Do You Need Approval for a Retaining Wall in Western Australia?

In Western Australia, retaining wall approval requirements are governed by the Building Act 2011 and Building Regulations 2012. WA has some of the lowest height thresholds for building permits in Australia — walls over 500mm generally require approval. This guide covers the general rules — always confirm with your local council or a registered building surveyor before starting work.

Height Limits — The General Rule

• Under 500mm: Generally exempt from a building permit on standard residential land
• 500mm – 1m: Requires a building permit from a registered building surveyor in most cases
• Over 1m: Requires a building permit and almost always requires structural engineering drawings and certification

Important: WA's 500mm threshold is lower than most other states. Many homeowners are surprised to find they need a permit for what appears to be a modest garden wall. Always check before you dig.

When Does the Exemption Not Apply in WA?

Even walls under 500mm may require approval if they are:

• Within 1.5m of a boundary
• Within 1.5m of a building, pool, or structure
• In a special control area or heritage zone
• On a steep or unstable site
• Part of a tiered system where combined retained height exceeds 500mm

Perth-Specific Rules

Perth metropolitan councils operate under the City of Perth's planning framework and the state Building Regulations. Key points for Perth homeowners:

• The City of Perth, Stirling, Joondalup, and Swan councils all require building permits for walls over 500mm
• Coastal councils (Cottesloe, Fremantle, Rockingham) may have additional requirements near waterways and coastal zones
• Hills councils (Kalamunda, Mundaring) have stricter controls due to slope, bushfire, and soil instability
• Check your local council's planning scheme and any special control areas via the WA Planning Portal (planning.wa.gov.au)

Do You Need an Engineer in WA?

A structural engineer's certificate is required when:

• The wall exceeds 1m in retained height
• The building surveyor requires it as a condition of the permit
• The site has reactive soil, loose sand, or poor drainage (common in Perth's coastal suburbs)
• The wall supports a surcharge load (driveway, structure, or vehicle access above)
• The wall is near a boundary or building

Perth's sandy coastal soils present unique challenges — post embedment depth is critical in loose sand, and drainage is essential to prevent washout behind the wall. Our H-Beam UC steel posts and 200x100mm heavy duty concrete sleepers are the standard specification for engineer-designed walls in WA. Download our technical drawings and load tables to provide to your engineer.

Sandy Soils in Perth — What You Need to Know

Much of Perth's coastal plain sits on loose, free-draining sand. While drainage is less of a concern than in clay-heavy states, sandy soils provide less lateral resistance to posts — meaning posts need to be set deeper than in clay. As a rule of thumb, increase post embedment depth by 20–30% compared to standard clay soil specifications when building on Perth's coastal sands.

Practical Steps for WA Homeowners

1. Measure your retained height and note proximity to boundaries and structures
2. Check your property for special control areas via the WA Planning Portal
3. If under 500mm and away from boundaries — likely exempt, but confirm with your local council
4. If over 500mm — engage a registered building surveyor to obtain a building permit
5. If over 1m or on unstable soil — engage a structural engineer before designing the wall

Delivering to Perth & WA

We deliver concrete sleepers and steel posts to Perth metro and regional WA. Visit our Retaining Walls Perth page for local delivery information, or book a free quote with delivered pricing to your postcode.