Can I build a retaining wall myself?

If the wall is under 1.5 metres, does not support a surcharge load, and does not require consent, you can build it yourself. However, even small retaining walls can fail if built poorly, causing erosion and damage. For any wall requiring consent, an LBP must build or supervise the work.

How much does a retaining wall cost in NZ?

Timber retaining walls cost $300 to $600 per square metre of face area. Concrete block walls cost $500 to $900 per square metre. Engineered concrete walls cost $600 to $1,200+ per square metre. Add engineering design fees ($2,000 to $5,000) and consent fees ($1,500 to $4,000) for consented walls.

NZ Regulations

Do You Need Building Consent for a Retaining Wall in NZ?

When building consent is required for retaining walls in New Zealand. Covers height limits, surcharge loads, engineering requirements, and LBP obligations.

Retaining walls are a common feature of New Zealand properties, particularly on sloping sites. Whether you need a building consent depends primarily on the wall's height and what it supports. Getting this wrong can create safety hazards and legal problems.

When Consent Is Not Required

Under Schedule 1 of the Building Act 2004, retaining walls generally do not need consent if they are no more than 1.5 metres high (measured from the lowest adjacent ground level to the top of the wall) and do not support a surcharge load. A surcharge load means anything that adds weight above the wall — a driveway, a building, another retaining wall, or heavy landscaping. If the wall supports only garden soil with no additional load, it may be exempt.

When Consent Is Required

Building consent is required when the retaining wall is more than 1.5 metres high, when the wall supports a surcharge load regardless of height, when the wall is close to a property boundary and affects neighbouring properties, when the wall is in a natural hazard zone (earthquake, landslip, flood), or when the wall supports or is part of a building. Stacked retaining walls (tiered walls) are assessed based on the total retained height, not individual wall heights.

Engineering Design Requirements

Retaining walls that require consent generally need an engineering design. A Chartered Professional Engineer (CPEng) designs the wall considering soil conditions, drainage, surcharge loads, seismic forces, and wall type (timber, concrete block, concrete, gabion). The engineering design is submitted with the building consent application and the wall must be built exactly to the design.

Drainage Behind Retaining Walls

Proper drainage is critical for retaining wall performance. Water pressure behind a retaining wall is the most common cause of failure. The design should include drainage aggregate, filter fabric, and a drainage pipe at the base to direct water away. Even for exempt walls, inadequate drainage will cause failure over time. If the drainage connects to a stormwater system, a registered drainlayer may be required.

LBP and Restricted Building Work

If your retaining wall requires a building consent, the construction is classified as restricted building work. It must be carried out or supervised by a Licensed Building Practitioner (LBP). The LBP provides a Record of Work confirming the wall was built in accordance with the consent and engineering design. This documentation is essential for the Code Compliance Certificate.

Key Takeaways

Retaining walls up to 1.5 metres high with no surcharge load may be exempt
Walls over 1.5m or supporting a surcharge load require building consent
An engineering design is typically required for consented retaining walls
Drainage behind the wall is critical — failure to drain causes wall collapse
Consented retaining walls are restricted building work requiring an LBP

Frequently Asked Questions

A surcharge load is any weight or force acting on the ground above the retaining wall. This includes: a driveway or parking area, a building or structure, another retaining wall above, heavy landscaping or fill, and vehicle traffic. If any of these are present, the wall likely requires consent regardless of height.