Retaining wall heights and approvals

Retaining wall heights: when you need approval and an engineer

Small retaining walls may need no approval in NSW, but beyond a modest height they need approval and usually an engineer. This guide covers the height thresholds and the other conditions that apply.

Retaining walls hold back soil where ground levels change, and small garden bed walls can usually be built without approval. Taller walls carry far more load, so NSW rules treat them very differently. This guide explains how height sets the approval path and when an engineer should be involved.

Small walls: the exempt pathway

Earthworks and retaining walls can be exempt development under Part 2, State Environmental Planning Policy (Exempt and Complying Development Codes) 2008. According to the NSW Planning Portal, once cut, fill or a supporting wall goes past 600 mm relative to natural ground level, it can be done as complying development. In practice, that makes 600 mm the ceiling for exempt walls.

Height is not the only test. According to the Planning Portal, an exempt retaining wall must also:

Not be on or for a heritage item or draft heritage item.
Sit in the back yard where the property lies within a heritage conservation area.
Keep a 40 m or greater distance from any natural waterbody.
Not redirect surface or ground water, or wash sediment, onto a neighbouring property.
Leave a horizontal gap of 2 m or more to the next retaining wall.
Be structurally sound and comply with the building code.

The 2 m separation stops people from building one tall wall as a series of short ones stacked close together. Tiered walls interact. The lower wall carries load from the upper one unless they are far enough apart.

Taller walls need approval

Above the exempt limit, a retaining wall needs approval. Separate controls on cut, fill, retaining, structural support and drainage appear in the Housing Code of the Codes SEPP. A wall that satisfies them may be approved by complying development certificate (CDC), often as part of a bigger project such as a house, extension or pool. If not, council assesses a development application (DA), and a construction certificate comes next.

Walls near boundaries can face tighter limits. Our article on Retaining walls on the boundary: neighbours, footings and access covers the extra issues those walls raise.

When you need an engineer

The building code requires retaining structures to resist earth pressure, water pressure and other loads safely. The National Construction Code points to AS 4678, the Australian Standard for earth-retaining structures, which covers walls from 800 mm up to 15 m high.

As a practical rule, expect to need a structural engineer's design where:

The wall is above the exempt height.
It supports a building, driveway, pool or other structure above it.
Vehicles, sheds or stored materials will sit near the top of the wall, adding load.
The wall sits near a boundary or next to a neighbour's buildings.
The soil is reactive clay, fill or wet, or the site slopes steeply.
Walls are tiered.

Proprietary block and sleeper systems come with design tables, but those tables have limits on height, soil, slope and loads. If your site is outside them, an engineer needs to design the wall.

Drainage belongs in the design

Most retaining wall failures relate to water, not the wall material. An engineer's design should show how water behind the wall is collected and where it is discharged. Our guide on Why retaining walls fail: drainage and backfill basics explains what a good system includes.

Inspections and records

Depending on the approval, the certifier or the engineer may need to see footings and reinforcement before concrete is poured. Keep the engineer's certificate and photos of drainage before backfill. They are useful if questions come up later, including when selling.

CertifiBuild certifies retaining walls as part of Class 1 and Class 10 projects across NSW. A plan assessment can tell you whether your wall fits a CDC before you lodge.

Local help across NSW

CertifiBuild certifies Class 1 and Class 10 work in 39 council areas. Local rules on these council pages are a good place to start: Randwick City Council, Burwood Council, Fairfield City Council, City of Canada Bay, Hunter’s Hill Council, Campbelltown City Council.

Suburb pages with local planning notes: Clovelly, Enfield, Fairfield, Five Dock, Henley, Ingleburn, Liverpool, Marsden Park, McGraths Hill, McMahons Point. You can also browse every service area.