How high can a retaining wall be before it needs approval?

It is set by your local council and commonly sits under a metre, with the threshold dropping further where the wall is near a boundary or carries a surcharge such as a driveway or a building above it. Because it is local and because the surcharge rules change the answer, the council is the only reliable source.

Why do retaining walls fail?

Overwhelmingly drainage. Water behind a wall is heavy and it adds pressure the wall may not have been designed for. A wall without a drain behind it, with the drain blocked, or with the drain discharging nowhere, is the standard post-mortem — which is why the drainage question is the one to ask before the material question.

Who to hire to build a retaining wall

Short answer

A landscaper for a low garden wall, and a builder working to an engineer's design for anything above the height your council sets as the approval threshold — commonly under a metre, but it varies. Retaining walls fail by sliding, overturning and drainage failure, and all three are design problems rather than construction ones.

Plan itThere is time to get more than one quote, which is where the money is.

When it is someone else

Calling the wrong trade costs an attendance fee to be told so. These are the cases where this problem belongs to someone other than a gardener or landscaper.

a structural or civil engineer
the wall is above your council's threshold, is near a boundary or a structure, or retains a driveway. The design is what the approval is given for.
your council
before quoting. The height threshold, setbacks and whether a surcharge behind the wall changes the requirement are all local.

What to do before anyone arrives

Measure the height you actually need to retain, at the highest point, and find your council's threshold.
Find out what is behind and above the wall — a driveway, a pool, a building or a neighbour's land all count as surcharge and change the engineering.
Locate services. Retaining walls involve excavation along a line and that is where services run.
Talk to the neighbour if it is anywhere near the boundary.

What to ask when you book

Does this need approval and engineering at this height, and who is obtaining it?
What drainage is behind the wall — agricultural drain, aggregate, geotextile, weep holes?
What is the wall footing, and how is it tied back?
What happens to the surcharge from the driveway above?

What changes the price

No dollar figures here: this directory holds no price data and an invented range is worse than none. What follows is what makes one of these jobs cost more than the same job next door, which is the part you can actually use when comparing quotes.

Height, length and what is being retained.
Engineering and approval.
Drainage behind the wall, which is not optional and is what most failed walls left out.
Material: timber sleepers, concrete sleepers, blocks, stone or poured concrete.
Access for excavation and materials.

What you can do yourself

Is this licensed work?

Retaining walls above a height threshold set by each council generally require building approval and engineering design, and the work falls inside building work licensing. Walls on or near a boundary have additional rules and usually involve the neighbour.

There is no national register. Search the licence number with the regulator for the state the work is happening in.

NSWNSW Fair Tradingbuilders, electricians, plumbers and specialist trades
VICBuilding and Plumbing Commission, and Energy Safe Victoria for electricalbuilding practitioners and plumbers; electricians are Energy Safe Victoria
QLDQueensland Building and Construction Commission (QBCC)building and most trade contractor licences
WABuilding and Energybuilders, electricians, plumbers and gas fitters
SAConsumer and Business Servicesbuilding work contractors and supervisors
TASConsumer, Building and Occupational Services (CBOS)building and occupational licences
ACTAccess Canberraconstruction occupations licensing
NTNT Government building practitioner registrationbuilding practitioners and electrical workers

Licensing thresholds and certificate requirements differ by state and change with amending regulation, so this page describes the mechanism rather than quoting a figure. The regulator’s own page is the current answer.

Common questions

Who should I hire for a retaining wall to build: A landscaper for a low garden wall, and a builder working to an engineer's design for anything above the height your council sets as the approval threshold — commonly under a metre, but it varies. Retaining walls fail by sliding, overturning and drainage failure, and all three are design problems rather than construction ones.
How high can a retaining wall be before it needs approval?: It is set by your local council and commonly sits under a metre, with the threshold dropping further where the wall is near a boundary or carries a surcharge such as a driveway or a building above it. Because it is local and because the surcharge rules change the answer, the council is the only reliable source.
Why do retaining walls fail?: Overwhelmingly drainage. Water behind a wall is heavy and it adds pressure the wall may not have been designed for. A wall without a drain behind it, with the drain blocked, or with the drain discharging nowhere, is the standard post-mortem — which is why the drainage question is the one to ask before the material question.

Find a gardener or landscaper near you

2,259 gardeners & landscapers in this directory, ranked on published evidence rather than on advertising.

Who to hire for

General information about who does what, not advice about your specific job. Licensing, consumer law and council rules differ by state and change; the regulator for your state is the current source. More guides to hiring a tradesperson.