You’ve considered building retaining walls in your garden, but you don’t know where to start. What type of garden retaining wall should you build?
How do you choose the right one for your garden?
Do you need council consent?
This guide will tell you everything you need to know about retaining walls in gardens, from why you should use them in your garden, to the different types of retaining walls available, to tips on building the perfect wall for your needs. You’ll also find tips on maintaining and repairing your wall.
So whether you’re looking to protect your garden from erosion, or simply want to add some extra curb appeal, the Ultimate Guide to Retaining Walls in Gardens has you covered.
People often have challenges with garden retaining walls because they are not sure which wall best suits their garden.
Others might not understand the different types of retaining walls that are available and how each wall can benefit their specific garden. Others may not be sure what size or type of wall they need, or if they even need a retainer wall at all.
Council consent can also be a challenge, as you may not know which retaining walls in gardens require council approval.
And finally, some people struggle with the actual building process of a retaining wall, not knowing how to start or what steps to take.
This guide will help you overcome these challenges and more so that you can build the perfect retaining wall for your garden.
We’ll cover everything, from the different types of garden retaining walls available to the steps involved in building one, to tips on maintaining and repairing your wall.
If what you are looking for is not in this article you will find more info on our retaining walls for gardens page.
So whether you’re a first-time builder, homeowner or an experienced pro, this guide has you covered. Let’s get started!
Why use Retaining Walls in Gardens?
Retaining walls are an important part of any garden, as they can help to prevent soil erosion and protect your plants from being washed away in heavy rains.
They can also be used to create terraces or raised beds, which can make your garden more accessible and easier to maintain. In addition, retaining walls can add visual interest and appeal to your garden.
Soil erosion prevention
Soil erosion is the most common reason for installing retaining walls in gardens.
Heavy rains can quickly wash away soil, not only causing damage to your garden but also leading to potential safety hazards.
A retainer wall can help to prevent this by holding the soil in place and preventing it from being washed away.
Raised beds and terraces
Walls can be used to create level terraces and raised garden beds.
This can be especially useful if you have a sloping garden, as it can help to level out the terrain and make your garden easier to navigate and maintain.
A terrace is often used to give extra space allowing for a level lawn. And by using retaining walls to create terraces, you can also maximise the space on your property by using different levels to organise your garden.
Raised garden beds are also a great way to maximise the use of your space, as they allow you to grow plants in areas that would otherwise be too awkward to garden in.
Accessibility and ease of maintenance
Retaining walls with the use of steps can also make your garden more accessible, as they can provide a level surface to walk on.
In addition, retaining walls can help to make your garden easier to maintain, as they increase the height, making gardening a lot easier on the back.
Visual interest and appeal
Finally, retaining walls can also add visual interest and appeal to your garden.
With a variety of shapes, sizes and colours available, you can find a retaining wall that will perfectly compliment your garden design.
What are the Different Types of Retaining Walls in Gardens?
There are a variety of different types of garden retaining walls available on the market, each with its unique benefits.
It’s important to choose the appropriate wall type for your garden. This will help ensure that your wall is effective, visually appealing and long-lasting.
Concrete Retaining Walls in Gardens
Reinforced concrete walls are either cast in situ using formwork or sprayed concrete. They can be relatively expensive but are the longest-lasting of most retaining walls if built properly.
In most cases, the wall will require an engineer’s design.
The beauty of a concrete wall is that it can be built in any size or shape to suit your garden and home design.
Concrete walls are often used in tight areas as they do not require heavy machinery to construct them.
They can be rendered, painted or cladded in stone or tiles to give the required finish.
Concrete Sleeper Retaining Walls
Concrete sleeper retaining walls are made of pre-cast concrete sleepers. They are one of the cheapest types of garden retaining walls and can be easily installed by a DIY enthusiast.
Concrete sleepers are a great choice for retaining walls as they are incredibly strong and durable. They are also low-maintenance and require no painting or staining.
Concrete sleepers can be manufactured in a variety of styles to resemble other materials. The most common are standard-coloured concrete, timber finish, tiles, slate, and stone.
