Permits · Retaining Walls

Retaining wall permit rules in WA — the 500 mm rule explained

By WAPermitCheck · Updated January 2025 · 6 min read

Retaining walls are one of the most common causes of permit trouble in Perth. Many homeowners assume the exemption threshold is 1 metre — as it is in some other states. In Western Australia, the threshold is 500 mm (half a metre).

Key fact: The retaining wall permit exemption in WA is 500 mm measured from the bottom of the footing to the top of the wall — NOT from ground level to the top. Source: City of Bayswater — Fences and Retaining Walls.

The three conditions that must ALL be met for exemption

All three must be true simultaneously

✓Height ≤ 500 mm: The wall retains ground no more than 500 mm. Measured from the base of the footing to the top of the wall.

✓Not on the boundary: The wall is not retaining the adjoining property's ground — not a cut to the land on the boundary where your neighbour's land is higher.

✓Not supporting other structures: The retaining wall is not associated with other building work — for example, it is not the foundation of a patio, carport, or deck.

The "supporting structures" trap

A common Perth scenario: you're building an alfresco and to level the area, you build a small retaining wall on one side. Even if that wall is only 400 mm high, because it's structurally associated with the patio, the exemption doesn't apply.

Practical rule: If you're building a retaining wall at the same time as another permitted structure, assume you need a permit and budget for it.

Engineer certification: when you need it

For walls over approximately 800 mm, Perth councils typically expect engineer-certified structural designs as part of the permit application. Cost: $500–$2,000 depending on complexity and wall length. For walls between 500 mm and 800 mm, engineering is not always mandatory but is strongly recommended on Perth's sandy and reactive clay soils.

Retaining wall costs in Perth 2025

Limestone blocks (budget): $400–$700 per linear metre
Concrete blocks or sleepers (mid-range): $700–$1,200 per lm
Rendered block or feature stone (premium): $1,200–$2,000 per lm

Drainage behind the wall adds 25–30% to material cost. Don't let a tradie quote without drainage — a retaining wall without proper drainage will fail within 3–5 years in Perth conditions.

Check your retaining wall instantly

Enter your wall height and length — get a permit verdict and a Perth-adjusted cost estimate.

Use the calculator →

Sources City of Bayswater — Fences and Retaining Walls · City of Gosnells — Do I need a permit? · Building Act 2011 (WA) · Dividing Fences Act 1961 (WA) · Building Commission WA · Master Builders WA 2025