What this guide covers
Contact Retaining Walls Canberra about retaining walls in Canberra.
Treated pine or hardwood
Yakka Labour gives $250 to $450 per square metre of face for treated pine on timber posts, with a life of 15 to 25 years, and $350 to $550 for hardwood sleepers, with 20 to 30 years. It says treated pine is the cheapest and easiest to build, but it is timber in contact with wet soil, so it will not last forever. It suggests it for low garden beds and terraces, and not for boundary walls you want to forget about.
Treatment and moisture
Yakka Labour says a well-built treated pine wall uses H4 or higher treated timber with good drainage, and that poor drainage, wet clay soils and low-grade timber shorten its life. Karven makes the same point from the other side and says skipping drainage is the most common reason cheap walls fail. Ask each builder which treatment class they allow for and what sits behind the sleepers to let water out.
A short wall is not an exempt wall
ACT Planning says a retaining wall does not need a building approval if it is not higher than 1.2 metres from the top of the wall to the lowest adjacent ground. Its development approval page uses lower limits, 0.4 metres above datum ground level, for any part of a wall within 1.5 metres of a side or rear boundary. A low timber wall near a fence can therefore sit under a rule you did not expect. Read both pages for your block.
Do it yourself or hire
Yakka Labour says a low treated pine sleeper garden wall, up to a few courses high, is a reasonable do-it-yourself job, with materials at roughly $100 to $180 per square metre. It says anything over about 600 millimetres, on a boundary, near a building or supporting a load is a different matter, and that the hard parts are post holes, getting posts plumb and doing the drainage properly. Ask a builder what they would do differently.
Canberra weather
The Bureau of Meteorology's Canberra Airport statistics show annual rainfall of 636.7 millimetres, with 69.6 rain days a year, and a lowest recorded temperature of minus 8.7. Timber in damp ground will cycle through wet and cold repeatedly. Ask a builder how they protect the cut ends of posts and sleepers and what they set the post bottoms in.
Questions to ask each business
- Which timber and which treatment class is allowed for?
- What post depth and spacing is quoted?
- How will water drain from behind the wall?
- Does the quote include removing the old wall, if there is one?
- Who requests Before You Dig plans?
- Who is responsible if approval is needed?
Before you accept
Compare at least two written quotes for the same height, length and timber. Ask how long they expect the wall to last in your soil and what is in writing, and keep the contract and photos.
How long does a treated pine retaining wall last?
Yakka Labour says 15 to 25 years for a well-built wall with H4 or higher timber and good drainage. Poor drainage shortens it.
How much does a timber retaining wall cost?
Yakka Labour gives $250 to $450 per square metre for treated pine and Karven gives $250 to $450 for treated timber. Both are national guides, not Canberra quotes.
Does a low timber wall need approval?
ACT Planning gives limits for building and development approval, with lower limits near boundaries. Check both pages or ask a certifier.
Can I replace an old timber wall?
Yakka Labour gives $50 to $150 per square metre of face for removing an old wall. Ask each builder to list removal and soil handling.
Sources
- Access Canberra: choosing a tradesperson (read 31 October 2026)
- ACT Planning: construction licences (read 31 October 2026)
- ACT Planning: check if you need a BA (read 31 October 2026)
- ACT Planning: check if you need a DA (read 31 October 2026)
- Before You Dig Australia (read 31 October 2026)
- Yakka Labour: retaining wall cost per m2 in Australia, 2026 guide (read 31 October 2026)
- Karven: retaining wall cost in Australia, 2026 price guide (read 31 October 2026)
- Bureau of Meteorology: Canberra Airport climate statistics