Sloping blocks
Retaining wall engineering in Canberra
In the ACT, a retaining wall up to 1.2 m high needs no building approval. Above that, design and construction standards apply, and the height that counts is the earth cut the wall holds back. We design walls your builder can price and your certifier can approve.
- From $890 + GST ($979 inc GST), fixed before we start
- Fixed quote in under 20 minutes on average, during business hours
- 1.2 m the building approval line, measured to the lowest ground next to the wall
Prefer to talk? Call 02 6189 9876
Or email info@canberrastructuralengineers.com.au
Monday to Friday, 8:00am to 5:00pm
- Engineering onlyWe never sell the repair or the build.
- Walls from $890 + GST($979 inc GST), confirmed before we start.
- Fixed quote in under 20 minutes on averageDuring business hours, Monday to Friday.
- Canberra and the Queanbeyan sideEvery district, plus Queanbeyan, Jerrabomberra and Googong.
In short
Retaining wall engineering in Canberra starts from $890 + GST ($979 inc GST). No building approval is needed for a wall up to 1.2 m high, measured from its top to the lowest ground next to it; above that, design and construction standards apply. Access Canberra says the height is the actual earth cut retained, and our drawings show it. Same prices across Canberra, Queanbeyan, Jerrabomberra and Googong.
- Fee
- From $890 + GST ($979 inc GST)
- Quote
- Fixed, in under 20 minutes on average, during business hours
- You receive
- Calculations and drawings for your certifier and builder
- Building approval line
- 1.2 m, from the top of the wall to the lowest adjacent ground
- Near a boundary
- Planning limit of 0.4 m in the front zone or within 1.5 m of a side or rear boundary
- Area
- Every Canberra district, plus Queanbeyan, Jerrabomberra and Googong
Do I need approval for a retaining wall in the ACT?
Not building approval for a wall up to 1.2 m high, measured from its top to the lowest ground next to it. Between 1.2 m and 1.5 m it is only partly exempt and must meet the code, and taller walls need building approval. Planning limits are lower near boundaries.
The building approval exemption is in the Building (General) Regulation. A wall up to 1.2 m, measured "from any point at top of retaining wall to lowest adjacent ground level", needs no building approval (BA). Up to 1.5 m it is only partly exempt: it must comply with the exempt building code, or the building code's deemed-to-satisfy provisions. Over 1.2 m, ACT Planning says "design and construction standards will apply".
Development approval has its own, lower limits. Between the front boundary and the building line, or within 1.5 m of a side or rear boundary, an exempt retaining wall can be no more than 0.4 m above datum ground level. The full set of limits, including cut and fill elsewhere on the block, is in our guide to retaining wall rules in the ACT.
How is retaining wall height measured in the ACT?
By the earth the wall holds back. Access Canberra says the height means the actual earth cut being retained, and engineer plans must show it.
Access Canberra's Construction Note 005/2021 puts it plainly: "all engineer plans must clearly show the actual height dimension of the earth cut to be retained".
So our drawings dimension the earth cut the wall retains. That number can differ from the overall height of the blocks or sleepers, and it's the one your certifier looks for when deciding which rules apply.
The rest of the drawings follow the Registrar's form AF2025-18, which lists retaining wall details among the documents a certifier lodges for a house: drainage, founding levels and backfill.
| On our drawings | What it shows |
|---|---|
| Earth-cut height | The depth of soil the wall retains, dimensioned |
| Footing and founding level | How deep the wall's footing goes, and what it sits on |
| Drainage | The drain behind the wall and where the water goes |
| Backfill | What goes behind the wall and how it's placed |
| Wall details | Post, sleeper, block or stone sizes, and any reinforcement |
| Loads above | A fence, driveway, carport, pool or house footing near the top |
Which retaining walls do you design?
Walls in the material you want. For each one we design the wall, its footing, the drainage behind it, the founding level and the backfill.
Sandstone block walls
Cut sandstone blocks stacked as a gravity wall, sized for the height and the slope behind it.
Concrete sleeper walls
Sleepers between steel posts set in concrete footings. We size the posts, their spacing and the footings.
Masonry block walls
Reinforced, core-filled block walls on a concrete footing, for taller or loaded walls.
Concrete walls
Reinforced concrete where the height, the load or the space behind the wall calls for it.
Planning a fence on top?
