Blog & Insights

How to Choose the Right Retaining Wall Type for Your Property in Dunedin

When it comes to managing slopes, creating usable outdoor spaces, or preventing erosion on your Dunedin or Queenstown property, a retaining wall is often the ideal solution. However, with several different types of retaining walls available, choosing the right one can be challenging. Here's our comprehensive guide to help you make an informed decision.

Understanding Your Site Requirements

Before selecting a retaining wall type, consider these key factors:

• Wall Height: The height of your retaining wall significantly influences which type is most suitable. Timber walls typically work well up to 1.5m, while gabion and concrete block walls can handle greater heights. For walls over 2m, UC pile or engineered solutions may be necessary.
• Soil Conditions: Otago's varied soil types - from clay-heavy soils in parts of Dunedin to the rocky terrain around Queenstown - affect wall design and foundation requirements.
• Drainage Requirements: Areas with high water tables or significant rainfall need walls with excellent drainage capabilities, making gabion walls particularly effective.
• Aesthetic Preferences: Consider how the wall will complement your property's overall appearance and landscaping.
• Budget Considerations: Different wall types have varying costs for materials, engineering, and construction.

Comparing Retaining Wall Types

Timber Retaining Walls

Timber retaining walls using H4 or H5 treated poles and sleepers are a classic choice for New Zealand properties. They offer a natural appearance that blends well with gardens and landscapes. Best suited for walls up to 1.5m in height, timber walls are cost-effective for residential applications and relatively quick to construct. However, they have a finite lifespan (typically 15-25 years) and may require maintenance over time.

Concrete Block Retaining Walls

Concrete block walls provide excellent durability and a clean, modern aesthetic. Available in various colours and textures, they can be designed to complement any architectural style. These walls offer superior longevity and minimal maintenance requirements, making them ideal for both residential and commercial applications.

Gabion Basket Walls

Gabion walls consist of wire mesh baskets filled with stone, creating a visually striking structure that provides excellent drainage. They're particularly well-suited to Otago's landscape, as local stone can be used to create walls that blend naturally with the environment. Gabion walls are highly durable and environmentally friendly.

UC Pile Retaining Walls

For demanding applications requiring maximum structural strength, UC (Universal Column) pile walls are the premium choice. Using steel H-piles driven deep into the ground, these walls can retain significant heights and handle heavy loads. They're commonly used for commercial developments, steep hillside properties, and infrastructure projects.

Making Your Decision

The best retaining wall for your property depends on your specific circumstances. At OCON Group, we provide free site assessments and can recommend the most appropriate solution based on your needs, budget, and site conditions. Our team handles everything from initial design and engineering through to consent submission and construction, ensuring a hassle-free experience.

Get a Free Site Assessment

Building Consent Requirements for Retaining Walls in New Zealand

One of the most common questions we receive from property owners in Dunedin and Queenstown is whether their retaining wall requires a building consent. Understanding the regulatory requirements is essential before starting any retaining wall project.

When Is a Building Consent Required?

Under the New Zealand Building Act 2004 and Building Code, a building consent is generally required for retaining walls that:

• Are more than 1.5 metres in height
• Support a surcharge load (such as a driveway, building, or swimming pool)
• Are within 1.5 times the wall height of any building, boundary, or public space
• Are part of a dam, tank, or pool structure

The Consent Process Explained

If your retaining wall requires consent, you'll need to submit detailed plans and specifications to your local council. In Dunedin, this means applying to Dunedin City Council, while properties in Queenstown, Wanaka, and surrounding areas apply to Queenstown Lakes District Council.

The consent application typically includes:

• Site plan showing wall location relative to boundaries and buildings
• Engineering drawings and calculations prepared by a qualified engineer
• Specifications for materials and construction methods
• Drainage design details
• Geotechnical report (for larger walls or challenging soil conditions)

Resource Consent Considerations

In addition to building consent, some retaining walls may require resource consent under the Resource Management Act. This is particularly relevant for walls near waterways, in heritage areas, or where the visual impact may be significant.

OCON Group's Consent Management Service

Navigating the consent process can be complex and time-consuming. At OCON Group, we offer a complete consent management service. We work with qualified structural engineers to prepare all necessary documentation, liaise with council officers, and manage the entire consent process on your behalf. This ensures your project proceeds smoothly without delays or compliance issues.

Ask About Our Consent Services

The Benefits of Timber Retaining Walls for Residential Properties

Timber retaining walls have been a staple of New Zealand landscaping for decades, and for good reason. When properly designed and constructed using quality materials, timber walls offer an excellent combination of functionality, aesthetics, and value for residential properties in Dunedin, Queenstown, and throughout Otago.

Why Choose Timber?

Natural Aesthetics

Timber blends seamlessly with garden landscapes, creating a warm, natural appearance that complements plants, lawn areas, and outdoor living spaces. Over time, treated timber develops an attractive weathered patina that many homeowners find appealing.

Cost-Effective Solution

For walls up to 1.5 metres in height, timber retaining walls typically offer the best value proposition. The materials are readily available, and construction is relatively straightforward for experienced contractors, keeping labour costs reasonable.

Versatile Design Options

Timber walls can be designed in various configurations - from simple pole and rail constructions to more elaborate cantilevered designs. They can incorporate curves, steps, and integrated garden beds, offering flexibility to suit your landscape design.

Understanding Timber Grades

The longevity of your timber retaining wall depends largely on using the correct treatment grade:

• H4 Treated Timber: Suitable for ground contact but not permanently wet conditions. Ideal for most residential retaining wall applications where good drainage is provided.
• H5 Treated Timber: Designed for ground contact in situations where prolonged wetting is expected. Essential for areas with poor drainage or high water tables.

Maximising Timber Wall Lifespan

With proper construction and maintenance, a quality timber retaining wall can last 15-25 years or more. Key factors affecting longevity include:

• Using appropriately treated timber for the application
• Installing proper drainage behind the wall
• Ensuring adequate foundation depth
• Regular inspections and maintenance

Is Timber Right for Your Project?

Timber retaining walls are ideal for residential garden terracing, boundary walls up to moderate heights, and situations where natural aesthetics are important. For taller walls, heavy-load applications, or maximum longevity requirements, alternative solutions such as concrete block or gabion walls may be more appropriate.

Explore All Retaining Wall Options