Gabion retaining walls — wire mesh baskets filled with rock — are a popular DIY option for NZ homeowners wanting to manage sloped sections, prevent erosion, or add a rugged natural look to their garden. For walls under 1.5 metres high that retain no more than 1.5 metres of ground, many homeowners can tackle this themselves, but you must check consent requirements with your local council before you start, as rules vary by site and region.
Do You Need a Building Consent?
In New Zealand, retaining walls are covered by the NZ Building Code and managed under the Building Act 2004. Under Schedule 1 exemptions, some low retaining walls may not require a building consent — but this depends on the height of the wall, the surcharge (load) above it, and site-specific conditions such as proximity to boundaries, other structures, or unstable ground.
As a general guide:
- Walls up to 1.5 m retaining no more than 1.5 m of ground may be exempt in many situations
- Walls on steep, unstable, or flood-prone land are unlikely to be exempt regardless of height
- Walls near boundaries or public spaces may require consent even if small
Always confirm with your local council before building. You can also read the guidance on exemptions at MBIE Building Performance. Getting this wrong can cause problems when you sell your home or make an insurance claim.
What Is a Gabion Wall?
A gabion is a rectangular wire mesh cage, typically made from galvanised or PVC-coated steel, filled with rocks or stones. Stacked and tied together, these cages form a gravity retaining wall — one that holds back soil through sheer weight rather than deep footings. They're flexible, drain naturally, and suit NZ's variable climate well, including areas prone to wet winters and ground movement.
Planning Your Gabion Wall
Before you buy anything, spend time on planning:
- Measure the area — note the total length, required height, and how much soil you need to retain
- Check the slope and soil type — loose, sandy, or clay-heavy soils may need additional engineering advice
- Locate underground services — call Dial Before You Dig (0800 248 344) to identify pipes, cables, or drains
- Consider drainage — gabions drain naturally, but you may need a drainage layer or agricultural pipe behind the wall to prevent hydrostatic pressure building up
- Choose your stone — hard, angular rock (such as basalt, greywacke, or schist) works best; avoid soft or round stones that can shift
Tools and Materials You'll Need
| Item | Notes |
|---|---|
| Gabion baskets | Available in various sizes; 1 m × 0.5 m × 0.5 m is common |
| Galvanised spiral binders or clips | For joining cages together |
| Angular fill rock | 100–200 mm diameter is typical |
| Compactor or hand tamper | For base preparation |
| Geotextile fabric | Lines the back of the wall to prevent soil migration |
| Spade, level, string line | For layout and levelling |
| Gloves and safety glasses | Wire mesh edges are sharp |
Gabion baskets and fill rock are available from landscape suppliers and stores like Bunnings and Mitre 10. PlaceMakers can also be a useful source for geotextile fabric and drainage materials.
Step-by-Step: How to Build a Gabion Retaining Wall
1. Prepare the Base
Excavate a level trench at least 150–200 mm deep for your first course of gabions. Compact the base well — a solid, level foundation is critical. For walls over 1 m tall, consider a compacted gravel base for improved drainage and stability.
2. Lay Geotextile Fabric
Line the soil-side of the excavation with geotextile fabric before placing your first gabion course. This prevents fine soil particles from washing through the wall over time.
3. Assemble and Position the First Course
Unfold and assemble your gabion cages according to the manufacturer's instructions. Place them in the trench, check they're level, and join adjacent cages together using spiral binders or clips along all shared edges.
4. Fill with Rock
Fill each cage with your chosen angular rock. Pack the face stones tightly by hand for a neat appearance, then fill the interior more loosely. Avoid overfilling — the lid should close flat. Compact lightly as you go.
5. Close and Stack
Fold down the lid and secure it with binders. For walls with multiple courses, step each course back slightly (around 50–100 mm per course) to improve stability and give the wall a natural batter. Connect each new course to the one below.
6. Backfill and Drainage
Backfill behind the wall in layers, compacting gently. Install agricultural drainage pipe at the base of the wall if needed, directing water away from the structure.
Safety Considerations
Wire mesh edges are extremely sharp — always wear heavy gloves and eye protection. Rock fill is heavy; use safe lifting techniques and get help for large stones. If you're working on a steep slope, assess the risk of slips carefully. WorkSafe NZ has guidance on safe manual handling and working on slopes.
When to Call a Professional
While small gabion walls are DIY-friendly, there are situations where you should engage a qualified retaining wall builder or geotechnical engineer:
- The wall will be over 1.5 m high
- You're on unstable, steep, or flood-prone ground
- The wall is near a boundary, driveway, or structure
- You're unsure about soil conditions or drainage
- A building consent is required
A licensed professional can also help you navigate consent requirements and ensure the wall meets the NZ Building Code. You can find experienced retaining wall builders in your area right here on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
