Classic
Smooth Grey
Plain natural-grey concrete with a smooth face – the quiet standard wall.
Smooth / plain · Even, lightly formed concrete
See this design → Retaining walls · under fences · gardens
Concrete sleeper retaining walls Sydney
Concrete sleepers hold soil. A fence gives you a boundary. We build both – a standalone garden wall, or a wall sitting directly under a new Colorbond or timber fence – and we quote the site, not a catalogue.
A concrete sleeper is a steel-reinforced concrete board. It stacks between galvanised steel posts to make a wall. That wall can stand on its own in a garden, or it can sit on the boundary under a new fence where your yard and the neighbour’s are at different levels.
Sydney blocks are often cut on one side and filled on the other. Without a wall, soil on the high side pushes the fence, escapes under it, and leaves a gap. A sleeper wall on the line keeps the soil where it belongs and gives the fence a finished ground level to sit on.
The face you choose – smooth grey, charcoal, timber-look, rock, sandstone, stacked stone, block or flagstone – is the look. The posts, the drainage, the footing and (where the site needs it) an engineer are what make the wall work. We do not invent a maximum height from a product photo.
This page covers standalone walls, walls under fences, how a fence and a wall differ, the eight distinct faces we quote, and the site questions that change the job. For low timber sleeper walls built only as part of a fence, see retaining walls under fences.
Fence or retaining wall? They do different jobs
A fence separates two yards. It gives privacy, a boundary and somewhere to hang a gate. It is not automatically a retaining structure. Soil piled against a Colorbond sheet or a paling fence will push it, rot timber, and eventually lean the line.
A retaining wall holds soil. Its posts, sleepers and drainage are sized for that load. When a fence sits on top of a wall, the combined arrangement still has to be thought through: finished ground level, fence height, whether the fence posts and the wall posts are the same members or separate, and where water goes.
If someone has been using an old fence as a wall, we say so. Replacing only the fence and leaving the soil against it repeats the same failure.
Standalone concrete sleeper retaining walls
A standalone wall does not carry a fence. Typical jobs are garden level changes, a driveway dropping to a lower lawn, a usable terrace on a sloping block, or replacing a timber sleeper wall that has reached the end of its life.
What we look at on site:
- How much level change you actually have – not a guess from the street
- Ground conditions and access for posts and a two-person lift
- What sits above the wall: lawn, path, driveway, a building, a pool
- Surface water and where it currently runs
- Existing structures and the neighbour’s side
- Post spacing that matches the sleeper length you choose
- Foundations / post holes suited to the site – there is no single hole spec for every block
- Backfill that drains instead of holding water
- Whether the height, soil or surcharge means an engineer or council advice
We do not publish a “safe height” for a DIY wall. If the site is more than a simple garden step, we say what extra advice you need before we build.
Concrete sleeper retaining walls under fences
This is the job we quote most often with a new fence: the two yards are not at the same level, and the fence needs a wall under it.
Your yard (high side)
Ground level
Fence
Concrete sleeper wall
Neighbour (low side)
Same fence, seen from below
Wall face
Ground level
The wall sits on the boundary line. The fence sits at the new finished level on top. From the high side you see a normal fence. From the low side you see sleeper face, then fence.
That arrangement changes fence height: the fence is measured from the finished ground on each side the way the job and any pool-barrier rules require – not “whatever is left after we bury a panel”. Tell us if the fence is part of a pool barrier.
Fence posts and retaining posts can be the same steel in a simple low wall, or separate members when the wall and the fence need to work independently. We decide that on site. Drainage and runoff still have to leave the high side without soaking the neighbour’s yard as a sheet of mud.
Typical sequence: measure both sides → agree the finished levels → remove the old fence (and the old wall if it has failed) → set wall posts → stack sleepers → set or continue fence posts → hang the fence and gates. A new wall under an old fence is only possible when the existing posts and line can take it. Often they cannot.
Choose the look
Concrete sleeper designs
These are distinct faces, not a copy of any one supplier’s catalogue. If several makers sell the same smooth grey board under different names, it appears here once.
Eight distinct faces – not a supplier catalogue. Tap a design for sizes, uses and how it sits under a fence.