Most manufacturer’s specifications allow for engineering within the design.
Reinforced Concrete Block Retaining Walls in Gardens
Reinforced concrete block walls are made of hollow concrete blocks that are filled with reinforced concrete.
They are a popular choice for garden retaining walls as they are relatively easy to construct by a qualified tradesman and can be built in most sizes and shapes. They are often used in tight areas.
Concrete blocks come in a variety of colours and textures to the face.
Standard grey blocks are often used when a coloured render or a rendered and painted finish is required.
You can also use a reinforced concrete block wall as a substrate for tiles and stone to adhere to.
In most Australian states, reinforced concrete block walls require an engineer’s design. If the wall is more than 1 metre tall, it will almost certainly need an engineer’s design in Australia.
Dry Stacked Concrete Block Retaining Walls
Dry-stacked concrete block retaining walls are made of solid concrete blocks that are stacked on top of each other without the use of mortar.
They are a popular choice for garden walls as they are easy to construct and can be built in most sizes and shapes and are great for the home handyman.
They do not require reinforcing or a concrete footing in most cases and are great for walls up to 1 metre as the manufacturers have allowed for engineering in their specifications.
For larger walls check with a supplier or you may require an engineer to design the wall for very large walls.
Timber Retaining Walls in Gardens
Timber walls are a great choice for gardens, as they are relatively inexpensive and easy to install. However, they are not as durable as concrete or stone walls and will require regular maintenance.
Timber garden retaining walls can be constructed using a variety of different timbers, the most common being treated pine, timber railway sleepers or different hardwood varieties.
Timber walls are required to be designed by an engineer when they are over 1 metre in height in most states of Australia. You should check your local council’s regulations though.
The longest-lasting timber retaining walls are made from recycled railway sleepers that are in good condition.
These old sleepers used to be treated with creosote which protects them from rot and insects for many decades.
Brick Retaining Walls in Gardens
Brick walls are a popular choice for gardens as they are durable and easy to maintain. However, they are also one of the more expensive retaining wall options.
Bricks can be used to create any shape or size wall and come in a variety of colours and textures.
In most cases, brick walls require a reinforced concrete footing and are built with reinforced concrete brick columns. This has become the norm when building brick retaining walls in gardens.
Brick walls should be designed by an engineer when they are over 1 metre in height in most states.
Stone Retaining Walls in Gardens
Stone walls are among the most popular types of retaining walls in gardens and for good reason.
They are incredibly sturdy and can freely move without cracking, which is a negative for other walls. In addition, stone walls add a touch of elegance and sophistication to any garden.
There are two main types of stone walls: dry-stacked and mortared.
Dry-stacked walls are the more popular of the two and are made of stones that are stacked in a bonded pattern on top of each other without the use of mortar.
This type of wall is cheaper and easier to build than a mortared wall.
They are great for the home handyman as they can require minimal drainage and do not require engineer designs under 1 metre in height in most states.
Mortared stone walls are laid in mortar, which can give them an elegant and classy look. However, mortared walls are also more expensive and more difficult to build.
Rock Retaining Walls in Gardens
Rock walls are a great choice for those who want a natural look in their garden.
They can be made of different types of rocks, such as granite, sandstone, basalt, bush rock or limestone and are usually dry stacked with machinery due to the large sizes of the rock.
Rock walls are incredibly sturdy and do not require any type of reinforcement or concrete footings.
Drainage is not mandatory although it is a good idea to use drainage to redirect water on larger garden walls.
Gabion Walls
These walls have become very trendy in recent years with the addition of other materials such as timber seating or frames and lighting within.
Gabion walls are wire mesh or steel baskets filled with stone or river pebbles. This type of wall is very popular because it is easy and inexpensive to build, and great for DIY.
They do not require concrete footings and can be built without drainage, although it is a good practice to direct water away from any wall.
How to Choose the Right Type of Retaining Wall for your Garden
There are a few things to consider when choosing the right type of retaining wall for your garden. The most important factors to consider are
- The height of the wall
- Whether you want to match any existing materials used in other walls, fences or your house.
- Whether you can get large machinery to the area of the wall to be built
- Do you want to build the wall yourself?
