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The Complete Guide to Retaining Walls: Types, Materials, Drainage & Construction

Retaining walls do much more than hold soil back.

They can turn a sloping backyard into a more usable garden, create different levels, protect garden areas from erosion and help connect landscaping features across a property.

But a retaining wall is also a structure that has to deal with soil pressure, water, ground movement and the weight of anything around it.

That is why choosing a material and building a wall is not simply a matter of deciding what looks good.

At CanLandscape, we have worked on retaining wall projects ranging from straightforward garden-level walls to more challenging sites involving slopes, drainage problems, restricted access and existing landscaping.

Our experience has taught us that the visible wall is only one part of the job. The foundation, drainage, soil conditions, wall design and backfilling all work together.

This guide explains how retaining walls work, the different materials available, common problems, drainage considerations, the construction process and what homeowners should think about before starting a project.

What Is a Retaining Wall?

A retaining wall is a structure designed to hold soil in place where there is a difference in ground level.

Without a retaining wall, soil naturally wants to move from a higher level toward a lower level. A properly designed wall allows a property to have usable changes in level rather than requiring everything to remain on one slope.

Retaining walls are commonly used to:

The wall itself is only part of the solution.

The conditions behind and underneath the wall are just as important.

When Does a Property Need a Retaining Wall?

A retaining wall may be needed when a property has a significant change in ground level that needs to be supported.

For example, a backyard may slope down sharply from the house. Instead of leaving the entire yard on a slope, a retaining wall can be used to create a more practical level area.

Retaining walls can also be useful when renovating an existing garden.

An old garden may have awkward levels, poor use of space or areas where soil is gradually moving downhill. Rather than simply adding new plants or paving, the underlying levels may need to be addressed first.

Retaining walls can also form part of a larger landscape construction project involving:

The important question is not simply whether you need a wall.

It is what the wall needs to achieve and what conditions it will have to handle.

Retaining Walls for Sloping Canberra Blocks

Sloping properties are common in landscaping projects, and a retaining wall can be an effective way to make better use of the available space.

A slope does not automatically mean the entire backyard needs to be flattened.

In many cases, working with the existing levels and creating practical terraces or sections can produce a better result.

A retaining wall on a sloping property may help create:

However, slopes also create challenges.

Water naturally moves downhill, so drainage needs to be considered from the beginning. Soil conditions, access, excavation and the amount of material required can also affect how the wall should be constructed.

This is why we prefer to look at the whole site rather than treating the retaining wall as an isolated feature.

For larger landscaping projects, the retaining wall may also need to work with the overall landscape layout and planting design. Our complete guide to landscape design explains why levels, drainage, access and long-term use should be considered before construction begins.

What Are the Main Types of Retaining Walls?

There is no single retaining wall system that is right for every property.

The appropriate choice depends on factors such as:

Some of the systems commonly considered for landscaping projects include timber, concrete sleepers, masonry and other retaining wall systems.

Blocks and bricks retaining walls in Canberra

Timber Retaining Walls

Timber can be an excellent option for the right application.

It works particularly well in residential gardens where a natural appearance is wanted and where the wall height and site conditions are suitable for the system being used.

Timber can also be relatively quick to install and can integrate naturally with planting, lawns and other garden elements.

One of the main disadvantages is longevity.

Timber is exposed to moisture and can eventually deteriorate. Poor drainage can make this problem worse, and the type and quality of timber used also matter.

We tend to consider timber when:

We don’t view timber simply as the cheaper alternative to every other retaining system.

It needs to be suitable for the job.

Concrete Sleeper Retaining Walls

Concrete sleepers are a popular option where durability, strength and relatively low maintenance are important.

They can work particularly well for sloping properties and larger landscaping projects where a more substantial retaining structure is required.

Concrete sleepers can also provide a clean and structured appearance that suits modern landscapes.

However, the sleepers themselves are only one part of the retaining system.

The posts, foundations, drainage and installation method are equally important.

A strong concrete sleeper does not compensate for an inadequate foundation or poor drainage.

