A retaining wall can turn a sloping block into level garden beds, a flat lawn or a usable courtyard. It also holds back a surprising weight of soil and water. That is why walls need more planning than most garden projects. A wall that looks fine on day one can lean or crack within a few years if the basics are skipped.
This guide covers the questions to answer before any digging starts. It looks at approvals, drainage, neighbours and materials. The rules quoted here come from council and state planning guidance. Rules differ between states and councils, so treat this as a starting point and check with your own council.
Start with the purpose of the wall
Think about what the wall needs to do before you choose a material. A low edge for a raised garden bed is a very different job from holding up a driveway. The City of Albany describes a retaining wall as a structure that supports soil where ground levels have been raised by filling or lowered by cutting. It also warns that a fence should not retain soil unless it was built for that purpose.
The finished look matters too. A wall can frame a lawn, create steps between levels or form seating at the edge of a patio. If you are still settling on a look for the whole yard, our guide to choosing the right landscape design style for your Perth home can help. The wall should suit the house and the planting, not fight with them.
Do you need approval for a retaining wall?
Height is the first test in most places. In Western Australia, council guidance commonly sets the line at 500mm. The City of Albany says any retaining wall over 500mm high needs a building permit before construction. The City of Wanneroo applies the same 500mm trigger and counts the total height of tiered walls.
A lower wall is not always free of paperwork. Albany notes that a permit may still be needed if a wall under 500mm encroaches over the boundary or weakens a nearby building. The same applies if it reduces the bearing capacity of the neighbouring land. Changing the natural drainage of the site in a harmful way can also trigger a permit.
New South Wales works differently. Some retaining walls count as exempt development under the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008. As City of Newcastle guidance on retaining walls explains, a wall that goes beyond any listed standard needs consent first. Depending on the design, that could mean a complying development certificate or a development application.
The current exempt standards for earthworks and retaining walls set several height and distance limits. Cut or fill must not go more than 600mm below or above existing ground level. The wall itself must be no more than 600mm high. It must sit at least 1m from each lot boundary and any registered easement, sewer main or water main. Rules are reviewed from time to time, so check the current policy and your local council before you build.
Engineering and loads
A wall holds back more than soil. The City of Wanneroo lists buildings, swimming pools, footings, vehicles and wind on dividing fences as possible extra loads. It also points out that some ready made wall systems are rated for soil only. A product that suits a garden bed may not be right below a driveway or a pool.
For walls that need a permit, councils in WA expect engineering input. Albany asks for construction details certified by a practising structural engineer. It also asks for a site plan showing existing and proposed ground levels. If a wall will carry a fence or sit near a building, get that advice early rather than after the blocks arrive.
Plan the drainage from the start
Water is the quiet enemy of most retaining walls. Rain soaks into the soil behind the wall and adds to the weight it must hold. Albany asks for a subsoil drainage detail with every retaining wall application. That tells you how seriously councils take this part of the job.
NSW exempt development rules say retaining walls must have adequate drainage lines connected to the site’s stormwater system. The works must not redirect the flow of surface water or ground water. They must not cause sediment to wash onto a neighbouring property. Think about where water will go once it reaches the base of the wall. A wall that sends runoff into the yard next door can cause problems that cost far more than the wall.
Talk to your neighbours early
Boundary walls are where many disputes begin. Wanneroo explains that each landowner must retain the soil that results from earthworks on their own property. Where both neighbours have changed their levels, they should agree on how to share the cost. The City says these disputes are a civil matter and it does not step in.
WA rules also cover work that affects the land next door. Under the Building Act 2011, the adjoining owner’s consent is needed where works will affect their land. Albany says walls, footings and subsoil drainage should generally sit wholly within your own lot. A friendly conversation before the plans are drawn is much easier than one after the excavator arrives.
Choosing materials
Common choices include timber sleepers, concrete sleepers with steel posts, masonry blocks, limestone and natural stone. Each one has a different look, lifespan and price. Local rules can rule some out. The City of Albany says timber materials are not permitted on a property boundary.
Match the material to the height, the load and the style of the garden. Interlocking blocks can create gentle curves, while sleepers suit straight runs. Stone softens a garden and blends with planting. The classic landscape design principles of balance, unity and proportion all apply to a wall as much as to a garden bed.
Planting on and around the wall
A new level creates a fresh planting area at the top and a sheltered strip at the base. Choose plants that suit the sun, wind and soil at each level. Keep large tree roots away from the wall footing. Trailing plants can soften a hard face and make a tall wall feel smaller.
If the wall sits near a pool or lawn, plant choice needs extra care. Our article on planting around your pool and lawns covers what tends to work in those spots. Remember that NSW guidance also says council approval may be needed if trees or other vegetation are pruned or removed for the works.
When to bring in a professional
A low garden edge is a reasonable weekend project for many homeowners. Taller walls, boundary walls and walls carrying a load are a different story. They need correct footings, drainage and often an engineer’s design. Mistakes can affect your neighbour as well as your own garden.
An experienced team will check levels, approvals and soil conditions before quoting. They can also coordinate with the engineer and the council. If you are weighing it up, read our thoughts on why you should use professional landscapers for larger jobs. A wall is meant to last decades, so getting it right the first time pays off.
Frequently asked questions
How high can a retaining wall be without a permit in WA?
Many WA councils, including Albany and Wanneroo, require a building permit for walls over 500mm. A lower wall can still need one if it affects a boundary or drainage. Always confirm with your local council before you start.
Is a retaining wall exempt development in NSW?
It can be, if it meets every standard in the Exempt and Complying Development Codes policy. These include a 600mm height limit, a 1m setback from each lot boundary and at least 2m between retaining walls on the same site. If it misses any standard, you need approval first.
Who pays for a retaining wall on the boundary?
WA council guidance says each owner retains soil from their own earthworks. Where both owners changed levels, they should negotiate a fair split. Councils generally treat cost disputes as a civil matter.
Can I use treated pine sleepers on the boundary?
It depends on your council. The City of Albany does not permit timber materials on a property boundary. Check local rules before buying materials.
Rules for retaining walls differ between states and councils and can change. Check current requirements with your local council or a building surveyor before you build.
