Timber Retaining Walls
All the information on Timber Retaining Walls. What type of wall, can you build them yourself and how to find an Experienced Licensed Contractor.
Looking to Build Timber Retaining Walls?
Start at the beginning – does your property need timber retaining walls?
If you are able to batter the land back to a level of 45 degrees you can get away with not having a retaining wall.
However, as land sizes decrease, getting the most usage out of your property by adding a timber retaining wall is a logical choice to create extra level space at your residence or commercial property.
The Benefits of Timber Retaining Walls
Aesthetically pleasing, timber retaining walls are used extensively in landscaping in Australia’s backyards.
If you choose to have timber instead of concrete or stone, on your property they can be fairly easy to install and maintain. They are also
- Cost effective
- Versatile, can be used in different areas
- Allow water seepage naturally
- Ease of construction
- Quick construction
- Fences etc are easily attached to the wall
Some disadvantages
- Susceptible to rot
- Don’t last as long as some other materials
- Some timbers warp, cup and split
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Here are 4 Popular types of Timber Retaining Walls
- Treated rough sawn timber
- Treated dressed timber
- Round logs
- Timber sleeper retaining walls
Treated rough sawn timber
would be the cheapest option, so consider its placement and its prominence in the location.
If you opt to choose rough sawn sleepers as your timber sleeper retaining walls, be advised there is no grading or Australian standard required in landscaping.
This means the quality of rough sawn timber may vary among the different suppliers.
Although rough sawn timber will have the natural timber features including knots, gum veins and grain, if you’re timber selection is based more on appearance, you will most likely expect to pay more for timber with the least amount of these features.
Treated Dressed timber
describes timber that is machined on all sides to an exact specification enabling the timber to fit well, adapting to any environment.
Because of the extensive treatment process, it is also one of the most costly, however it does provide a premium finish as well as durability.
Treated dressed timber is dried after the treatment reducing shrinkage as well.
Round logs
are a traditional look and are used widely for retaining walls able to support a superior load to other timbers.
It can be a cost effective option when building large areas of timber retaining walls. Round logs can be used as posts, with sleepers built as the rails of the retaining wall.
Timber sleeper retaining walls are a dearer option especially if railway sleepers are used, as good ones are hard to come by, but also one of the most popular choices.
Timber sleeper retaining walls have a solid earthy look, blending well into the Australian landscape.
As a guide, for treated hardwood sleepers you can expect to pay anywhere between $300-$450 per square metre or $75 per sleeper.
The Best Timbers to use in Timber Retaining Walls
Naturally durable timbers suited to timber retaining walls include
- Ironbark
- grey gum
- tallowwood
- forest red gum
- Radiata Pine (cca treated to min H5)
When Timbers are preserved with treatment to H5 their longevity is increased 25 plus years.
Durable class 1 timber or timber treated to H5 is recommended. The treatment decreases the risk of rot, fungus and insect damage to the retaining wall.
Aside from which look you are aiming for, each of these timbers have a different life span so this should be one of the key factors in your design choice.
In fact, before you try and choose, remember that if you have enlisted the services of an engineer, they will draw up the design plans and advise on the best timber for you.
The Engineer will factor in the type of soil, what load the retainer wall is bearing, as part of a functional design.
Treated pine logs are a cheaper option but do not expect them to last as long as timber sleepers. Aesthetically they do not look as nice, really, they look cheap, so it depends where your retaining wall is situated.
Durable class 1 timber or timber treated to H5 is recommended. The treatment decreases the risk of rot, fungus and insect damage to the retaining wall.
Factoring in the Costs for your Timber Wall
The final cost of your timber retaining wall is dependent on a number of possible factors:
- Whether you need the services of an engineer
- How much excavation is involved
- The amount of drainage required
- Height of the retaining wall
- Type of timber used
- The type of soil bearing the foundations
- The height of the bank being retained
- Load bearing capacity required
It is important to note that Australian states have varying retaining wall height restrictions that need to have prior approval through your local council before any construction works commence.
At Retaining Walls HQ we can connect you with qualified Tradespeople and Engineers equipped with the knowledge, experience and tools to complete the job from plans through to final construction with the experts in their field.
Needing an obligation free quote from a certified tradesperson for your timber retaining walls in your area? Choose Your Area
For other types of retaining walls follow this quick link or go to our home page.
Usefull Timber Industry Links
TPAA – Timber Preservers Association of Australia. Any discepancy on which timber to use is here.
Standards Australia – Relevant Australian standards used to build timber retaining walls.
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Timber Retaining Wall FAQ
There are many factors that will change the cost of a wall which are discussed on this page but an average figure in 2020 is as follows
- Treated Pine retaining walls average between $240 – $360 per square metre of wall.
- Hardwood retaining walls average between $310 – $460 per square metre.
Each Council does have some varying conditions so you should check your local councils specifications. However most councils in Australia allow walls upto 1 metre in height and 1.5 metres from a building or another retaining wall to be built without consent.
Second hand railway sleepers are a popular choice as long as they are in good condition due to their longevity and rustic look.
Treated pine either rough sawn or which has been dressed (smooth) is a cheaper alternative.
Without local council consent the max height is 1 metre but this does vary with each council. With council consent and Engineering plans the maximum height is determined by the size of the logs available.
Timber retaining walls usually require roughly the same distance in the ground as retaining above ground. A 6 metre log will therefore allow approx a 3 metre wall. An engineer will determine the diameter of the log required.
Yes. Lack of drainage behind a retaining wall is one of the main reasons a wall fails.
Treated rough sawn pine is the cheapest type of timber, or in some areas half logs can be cost effective. Dressed timber adds another process therefore slightly more expensive.