We generally consider concrete sleepers when:

Blocks and bricks retaining walls in Canberra

Block, Brick and Masonry Retaining Walls

Masonry retaining walls can be a good choice where appearance and integration with the property are important.

They can provide a solid, permanent-looking result and can be designed to complement the house and surrounding landscape.

However, masonry should not be selected simply because it looks strong.

Depending on the height and site conditions, the design may need to consider:

A masonry wall still needs to be designed and constructed for the forces it will experience.

Other Retaining Wall Systems

There are other retaining systems that may be appropriate depending on the site, including segmental retaining wall systems and other engineered retaining products.

The important thing is to select the system based on the project rather than choosing a material first and trying to make the site fit it.

Our approach is simple:

Choose the retaining system around the site, not the site around the material.

A system that works perfectly on one property may not be the right solution on another.

Different types of retaining walls in Canberra

How Do You Choose the Right Retaining Wall Material?

The right material depends on more than appearance.

Before choosing a retaining wall system, we consider:

For example, a small garden-level wall may have very different requirements from a taller wall supporting a level area near a driveway or structure.

This is why there is no universal answer to questions such as “Are concrete sleepers better than timber?”

The better question is:

Which system is appropriate for this particular site?

Why Retaining Wall Drainage Is So Important

Drainage is one of the biggest issues we see with retaining walls.

A wall may look strong from the outside, but water building up behind it can create significant additional pressure.

When soil becomes saturated, it becomes heavier and water pressure can act against the wall.

If water cannot drain away properly, the pressure behind the wall can contribute to movement, leaning, bowing or failure.

This is why drainage needs to be considered as part of the retaining wall system rather than added as an afterthought.

Depending on the project, appropriate drainage may include free-draining material behind the wall and a suitable drainage outlet or system.

But there is another important point.

The water needs somewhere to go.

Installing drainage behind a wall without considering the final discharge point does not necessarily solve the problem.

Surface drainage also matters.

The surrounding landscape should be graded so that surface water is not unnecessarily directed toward the wall.

For properties with existing drainage problems, retaining wall work may need to be considered alongside the wider drainage solution. Our landscaping drainage guide for Canberra homes covers this in more detail.

What Causes a Retaining Wall to Lean or Bow?

A retaining wall that starts leaning or bowing is showing signs that something may be wrong.

Possible causes include:

A small amount of movement should not simply be ignored.

The important thing is to identify what is causing the movement.

Replacing the visible wall material without addressing the underlying problem can leave the same issue waiting to happen again.

Other Common Retaining Wall Problems

Leaning and bowing are not the only problems homeowners may encounter.

Other issues include:

In many cases, the visible problem is only the symptom.

For example, if a wall is moving because water is trapped behind it, simply rebuilding the wall without fixing the drainage may not solve the underlying issue.

What Happens When a Retaining Wall Fails?

A retaining wall failure can range from minor movement to a major structural problem.

A failing wall may allow soil to move into lower areas, damage nearby landscaping or affect paths, gardens and other features.

The potential consequences become more significant when there are structures or heavy loads close to the top of the wall.

This is why we recommend dealing with signs of movement early rather than waiting until the wall becomes an obvious safety or structural problem.

If an existing wall is leaning, bowing, cracking or deteriorating, the first step should be understanding why it is failing.

Types of retaining walls in Canberra

What Is Involved in Building a Retaining Wall?

A retaining wall should be planned and constructed as a complete system.

Our typical process starts with understanding the site and continues through to the final landscaping.

Step 1: Assess the Site

Before construction begins, we look at what the wall needs to achieve.

We consider:

The surrounding site matters because a retaining wall does not operate in isolation.

Step 2: Establish Levels

We establish the existing levels and determine the required finished levels.

This is one of the most important parts of the planning process.

A retaining wall changes the way the property works with different ground levels, so incorrect measurements can affect drainage, garden grades and the amount of soil pressure acting on the wall.

We look at both the top and bottom of the wall and how the finished landscape will connect with surrounding areas.

