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3 Best Materials for Retaining Walls in Perth: A Short Guide for Discerning Homeowners

As experts in landscaping and landscape design based in Perth, Western Australia, we understand the significance of retaining walls in creating beautiful and functional outdoor spaces. We've got you covered! Let's explore the three best materials for retaining walls in Perth.

The Importance of Retaining Walls in Perth

Before we delve into the top materials, let's take a moment to understand what a retaining wall is, and why they are essential for many Perth properties.

Most sites are not naturally suitable for construction without some work, and we often need to raise or lower the soil (also known as cut and fill) to achieve the right level to construct a new home or landscape. This process of either raising or lowering the soil can leave differences in levels that would erode over time or outright collapse without something in place to prevent it. That's where retaining walls come in. Simply put retaining walls are structures designed to hold back the the soil and prevent erosion where differences in level occur. It's easy to overlook these seemingly innocuous structures, but they are often critical to achieving a design, especially when working with limited space.

When it comes to choosing the right material for your retaining walls, there are a lot of different options available and it can be hard to know what's best for your project. We've put together a list of the best options for Perth's unique location and terrain. Let's explore our picks for the top three retaining wall materials:

Stone Retaining wall
Image credit: Brickworks

1. Masonry Retaining Walls

Masonry walls are one of the best options for retaining walls in Perth. These walls are generally constructed using bricks, concrete blocks or natural stone over a concrete footing. When the difference in levels is greater than a certain height (you will need a structural engineer to design your retaining) the wall may also need concrete cavity fill. This involves two skins of masonry with a gap (or cavity) between that is then filled with concrete. Often there will also be steel reinforcing in this cavity with either steel rods, mesh or a combination of both. The reinforcing will be connected to the footing below through starter bars that have been preinstalled into the footing and extend up into the cavity. This firmly anchors the wall to the footing, creating a very strong and durable type of retaining wall that will last for many years.

Masonry walls are also a great use of space as they generally won't be wider than a few hundred millimeters. They can also have a variety of different finishes. A few of the more common finishes available are:

  • Face Brick: These are bricks that are designed to be aesthetically pleasing and for use as the final finish. Some examples include traditional or recycled recycled brick. These can be a great option because they are generally very low maintenance.

  • Rendered Brick: Rendered brick involves installing a sand cement render over the bricks and then either painting or texture coating the wall afterwards. This gives the wall a very smooth finish and has been a very popular option for many years. The render can be painted or texture coated in any Colour and looks very clean and modern. Microcement can also be applied for a premium finish!

  • Painted Brick: This option is becoming more popular again in recent years and involves simply painting the bricks in your desired colour. This keeps the shape and form of the bricks but just alters the finish to a uniform colour. For a more natural finish we recommend trying a mineral lime paint such as the paint made by Bauwerk Colour - it looks fantastic!

  • Stone Cladding: This involves cladding your retaining wall in natural stone and is typically completed by a Stonemason. Depending on the type of stone cladding you select this is perhaps the most premium of all the finishes and can look absolutely phenomenal.

The one major downside to this type of retaining wall is their high construction cost. Typically they are the most expensive type of retaining wall and so you may want to consider an option that comes with a lower price tag.

One final tip is to ensure your wall is adequately waterproofed. This may not be as detrimental for a face brick wall, but a rendered or painted wall will bubble.

2. Limestone Retaining Walls

Limestone retaining walls are perhaps the most common type of retaining wall in Perth and are an option you should seriously consider! Although quarried limestone blocks are available, most limestone retaining walls in Perth are constructed from man-made reconstituted limestone blocks, which are stronger and cheaper than their natural stone counterparts.

These walls are incredibly strong and versatile to build with for a variety of reasons. One key factor is that the blocks are so heavy that they can act as their own "footing", removing the need to install a concrete footing and wait for it to cure prior to building the wall (in most situations). We have generally found them to be anywhere from 20-40% cheaper than a comparable masonry wall which can be a huge saving!