- Longevity
The height of the Retaining Wall
All walls over 1 metre in height must be designed by an engineer and receive your local council’s approval in most states of Australia. (some materials such as concrete sleepers are pre-engineered to a certain height and loading)
In some states, it is less than this and we discuss this further down in this article.
For walls under 1 metre, all of the materials previously discussed are suitable.
However, for walls over 2 metres due to the cost per m2 ratio and engineering factors there are only 2 walls that we would recommend;
- Rock walls and
- Reinforced concrete walls
You can use other materials by stepping back one retaining wall from another.
This is commonly referred to as terracing, think the same as a rice field on a mountainside.
Matching Existing Materials to your Garden Retaining Wall
This is more important for some people than others and will also be influenced by the budget you have to work with.
If you are trying to match other materials used in your garden or house, such as render, stone or timber, then this can be easily achieved with any of the walls we have discussed.
However, if you are looking to match a certain type of brick from the 80’s or stone that there is a limited supply of you may find it easier to use a different material and make a feature of it.
Large Machinery Access
This is a big consideration when deciding on the material to use.
If you want to use a rock wall but the only way to get the rock to the site is by hand then this may not be the most suitable solution for you.
Sometimes it can be possible to get large machinery into difficult places with careful planning and the use of temporary access or a “hole in the fence”.
This is a catch-22 situation as most of the time we need to backfill the wall with machinery.
You can often sneak a bobcat up the side of a house to backfill a wall. You may not be able to get a 20-tonne excavator up there if that’s what’s required for the wall you have chosen.
DIY or Professional Build
This is a consideration for a lot of people and will come down to your skill set and the budget you have available.
The retaining walls that are suited to a DIYer with minimal experience are
- Stone walls
- Gabion walls
- Dry stacked concrete block walls
The retaining walls that are suited to a DIYer with handyman experience are
- The 3 walls above
- Timber retaining walls
- Concrete sleeper retaining walls
- Rock walls (may need to have a licence for the excavator)
If you are not comfortable with using power tools, working with concrete or lifting heavy objects then we would not recommend building your own wall. Sit back and let a Tradie do it for you.
Longevity
This is an important consideration when choosing a retaining walls in gardens.
If you want the wall to last for more than 30 years then we would recommend using a reinforced concrete wall, recycled timber sleepers or a rock wall.
All of the other walls have a life expectancy of 10-20 years depending on the quality of the materials and how well it is built.
Is Council Consent Required for Retaining Walls in Gardens
Most people are unaware that they may need council consent to build retaining walls in gardens.
This is because the main purpose of a retaining wall is to support earth, and therefore the wall itself is considered to be part of the supporting structure.
- If the wall collapses, as the property owner you may be liable.
- If the wall was built without council consent when it was required, you will unfortunately not be insured against damage to your property or others.
- If the wall injures a person you may be prosecuted in a court of law.
For this reason, it is very important to make sure that you get council consent before you start work on retaining walls in gardens that are over the recommended specifications set by the local council.
Following are the basic conditions for each state of Australia on whether you are required to obtain council consent to build a retaining wall on your property.
For a full list please see the local council in your area as individual councils can vary within a state.
Queensland
You do not need council consent to build a retaining wall if the wall is
- less than one (1) metre high
- further than 1.5 metres to a building/structure or another retaining wall
- only supports the soil behind the wall, nothing above eg driveways or other structures
- combined wall and fence height are less than 2 metres
- not part of a pool fencing
The Queensland State Government has produced a helpful guide on building retaining walls which can be found at https://www.qld.gov.au/buildings/home-improvement/retaining-walls/.
New South Wales
Council consent is required in NSW to build retaining walls in gardens if all of the following are not fulfilled; there are more conditions you should check with your local council
- not be cut or filled more than 600mm below or above the existing ground level
- be at least 1m from each boundary
- be separated from any retainer wall or other structural support on the site by at least 2m, measured horizontally
- be located at least 1m from any easement, sewer main or water main
Victoria
Local councils may be different you should check with your council about other regulations that may apply to your situation but basically;
- You will need council approval to build a retaining wall that is higher than 1 metre (1000mm) if:
- the wall is on residential land and next to a road or footpath; or
- the wall is part of other work on the site.
