Retaining Wall Materials: Get the Right Advice From an Engineer

When you're building a retaining wall, the materials you choose aren't just about looks. They affect everything – from how long the wall lasts, to how safe it is, to whether you'll need to rip it out and start again in a few years. No one wants to spend time and money on a wall that ends up failing a few months down the track, especially in Queensland, where wild weather and tricky soil types can put your landscaping to the test.

That’s why it’s worth slowing down and getting some expert advice before you start digging. Whether it’s a small weekend DIY project or a full backyard transformation, we’re here to help you do it right the first time. Let us break down the different types of retaining wall materials, explain the common traps homeowners fall into and share some advice that can help you save time, stress and potentially thousands in the long run.

Why Material Choice Matters More Than You Think

Retaining walls are more than just a decorative fixture – they hold back soil, manage water runoff and help level sloped blocks. Choosing the wrong retaining wall material or even the right material used in the wrong situation can lead to poor drainage, structural failure and major repair bills. Even the most durable materials, like concrete sleepers, can fail if they’re not selected and installed properly.

Here’s a quick guide to some common retaining wall materials:

Concrete Sleepers

While they’re known to be versatile and long-lasting, not all sleepers are made equal. Concrete sleepers come in different load-bearing strengths utilising different concrete strength and rio bars. Concrete is measured in mPa (megapascal), which indicates how much pressure the sleeper can handle before cracking or failing. Most commercial-grade sleepers are rated at 50-60MPa, but we also stock options from 40–50MPa. Choosing the right sleepers for your wall height, soil type, and load can help you avoid over-engineering and reduce material costs by up to 30%.

Composite Sleepers - TuffPoly & Supersleeper

A newer option made from Fiber Reinforced Polymer. These are the new kid on the block with the sleepers weighing in at less than 8kg per sleeper. They’re low maintenance and won’t rot – but they’re not suitable for high-load applications without engineering advice. Great for the DIYer.

Retaining Wall Blocks

These interlocking blocks are popular for their DIY appeal and aesthetic finish. They’re great for smaller garden walls, but often require structural reinforcement and council approval beyond one metre.

Timber

Great for a natural look and budget-friendly, but not always the best long-term solution. Timber is susceptible to rot and termite damage, especially in wet or poorly drained areas.

No One-Size-Fits-All Solution

Every property is different, with the ideal retaining wall material for your backyard being completely wrong for someone else’s. Factors like slope, drainage, soil composition, nearby structures and your local council requirements all influence what’s suitable. That’s why we never recommend picking materials based on price or looks alone.

The Importance of Engineering

In Queensland, retaining walls over one metre high require certified engineering and council approval. Even walls under one metre may still need approval depending on your location, drainage plans or proximity to boundaries and structures.

While you can check our retaining wall guides that link to helpful government resources for site standards and licensing requirements for some guidance, make sure to check in with a licensed engineer who can give you advice that’s legally compliant and structurally sound.

At Australian Landscape Supplies, we’re here to point you in the right direction. A structural engineer’s job is to assess your site conditions and various aspects that affect your retaining wall and ensure it’s safe and up to code. We’ll help you understand when you need to call one in and what details they’ll need, so your project stays on track and avoids costly issues down the line.

Common DIY Mistakes To Avoid

Here are a few traps homeowners often fall into:

Choosing outdated or short-lifespan materials, like timber, because it’s cheap, without considering longevity or maintenance costs.
Using the same sleeper height across the entire wall, ignoring changes in slope or load.
Skipping proper drainage leading to water pressure build-up and wall failure.
Not checking with the council, and being forced to remove or rebuild a non-compliant wall.
Not allowing for a fence in the footing depths

You don’t have to make these mistakes. With an engineer, you can plan, design and build it right the first time.

How We Can Help

We offer:

Access to a wide range of quality retaining wall materials
Engineering-backed guidance and support
A retaining wall calculator to help you estimate materials with ease
Installation options by licensed professionals if you prefer a hands-off approach

Our team is available by phone, email, live chat or in-store to offer helpful advice based on your specific project needs. Whether you're in the early planning phase or tackling issues mid-build, reach out and let us support your success.

Even a small garden bed wall can benefit from professional insight. With the right prep, many projects can be completed over a weekend – and for the more complex jobs, we’ve got your back.

Get in touch with our team today and let’s build something that lasts.