Creating usable flat areas and holding back earth that would otherwise give way, are just some of the primary functions of retaining walls. So how do you know if the construction of a block, timber, concrete or rock-filled retaining wall is the best solution for your landscape?

Retaining walls provide so much more than just functionality. With the right materials, technique and workmanship, they can become a unique and beautiful structure in an otherwise uninspiring garden.

To help determine what retaining wall material is best for your landscape, we’ve put together a detailed list of the characteristics and key advantages and disadvantages. Retaining walls 101…

Concrete Block Retaining Walls

rendered block retaining wall 101

Photo Credit: Concrete Block Rendered Retaining Wall, Houzz

Strength, versatility and aesthetics are some of the key features that come to mind when considering a block retaining wall. Although concrete blocks are typically considered a sterile or ‘harsh’ material, a variety of aesthetic finishes can be applied to create a softer, more modern appearance. Available in a number of different brands, locking wall systems and finishes – block retaining walls are fast becoming the go-to choice for many residential and commercial landscapes. Block retaining walls can often be referred to as ‘Besser’ blocks, ‘Versaloc’ blocks, ‘Tasman’ blocks, split face blocks, grey blocks or concrete masonry units.

Advantages

  • Structurally sound
  • Suitable for large scale projects and high walls
  • Versatile – can be used in a variety of applications big or small
  • Different aesthetic finishes can be applied – rendered, stone clad, painted, bagged
  • Durable, hard wearing and not prone to rotting
  • Longevity
  • Available in a range of colours
  • Caps to provide a complete finish to the top of the block wall

Disadvantages

  • Costly due to other materials required for installation – steel, concrete footings, additional cost to create different finishes
  • Labour intensive
  • Can look sterile or harsh look in their raw state

Building a timber retaining wall comes with many benefits such as it’s natural charm, quick installation and ability to effortlessly enhance any outdoor garden environment. However, understanding the pros and cons of installing a timber retaining wall will help you to make an informed decision as to whether timber is the right solution for your landscape project.

Advantages

  • Cost effective
  • Fast to install
  • Soft, natural aesthetic
  • Can be made from recycled ‘eco friendly’ materials
  • Minimal footings
  • Quick wall solution

Disadvantages

  • Shorter lifespan
  • Can be vulnerable to rotting and termites
  • Not suitable for complex projects or large scale retaining walls
  • Not flexible

Made out of precast concrete and reinforced steel, concrete sleeper retaining walls are heavy duty and often used in industrial landscapes or garden areas that have a ‘lower profile’. The strength of a concrete sleeper retaining wall allows you to build at height and is often considered as a cheaper alternative for large scale projects.

Advantages

  • Extremely durable and structurally sound
  • Cost effective for large scale wall
  • Minimal footings and excavation
  • Concrete reinforced and suitable for heavy duty applications
  • Low maintenance
  • Never rot, warp or be affected by pests
  • Timber look and coloured concrete sleepers are available

Disadvantages

  • Not aesthetically pleasing – more of a ‘sterile’ look
  • Heavy lifting and machinery required for installation with a typical sleeper weighing 25kg plus
  • Visible steel posts
  • Tops of walls are left exposed with no caps to create a neat finish
  • Not ideal for high-profile garden areas

Sandstone Log Retaining Walls

Sandstone log retaining wall garden landscaping

Photo Credit: Sandstone Log Retaining Wall, Brisbane Sandstone

If you’re looking for a natural and decorative extension to your home, then a Sandstone ‘log’ or ‘block’ retaining wall is the perfect solution. Reasonably cost effective and easy to install, each piece of sandstone is unique in size, texture and colour. Easy to maintain with regular pressure cleaning, a sandstone retaining wall application is a timeless option that is sure to beautify any outdoor landscape.

Advantages

  • Durable
  • Unique, natural aesthetic
  • Easy to maintain and clean
  • Reasonaly cost effective
  • Minimal footings
  • Best suited for square set and low-level walls

Disadvantages

  • Mass volume stone – high delivery / transport costs
  • Not suitable for intricate corners or small spaces
  • Sandstone can be hard to source
  • Inconsistent and minimal colour choices
  • Can be challenging with access and require big machinery

Constructed with wet or dry stones, a stone retaining wall is basically an organised collection of specially shaped rocks which cleverly interlock together to form a structure. Typically used for feature walls and high end aesthetics, a stone retaining wall will be sure to create a ‘wow’ impact in a high-profile garden area. A skilled landscaper or stone mansion is required to ensure structural integrity and the application of individual stones can be somewhat time consuming.

Advantages

  • High end aesthetic
  • Wow or statement wall feature
  • Suitable for small garden spaces
  • Variety of stones, shapes and textures
  • Natural / mosaic appearance

Disadvantages

  • Not suitable for large scale structural walls
  • Labour intensive
  • High cost
  • Skilled tradesman required

Did you know that gabions were originally used as protection for infantry and artillery in the military? Gabion, meaning ‘big cage’ in Italian, is essentially a system of wire mesh stacked cages, usually hand assembled and filled with rocks. The base is generally constructed with level reinforced concrete footings upon which the barrier is built, as part of a structurally sound retaining wall. Labour intensive and ‘raw’, gabion retaining walls have a unique aesthetic and have become more popular in recent times.

Advantages

  • Durable and long-lasting
  • Less impact on the environment than other construction materials with use of concrete and recycled aggregate
  • Suitable for large scale walls
  • Aesthetically pleasing and unique wall structure
  • Flexible – ideal for uneven or curved retaining wall solutions

Disadvantages

  • Very labour intensive
  • Can become costly
  • Raw look, mesh wire finish

Do I need council approval?

Our general rule of thumb is to seek professional advice and always check with your local councils development regulations. You can read more information about development approvals on our earlier blog here.

Will I require engineered drawings?

In many cases, retaining walls over 1 metre in height will require engineered drawings or plans. These drawings are crucial in dictating how a retaining wall is to be built in order for it to be safe and structurally sound. This is something that your local council can advise you on.

In cases where council approval and engineered drawings are required, a certifier will need to be nominated. The certifier is to sign off on critical stage inspections points of the construction and ensure all works have been completed according to the engineered drawings and development consent.

So which style of retaining wall do you think is going to best suit your project? Whether installing a retaining wall on a new property or updating the structural integrity of an existing wall, there is plenty of information to consider.