Tasmania
Hobart council suggests that any retaining wall located within 1.5 metres of any boundary that retains a difference in the ground level of 1 metre or more may require planning approval.
South Australia
Council approval for a new retaining wall is required for all State or Local Heritage Places/Areas. It is also required for:
- Retaining a difference in ground levels exceeding 1m
- If the wall is forming part of a fence or safety barrier for a swimming pool or spa.
- A fence or retaining wall combination greater than 2.1 metres in height
- A wall is required to enable other development (e.g. retaining is required to construct a garden shed)
Western Australia
Development approval is required for all commercial and some residential properties, you should check with your local council.
A council building permit is required if;
- You need to retain more than 0.5 metres in height
- The wall is associated with other building work
- The structure affects other land that requires consent.
Northern Territory
As a general rule, you will need council consent if your wall is:
- Over 1 meter high (measured from the ground up)
- Is built on or next to a road, footpath or nature strip; or
- Retains soil that is deeper than 600mm or 1/2m, then you will need approval from your local council before building.
If your wall doesn’t meet any of the above criteria, then you will still need to check with your local council to see if they have any specific regulations around retaining walls in your area.
7 Tips for Building Perfect Retaining Walls in Gardens
- Top of footings below ground level – It is good practice to have the base of the wall where it sits on the top of the footing at least 100mm below ground level. Often the ground level gets changed and there is nothing worse than seeing the footing out of the ground.
- The top of the wall is above the backfill level – When the first heavy rain arrives you don’t want your topsoil washed over the wall. Your backfill should not be level either, rather falling to either end of the wall’s length.
- Walls should never lean away from retained soil – most walls lean into the retained soil but walls that are built plumb, ie reinforced concrete blocks should not be built out of plumb through bad workmanship and lean out.
- Always use adequate drainage – a lot of walls are self-draining and this is good, although it is good practice to still use drainage so the water doesn’t come through the wall and sit on the area in front of the wall. Redirect it through drainage off-site.
- Always use a cloth “sock” over the perforated drainage line – the cloth sock over the full length of the perforated pipe stops vegetation and roots from entering and blocking your drainage system. It’s cheap insurance and can be bought from most hardware stores.
- Pre-plan any lighting or external power points within the wall – conduit needs to be run through the wall at the construction stage, not an afterthought once the wall is built.
- Weep holes within the wall – the main cause of retaining wall failure is from water pressure, weep holes allow excess water to escape from behind the wall.
Maintenance and Repair Tips for Retaining Walls in Gardens
Minor maintenance such as repainting and clearing weep holes and overgrown vegetation above the wall should be done as required.
Water pressure behind the wall
This is the most common problem with retaining walls and can be fixed by finding and redirecting the water source, installing drainage to the top of the wall to redirect it away as quickly as possible and making sure weep holes are not blocked.
Failed wall
Usually due to incorrect construction, lack of drainage or overloading. In some cases, the wall can be repaired, but in others, it will need to be completely rebuilt.
Settling or cracking
This is usually due to poor soil conditions or incorrect construction. In most cases, the wall can be repaired, but in some cases, it will need to be completely rebuilt.
Leaning wall
Usually due to inadequate drainage, poor soil conditions, incorrect construction or a surcharge on top of the wall such as structures, driveways or tree roots.
In some cases, the wall can be repaired, but in other cases, it will need to be completely rebuilt.
Conclusion
Retaining walls are a great way to add functionality and beauty to your property.
There are many different types of retaining walls in gardens available to you, so it is important to choose the right one for your needs.
Always check with your local council for requirements of building consents and if your not up to DIY get a qualified contractor to do the work for you.
Remember drainage is the main reason for retaining walls in gardens to fail so it is important to use adequate drainage.
Finally, remember to maintain your retaining wall regularly for longevity.
For more information on retaining walls in gardens go to our garden retaining wall page.
You will find information on suppliers and contractors in your area when you choose your area here.
