Whether you need approval generally depends on how tall the wall is, whether there's any load on the ground behind it, and how close it sits to boundaries, buildings and other walls. A low wall around a garden bed might be exempt development. Run a driveway along the top of an identical wall and everything changes, since the weight of cars adds pressure that needs an engineered design.
In New South Wales, retaining walls fall under the planning system. Small, simple walls may be exempt development under the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008, the Codes SEPP. Walls that meet set standards may be approved as complying development with a certificate (CDC) from council or a registered certifier. Everything else generally needs a development application (DA) to Wollongong City Council, assessed against council's local environmental plan and development control plan, which includes geotechnical requirements for sloping and landslip-prone land. Structural work also has to meet the National Construction Code, and residential builders need the right NSW Fair Trading licence. The rules have conditions attached and are updated over time, so use this guide as a general starting point. For a firm answer on your own wall, speak to council or a registered certifier.
When approval is likely
If any of the following sounds like your wall, plan on talking to a certifier or council and an engineer, and you may well need a CDC or DA.
- It's taller than a low garden edge: exempt walls are generally limited to around 600 mm of cut or fill, and height is measured from the ground level, so your wall may count as taller than it looks.
- There's a load above it: for example a driveway, a house or garage, a pool, a carport, a shed or a raised fill pad.
- It's close to a boundary, a building or another retaining wall, or it forms part of a pool barrier.
- Your land has a planning or hazard issue, such as landslip or geotechnical mapping, flooding, heritage, a drainage easement, or the wall would change how stormwater runs onto your neighbour's block.
Several of these can apply at once, which is how a wall that seems clearly exempt ends up needing sign-off. Terraced walls catch a lot of people out on steep Illawarra blocks: a pair of low walls stepped close together can be treated as a single tall wall, even if neither is high on its own.
When it may be exempt
Exempt development is designed for small, simple walls.
- Low walls retaining only garden soil, within the Codes SEPP height limits, with no load in the area that bears on the wall.
- Set back from the boundary by the required distance, clear of buildings and other retaining walls, and not part of a pool barrier.
- On land without disqualifying constraints: exempt development generally isn't available on heritage items, and other mappings or easements can rule it out. The wall also must not redirect stormwater onto neighbouring land.
Exempt is not the same as anything goes. No inspector will be looking over the job, which makes sound construction and drainage all the more important.
Landslip areas and engineering
Wollongong is unusual because so many homes sit on the lower slopes of the Illawarra Escarpment. Parts of those foothills are mapped by council as landslip or geotechnical risk areas, and on that land cutting into the slope or building a wall can need a geotechnical report and an engineer's design before council or a certifier will approve it. Your property's planning certificate (the section 10.7 certificate you got when you bought) shows whether the block is affected. Even off the mapped areas, a wall over the exempt height, or any wall with a surcharge, should be engineered to AS 4678.
What is surcharge?
No word comes up in our conversations more, and it's typically what turns a simple wall into an engineered one.
In plain terms, it's any weight bearing on the retained ground apart from the soil. In Wollongong it's most often a driveway. Our blocks are often steep, and level changes are everywhere: a driveway cut into the hillside in Mount Pleasant or Keiraville, a carport pad built up on fill in Farmborough Heights, or a parking bay above a terraced garden in Thirroul or Austinmer. Cars and utes are heavy, they come and go every day, and their weight pushes down into the fill the wall is holding back. A surcharged wall will generally need an engineer to design it to AS 4678, and our retaining walls crew builds to that design.
A quick guide to common situations
Use this table as a first check, then confirm the specifics with Wollongong City Council or a registered certifier.
| Your situation | Will you probably need approval? |
|---|---|
| Higher than a low garden wall (generally over around 600 mm) | Probably a CDC or DA, with an engineer involved |
| Any height, with a driveway, structure or fill pad behind it | Probably a CDC or DA, with an engineer involved |
| Close to a boundary, building or another wall, or part of a pool barrier | Probably; check with council or a certifier |
| Land mapped for landslip, flooding, heritage or with an easement | Likely a DA, possibly with a geotechnical report; check with council |
| Part of a bigger job that already has a DA or CDC | May already be covered; check the approved plans |
| Low wall, garden soil only, no surcharge, set back from boundaries, no land constraints | May be exempt; check every Codes SEPP condition first |
What skipping approval can cost you
The consequences usually arrive years down the track, which is why skipping approval can seem tempting and why it's a bad idea. A building inspector or a buyer's conveyancer may flag the wall, council can issue orders, and regularising it afterwards can mean engineering reports, uncovering completed work or rebuilding it entirely. That's not something you want to deal with while you're trying to settle a sale, or after a wall has moved in heavy rain.
Get the drainage right, whatever the paperwork
Of everything here, this is the part to hold onto. Most retaining walls fail because of water, and an Illawarra East Coast Low, particularly on a sloping block with clay or shale behind the wall, will expose any shortcut. Stormwater also has to go somewhere lawful: into your property's stormwater system or a council-approved discharge point, not onto your neighbour's land.
How we build walls that last
Wet soil is far heavier than dry soil, and trapped water adds hydrostatic pressure the wall was never designed to carry. With nowhere to drain, that pressure builds until the wall leans, bulges or cracks, and a few days of heavy coastal rain can soak a hillside right through. Clean drainage gravel behind the wall, wrapped in geotextile, with an ag line at the footing and weep holes through the face, relieves that pressure for a tiny fraction of what a rebuild costs. We put them into every wall we build, whether it's inspected or not, and we work with your engineer, certifier and council when approval is needed. Our excavation crew also puts in a Before You Dig Australia enquiry before a single bucket goes into the ground, so services are located first.