be significant structural elements. Whether consent is required depends primarily on height and whether the wall supports any surcharge load above it.
General guidance only. This website provides general guidance only. It does not confirm that building work is exempt and does not replace advice from your local council, architect, architectural designer, engineer, planner, licensed building practitioner or other suitably qualified professional. Any exempt building work must still comply with the New Zealand Building Code and any other relevant legal requirements. Full disclaimer →
Schedule 1 exemption: retaining walls up to 1.5m
A retaining wall may be exempt from building consent if:
- →The wall is no more than 1.5 metres in height
- →The wall does not support a surcharge load (such as a driveway, building, or other loaded area above)
- →The wall is not in a situation where failure could damage an adjacent property or building
Even for walls under 1.5m, some councils and geotechnical situations will still require consent. Poor drainage behind retaining walls is a leading cause of wall failure — design this carefully regardless of consent status.
When building consent is required
Consent is required if the retaining wall:
- →Exceeds 1.5 metres in height
- →Supports a surcharge load (driveway, building, slope with a building nearby)
- →Is on a site with known geotechnical issues (slips, expansive soils, etc.)
- →Is a series of walls that together retain a significant height
- →Is adjacent to a boundary where failure could affect a neighbouring property
Engineering input
Any retaining wall over 1.5m, or one in a complex geotechnical situation, should be designed by a structural or geotechnical engineer. Engineering design ensures the wall is sized correctly for the soil type, drainage conditions, and loads. This is required for consent documentation and is good practice even for smaller walls.
Drainage: the critical detail
Retaining wall failures in New Zealand are almost always related to water pressure building up behind the wall. Whether or not your wall needs consent, include proper agricultural drain or equivalent drainage at the base of the wall to allow water to escape. This is non-negotiable for long-term performance.
Frequently asked questions
Can I build a series of small walls to avoid consent?
Council will typically assess a series of interconnected walls as a system, not as individual structures. If the combined retained height exceeds the exemption threshold, consent may still be required. Don't design around the rules — get advice from your council.
Do I need a geotechnical report?
For walls that require consent, a geotechnical assessment is often required, particularly in areas with complex soils, steep slopes, or a history of landslides. Even for smaller walls, a geotechnical assessment is good practice if the ground conditions are uncertain.
What materials can I use without consent?
The exemption doesn't specify a material — it relates to height and surcharge. Timber, concrete block, concrete, or stone walls all follow the same consent threshold. The material affects the structural design, not whether consent applies.
This may require building consent. Council or professional review is recommended before proceeding.
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