Classic
Smooth Charcoal
The same clean smooth face in a dark charcoal that sits with Monument and Night Sky fences.
Smooth / pigmented · Even, lightly formed concrete
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Textured
Timber Woodgrain
A moulded timber-grain face in concrete – the look of sleepers without the rot.
Moulded woodgrain · Linear timber grain
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Decorative
Rock Face
A split-stone face in charcoal concrete for walls that should look like masonry.
Rock / split-stone · Irregular stone face
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Stone
Sandstone Cove
A warm sandstone-coloured face with a soft scooped stone texture.
Sandstone cove · Soft scooped stone
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Stone
Stacked Stone
Several ledgestone courses moulded into one sleeper – a dry-stone look without laying stone.
Stacked / ledgestone · Horizontal stone courses
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Decorative
Block Pattern
A regular ashlar block grid in charcoal – ordered, modern masonry.
Ashlar block · Regular block joints
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Stone
Flagstone
An irregular flagstone face in mixed bone and latte tones.
Flagstone / crazy paving · Irregular stone paving
See this design →Typical specifications
The numbers below are the ranges we see across Australian concrete sleeper systems. They are not a design for your block. The manufacturer you end up with, and the engineer if you need one, set the actual board and post.
- Course heightCommonly 200 mm per sleeper – five courses make about one metre of wall face
- LengthTypically 1.6 m, 1.8 m, 2.0 m or 2.4 m between post centres – the board itself is a little shorter so it seats in the post channel
- ThicknessCommonly 75–80 mm on residential walls; thicker boards are used where the design needs them
- MaterialSteel-reinforced concrete. Compressive grade varies by manufacturer (often in the 40–65 MPa range)
- PostsHot-dip galvanised steel – C-channel (PFC) or H-beam (UC), plus corner and end posts
- HandlingHeavy. A two-person or mechanical lift on every board
- Wall heightSet by the site, soil, surcharge and any engineering – not by the sleeper face design
How the wall is built
Site preparation
We look at the existing ground, what has to be excavated, where the finished levels should land, how we get materials in, what is already there (fences, paths, services) and whether underground services need locating. We do not dig blind on a guess.
Foundations and posts
Posts carry the load. Hole size and depth depend on height, soil and the post specified for the wall – there is no universal hole that suits every Sydney clay and every sand. End, corner and intermediate posts are different members. Coastal or aggressive sites may need a coating conversation with the steel supplier.
Sleepers
Boards slide into the post channels and stack. Each course adds about 200 mm of face. Alignment matters: a wander in the first course shows on the last. We do not mix random leftover lengths to “make it work” on a visible face.
Drainage and backfill
Water that cannot leave becomes pressure. We plan drainage material, outlets and the path for surface water with the wall. Backfill is not “whatever came out of the hole” if that material holds water. We will not write a recipe that pretends every soil is the same.
Soil and surcharge
Clay that moves, a driveway above the wall, a pool, a shed slab, an existing wall uphill – any of these can change what the wall needs. That is when we talk about an engineer instead of treating it as a three-sleeper garden step.
The fence
If a fence is part of the job we set it out with the wall: Colorbond, timber, or security where the site is commercial. Unsupported combinations – for example treating a slat screen as a retaining wall – are not something we will build.
When does a retaining wall need engineering or approval?
Requirements can vary depending on the site and local regulations. Height, whether the wall is on a boundary, soil, what sits above it, drainage, and the council’s development rules all matter. Some low garden and under-fence walls proceed as part of the fence job. Others need an engineer’s drawing, council advice, or both.
Fencing Sydney does not certify engineering designs and does not approve work for council. If your site needs that step, we say so on the measure and we work to the documents you obtain. We would rather pause than build a wall that is the wrong structure for the load.
Common questions
What is a concrete sleeper retaining wall?
Steel-reinforced concrete boards stacked horizontally between galvanised steel posts to hold back soil. They can stand on their own in a garden, or sit directly under a new fence where the two yards are at different levels.
How long do concrete sleepers last?
Makers commonly talk about a multi-decade design life. How long your wall lasts depends on the posts, the drainage, the soil and how it was installed – not just the board.
Are concrete sleepers better than timber?