Step 3: Excavate and Prepare the Area

Once the layout and levels have been established, the area is excavated to provide the space required for the selected retaining system.

The foundation area needs to be properly prepared.

A retaining wall is not simply a matter of digging a trench and putting materials into it.

The preparation needs to suit the system being installed and the ground conditions on the site.

Step 4: Install the Foundation, Posts or Footing

The construction at this stage depends on the retaining system.

Where posts are required, they are set out and installed at the appropriate positions and depths.

For masonry and other systems, the structural preparation and footing will be appropriate to that system.

The purpose is to create a stable foundation capable of supporting the wall and resisting movement.

Step 5: Install Drainage

Drainage is incorporated into the retaining wall construction where required.

Appropriate free-draining material and drainage components help prevent water from simply building up against the rear of the wall.

We also consider where the water will discharge.

Drainage is not complete unless the water has a practical path away from the structure.

Step 6: Construct the Retaining Wall

The selected retaining system is then installed according to the requirements of that system.

At this stage, we pay attention to:

The front face is obviously important visually, but what happens behind the wall is just as important.

Step 7: Backfill Correctly

Once the wall and drainage components are in place, the area behind the wall is backfilled appropriately.

Backfilling is another area where shortcuts can cause problems later.

The material, drainage layer and compaction need to be suitable for the wall and site.

A good-looking wall can still perform poorly if the area behind it has not been prepared correctly.

Step 8: Complete the Landscaping

The final stage is establishing the finished levels and completing the surrounding landscape.

Depending on the project, this may include:

We then check the finished levels, drainage and overall appearance of the retaining area.

The goal is not just to finish the wall.

The goal is to make the wall work as part of the complete landscape.

What Should Be Checked Before Building a Retaining Wall?

Before starting construction, we pay particular attention to:

These factors can change the appropriate construction approach.

That is why a retaining wall should be assessed based on the actual property rather than using a one-size-fits-all approach.

Retaining walls drainage installed in Canberra

Can You Build a Retaining Wall Yourself?

Some small, straightforward garden projects may be suitable for an experienced homeowner.

DIY can make sense where the project is low risk, the wall is appropriate for the system being used, the site is straightforward and there are no significant drainage, structural or access issues.

However, the risks increase as the wall becomes taller or the site becomes more complicated.

Professional advice becomes particularly valuable where there are:

Our general rule is simple:

If a mistake is cheap and easy to undo, DIY may make sense. If a mistake could affect drainage, structure, property or safety, get professional advice before starting.

How Retaining Walls Work With Garden Renovations

A retaining wall is often part of a larger garden renovation rather than a standalone feature.

For example, an outdated backyard may have:

In that situation, rebuilding the garden around the existing problems may not produce the best result.

Sometimes the levels need to be changed first.

A retaining wall can help create the structure needed for a new layout, after which lawn, planting, paving, pathways and entertaining areas can be positioned around it.

This is one reason we prefer to understand the whole landscape before deciding exactly what retaining system is required.

Our complete guide to garden renovation explains how we approach existing gardens and why fixing the underlying problems should come before simply adding new features.

How Much Does a Retaining Wall Cost in Canberra?

The cost of a retaining wall depends on the specific project.

Important factors can include:

Rather than repeating all of the pricing information here, we have a separate guide covering retaining wall costs in Canberra.

That page is focused specifically on the cost side of retaining wall projects, while this guide focuses on the types, planning, drainage, construction and practical decisions involved.

How Can Retaining Walls Create More Usable Garden Space?

One of the biggest advantages of retaining walls is their ability to change how a sloping property can be used.

A steep or uneven backyard may have plenty of physical space but very little usable space.

By creating different levels, a retaining wall can help separate areas for:

The aim should not necessarily be to flatten the entire block.

Often, the better result comes from creating practical levels that work with the existing site.

This can make the garden easier to use while also giving the landscape more structure.

What Homeowners Should Not Do to Save Money

The most common mistake we see is focusing too heavily on the visible materials.

Homeowners naturally compare the cost of timber, sleepers or masonry.

But the material is only part of the retaining wall.