The building approval exemption for fences doesn't cover a fence that is part of a retaining wall. Tell us early, and we design the wall to carry the fence posts; your certifier confirms which approval applies. Walls beside a pool are common on sloping blocks too: see pool engineering.
Why do retaining walls get big on Canberra's newer estates?
Because several newer estates sit on hilly ground. Cut-and-fill blocks often need walls on more than one side, and those walls retain more earth.
Builders describe estates such as Jacka, Whitlam, Denman Prospect and Googong as hilly, undulating or mountainous. On blocks like these, a level platform for the house means cutting into the slope, filling it, or both, with a wall at each change in level.
A wall on a new-estate block may sit on, or hold back, fill placed when the estate was built, so we check the founding level and the ground under the wall before the design is final. Canberra's rock is often deeply and unevenly weathered, so one end of a long wall can find rock while the other stays in clay. Our guide to building on a new estate block covers fill and slope in more detail.
We design walls across the hillside suburbs of the Molonglo Valley and over the border in Googong, where NSW rules apply to approvals.
What's included in retaining wall engineering?
Engineering calculations and drawings your certifier and builder can use, from $890 + GST ($979 inc GST). Your fixed quote says if a site visit is needed.
✅ What we do
- Design the wall, its footing and the founding level
- Detail the drainage and backfill behind it
- Dimension the earth-cut height on the drawings
- Allow for a fence, driveway, pool or house footing above the wall
- Design the footings under the wall to suit the site classification where one is needed
❌ What we don't do
- Build the wall, or recommend who should
- Approve it: that's your certifier
- Survey the boundary or set out levels
- Assess trees near the wall (an arborist does that)
The price rises with the wall's height and length, the slope behind it, the ground it sits on and what it carries. Every published price is on our prices page.
What should I send for a retaining wall quote?
We're engineers only. We don't build walls or sell blocks and sleepers, so the design is sized for your slope, not for a product.
- Photos of the slope, from the side if you can, with something for scale
- The height of earth you need to hold back, and the wall's rough length
- The material you'd like: sandstone, sleepers, block or concrete
- Anything near the top: a fence, driveway, pool or the house
What happens next?
Three steps, and you know the price before anything is booked.
Send photos or plans
Use the form above, or our full quote form. Add up to 5 photos or plans.
Get a fixed quote
In under 20 minutes on average, during business hours. It says what we'll design and if a site visit is needed.
Design and drawings
We send calculations and drawings, with the earth-cut height shown, for your certifier and builder.
Often needed alongside a retaining wall
Every service is quoted at a fixed price before we start. Send photos or plans and we reply in under 20 minutes on average, during business hours.
When does a retaining wall need approval in the ACT?
Two separate tests apply: building approval from 1.2 m, and a planning limit as low as 0.4 m near boundaries. How height is measured, fences on walls, and who pays between neighbours.
Read the guide
Footings, slabs & site classification
Site classification and footing or slab design for new homes, rebuilds, granny flats and extensions, with the soil test at cost.
$1,290 + GST($1,419 inc GST) See the service
Pool engineering
Pool shell, retaining and footing engineering for pools on slopes, near boundaries and close to the house.
$990 + GST($1,089 inc GST) See the serviceRetaining wall questions
Something else on your mind? Call 02 6189 9876, email info@canberrastructuralengineers.com.au or send photos for a fixed quote.
How much does a retaining wall engineer cost in Canberra?
From $890 + GST ($979 inc GST) for a typical house wall, fixed before we start. Taller or longer walls, steep slopes, poor ground or loads above the wall can raise it.
Do sleeper walls under 1.2 m need an engineer?
Not for building approval. A wall up to 1.2 m needs no building approval, but planning limits can be lower near boundaries. A low wall carrying a driveway, a fence or a house footing above it is still a design question.
Can I put a fence on top of my retaining wall?
Yes, if the wall is designed for it. The building approval exemption for fences doesn't cover a fence that is part of a retaining wall, so tell us early and ask your certifier which approval applies.
Who pays for a retaining wall on the boundary?
That's between you and your neighbour. The Common Boundaries Act 1981 covers dividing fences and party walls, and doesn't mention retaining walls. We design the wall either way.
Do you design retaining walls in Queanbeyan and Googong?
Yes, at the same prices. They're in New South Wales, so NSW rules apply to approvals there, not the ACT limits on this page.