They will not rot, warp or attract termites, and they do not need oiling. They are heavier and a two-person lift. Timber sleepers still have a place on low under-fence walls – see our treated pine sleeper walls.
Can a concrete sleeper retaining wall support a fence?
A wall and a fence can be built as one job, but they do different work. The wall holds soil. The fence is for privacy and boundary. Posts, finished ground level and drainage have to be planned together. The fence is not automatically a retaining structure.
Can you install a fence directly above a retaining wall?
Yes, that is a common Sydney job: wall first (or wall and fence posts in one sequence), then the fence sitting at the new finished level. See walls under fences.
Can you build a retaining wall underneath an existing fence?
Sometimes. Often the old fence has to come out so posts can be set properly. We will say so on the site visit rather than force a wall under a fence that is already leaning.
Can you replace timber sleepers with concrete sleepers?
Yes, when the posts and drainage can be brought up to what the new wall needs. Swapping boards into rotten timber posts is not a proper replacement.
What concrete sleeper designs are available?
Eight distinct faces: Smooth Grey, Smooth Charcoal, Timber Woodgrain, Rock Face, Sandstone Cove, Stacked Stone, Block Pattern and Flagstone. See designs.
Can concrete sleepers be coloured?
Yes – charcoal, sandstone and timber-look faces are pigmented through the mix. Exact colour varies by manufacturer and batch. We bring samples to the measure.
How high can a concrete sleeper retaining wall be?
Height is a site question – soil, slope, surcharge (driveways, buildings, pools) and council rules – not a number we invent from a sleeper catalogue. Low garden and under-fence walls are common. Taller or loaded walls may need an engineer and approval.
Do concrete sleeper walls need drainage?
Yes. Water behind a wall is extra load. Drainage material, outlets and surface-water paths are part of a proper wall.
Does a retaining wall need engineering?
It can. Requirements vary with height, location, soil, loads above the wall and the local council. We tell you when the site is outside a simple under-fence wall.
Does a retaining wall need council approval?
Sometimes. It depends on height, boundary, the council and whether the wall is part of other work. We do not approve designs for council. Where approval or an engineer is needed, we say so before you commit.
Can a retaining wall be built on a boundary?
Often that is exactly where the level change is. A retaining wall is not covered by the Dividing Fences Act in the same way as a fence. Who pays is usually about who created the level difference, or what the neighbours agree.
Can retaining walls be installed on sloping blocks?
Yes. Sleepers can step with the fall. Posts still need proper holes and the drainage still has to work at each step.
Can the fence and retaining wall be installed together?
Yes – that is how we prefer to build an under-fence wall. One measure, one sequence, one quote with the wall as its own line.
What happens if the ground level differs between properties?
The high side needs something to hold the soil or it will push on the fence and spill under it. That is the usual reason we quote a sleeper wall under a new Colorbond or timber fence.
Can concrete sleepers be used for garden retaining walls?
Yes. Standalone garden walls use the same designs, without a fence on top.
Can they be used beneath Colorbond fencing?
Yes. Smooth Charcoal and Block Pattern sit particularly well with Monument and Night Sky. Any face can go under Colorbond if you like the look.
Can they be used beneath timber fencing?
Yes. Remember timber gates are lapped only. The wall and the fence are still two jobs sharing a line.
What happens if there is an existing retaining wall?
We look at whether it can stay, needs repair, or should come out with the old fence. Building a new fence on a failed wall is a short-term fix.
How do I choose a sleeper design?
Start with how visible the wall is. Hidden side boundaries are usually Smooth Grey or Smooth Charcoal. Street fronts and gardens use woodgrain or a stone face. Use the chooser then we confirm samples on site.
How do I get a quote?
Use the form on this page or call 0421 233 434. We need the suburb, the length, the level change, and whether a fence sits on top. The owner measures on site.
Enquire about a concrete sleeper retaining wall
Suburb, length, the level change, and whether a fence sits on top. We reply with a site visit.
- 1 What you need
- 2 Details
- 3 Photos
- 4 Contact
- 5 Review
Concrete sleeper walls, quoted on your block
Choose a face on this page, then book a free measure. We will tell you if the wall is a simple under-fence job or needs more advice.