Cutting corners on the parts that will eventually be hidden can create much larger costs later.

We would not recommend trying to save money by:

The cheapest wall to build is not necessarily the cheapest wall to own.

If a retaining wall fails, the cost of removing and rebuilding it can be much greater than doing the important work correctly in the first place.

Our Biggest Retaining Wall Advice

If there are only a few things a homeowner remembers from this guide, we would recommend these.

Start with the site, not the material

Don’t decide that you want timber or concrete sleepers before understanding the conditions.

The site should determine the appropriate system.

Take drainage seriously

Water can create substantial pressure behind a retaining wall.

Good drainage is not an optional extra on a project where water is a concern.

Get the levels right

A retaining wall changes the levels of your property.

Think about the finished levels, water movement and what will happen above and below the wall before construction begins.

Consider everything above the wall

A driveway, building, fence, pool, structure or other heavy load near the top can affect the conditions the wall has to handle.

Don’t cut costs on what you can’t see

Foundations, drainage and appropriate backfill may disappear once the job is finished, but they are critical to how the wall performs.

Frequently Asked Questions About Retaining Walls

What is the main purpose of a retaining wall?

The main purpose of a retaining wall is to hold soil where there is a difference in ground level. Retaining walls can also help create usable garden areas, manage slopes, reduce erosion and provide structure for landscaping.

What type of retaining wall is best?

There is no single retaining wall material that is best for every property. Timber, concrete sleepers, masonry and other systems can all be suitable depending on the wall height, soil, drainage, access, appearance, budget and expected service life.

Are timber retaining walls a good option?

Timber can be a good option for suitable residential garden projects, particularly where a natural appearance is preferred. However, timber is exposed to moisture and can deteriorate over time, so correct material selection, drainage and installation are important.

Are concrete sleeper retaining walls better than timber?

Concrete sleepers can offer greater durability and relatively low maintenance, while timber can provide a more natural appearance and may be practical for certain smaller garden applications. The better option depends on the conditions and requirements of the individual site.

Why does drainage matter behind a retaining wall?

Water that becomes trapped behind a retaining wall can increase pressure against the structure. Appropriate drainage helps control water and reduce the risk of problems associated with water buildup.

What causes a retaining wall to lean?

A retaining wall may lean because of excessive soil pressure, water buildup, inadequate foundations, unsuitable construction, poor ground conditions, incorrect design or other site factors. The underlying cause should be identified rather than simply repairing the visible movement.

Can I build a retaining wall myself?

Some small and straightforward garden retaining walls may be suitable for DIY. Taller walls, steep sites, drainage problems, difficult access, significant excavation or heavy loads near the wall can make professional assessment much more important.

Does a retaining wall always need drainage?

Drainage requirements depend on the wall and site conditions, but water management is an important consideration for retaining wall construction. Where water can build up behind the wall, an appropriate drainage solution needs to be considered.

How do I know which retaining wall material to choose?

Start by assessing the wall height, soil, drainage, ground conditions, access, appearance, budget and expected service life. The retaining system should be selected based on the site rather than simply choosing a material first.

How much does a retaining wall cost in Canberra?

Retaining wall costs vary depending on the material, size, excavation, drainage, access, foundations, ground conditions and other project requirements. For detailed pricing information, see our guide to retaining wall costs in Canberra.

Retaining Walls Built Around the Needs of Your Canberra Property

A retaining wall should not be treated as simply a row of timber, sleepers or blocks holding soil back.

The wall needs to work with the ground, water, levels, landscaping and conditions around it.

At CanLandscape, we approach retaining wall projects by looking at the complete site first. We consider the levels, drainage, access, ground conditions, surrounding landscape and the purpose of the wall before deciding on the appropriate construction approach.

Whether you are creating a more usable sloping backyard, replacing a failing wall or incorporating retaining into a larger garden renovation, the goal is the same: build a retaining solution that is appropriate for the site and works as part of the finished landscape.

If you are planning a retaining wall in Canberra or the surrounding areas, contact CanLandscape to discuss your project and the conditions on your property.

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