Depending on your taste and style of home these may be unsuitable due to their cream colour and rough appearance. They do not look as elegant or "finished" as many of the masonry wall options. Additionally, limestone retaining walls take up more space than other retaining options (on any substantial retaining wall the face block will be 350mm wide) and usually have additional, hidden backing blocks behind the face block on the high side of the wall. Although you don't see these blocks as they typically start around 350-700mm below the ground on the high side, they can be problematic if you have limited space during the install or want to install something like a pool installed relatively close to the wall

3. Panel and Post Retaining Walls

Panel and post retaining walls are another common option for retaining in Perth. These are constructed using vertical posts installed deep into the ground, with concrete panels that slot between them. They are typically built using prefabricated, steel reinforced concrete posts and panels. For very high walls there are also fully galvanized steel posts available.

They are great space savers at around only 130mm wide and are by far the cheapest option for retaining walls in Perth. They are also the easiest type of retaining wall for DIY and this makes them an attractive option for building your retaining wall on a budget.

They are however our least preferred option of the three because they are less durable than masonry or limestone and the panels can be prone to cracking over time. We would also consider them to be in general, less aesthetically pleasing than limestone or masonry retaining walls.

We have included them in our top three materials due to their good availability in Perth, ease of installation (especially for anyone looking to DIY) and their attractive price tag.

Honorable Mentions

Although this blog isn't intended as the fully comprehensive guide for all types of retaining walls in Perth, we can't resist mentioning a few other honourable mentions:

Timber Sleepers: Timber sleeper retaining walls blend a more natural aesthetic with functionality, making them a popular choice among nature-loving homeowners. Reclaimed railway sleepers are a great weathered looking option that can be installed both horizontally or vertically depending on your taste. Just make sure not to use them near your productive plants as they will have been treated with creosol. Another good option is green (untreated) Jarrah - just make sure to treat the parts in contact with the soil with a bitumen coating for longevity. Treated pine is also an option that can be painted, stained or treated in a large variety of different finishes.

Colorbond Plinths: This method is only applicable to those planning to install Colorbond boundary fences, but it comes in so handy its worth mentioning. Galvanised, powdercoated steel panels or plinths can be installed below your Colorbond fence as minor retaining. We generally recommend Aliwall Plinths as they are very durable and look nicer than the other corrugated options. The plinths are 150mm each and can bed stacked to retain up to a 600mm difference in levels between properties (we recommend 50mm galvanised posts be installed in addition to the Colorbond posts for anything over two plinths or 300mm). Best of all they don't take up any extra space than a regular Colorbond fence, making them a very simple, clean solution to retaining close to your boundary.

Natural Stone Boulders: Although not technically a retaining wall, by incorporating natural stone boulders into a sloped garden bed, you can achieve a beautiful natural finish. The right blend of stone boulders and gorgeous planting can look really amazing and can be much more cost effective than building a retaining wall. This is definitely one to consider if you've got a bit of space to spare and you want a more natural looking solution.

Corten Steel: Corten steel and other types of weathering steel can be used to create retaining walls. These metals develop a beautiful, earthy looking rust layer or patina on the outside, which acts to protect the strong core within the metal. This allows them to be used as retaining walls and planter boxes and they are a really popular choice for both modern and classical style gardens. There are some prefabricated systems available in Perth, or you can speak to a specialist landscaper who can fabricate them for you on site out of Corten steel plate. These Corten steel walls are only as strong as their supports - so it's critical that they have adequate bracing.

Final Considerations

Before construction of a retaining wall you should check if you require Development Approval and a Building Permit from your local Council. Additionally, you will need plans from a Structural Engineer to submit to the Council. All retaining walls are considered structures and should comply with the relevant provisions in the Building Code of Australia (BCA), regardless of whether your wall needs Council Approval or not.

At Valley Design Co., we understand that each garden is unique, and your preferences matter. Our team of design experts is ready to help you make the right decision. Whether you're aiming for a rustic retreat or a modern paradise, we'll guide you through the process, considering your taste, budget, and property's specific requirements.

Your garden deserves the best, and we're here to bring your vision to life. The three best materials for retaining walls in Perth - masonry, limestone, and panel and post - offer an array of choices to suit your needs. If you're ready to enhance your outdoor space, don't hesitate to get in touch with us. Together, we'll create your dream landscape!

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