If you're planning a retaining wall in Melbourne or anywhere in Victoria, the permit question is usually the first one you'll face. The rules aren't complicated, but there are enough exceptions to catch people out.

Here's a clear breakdown of the height limits, the exceptions, and what you need to do to stay on the right side of your council.

The Short Answer: 1 Metre

Under the Building Regulations 2018 (Victoria), a retaining wall that retains 1 metre or more of soil requires a building permit. This is the baseline rule that applies across the state.

Note that this is the height of soil retained — not the total height of the wall above ground. A wall that sits on flat ground and retains a raised garden bed is measured differently to a wall cut into a slope.

The Exceptions That Can Require a Permit for Shorter Walls

Even if your wall is under 1 metre, you may still need a permit if:

1. The wall is near a boundary Walls within 1.5 metres of a property boundary may require a permit regardless of height, particularly if they could affect drainage or stability on the neighbouring property.

2. The wall is near a building A retaining wall within 1.5 metres of any building (yours or a neighbour's) may require a permit due to the potential for soil movement to affect footings.

3. There's surcharge loading If a driveway, vehicle path, shed or other structure sits above the wall, the additional load changes the engineering requirements — and often triggers a permit requirement even for shorter walls.

4. The wall is in a designated area Flood zones, bushfire-prone areas, erosion-prone land and land subject to inundation all have additional requirements. Check your property's overlay status on the relevant council planning map.

5. The wall affects a drainage easement or sewer Any structure near a drainage easement or sewer line will require approval from the relevant water authority, regardless of height.

6. Your council has lower thresholds Some Melbourne councils have adopted lower thresholds than the state minimum. Always check with your specific council — Nillumbik, Yarra Ranges and some inner-city councils have stricter requirements.

What Counts as "Retaining Height"?

This is where people sometimes get confused. The retained height is the vertical distance between the soil level on the high side and the soil level on the low side of the wall.

If you're building a wall into a slope:

• The high side is the soil level behind the wall
• The low side is the finished ground level in front of the wall
• The retained height is the difference between these two levels

The exposed height of the wall above the low-side ground level is what most people think of as the wall height — and for a wall built into a slope, this is usually the same as the retained height.

Tiered Walls

Some homeowners try to avoid the permit threshold by building two or more shorter walls instead of one taller wall. This can work, but councils are wise to it.

If the horizontal distance between the tiers is less than the combined height of the walls, most councils will treat the system as a single wall for permit purposes. A general rule of thumb: the setback between tiers should be at least equal to the height of the lower wall.

Always check with your council before designing a tiered system to avoid the permit threshold.

What a Building Permit Involves

If your wall does require a permit, the process involves:

1. Engaging a registered building surveyor to assess and issue the permit
2. Providing structural engineering computations — these must be prepared by a registered structural engineer and demonstrate that the wall design is adequate for the soil conditions and retained height
3. Submitting a site plan showing the wall location, dimensions and relationship to boundaries and structures
4. Inspections — typically at the post-hole stage (before concrete is poured) and at completion

FPM Building Supplies provides engineering computations for our concrete sleeper retaining wall systems — available for download on our Engineering page. These are accepted by most Victorian councils as supporting documentation.

Maximum Wall Heights for FPM Concrete Sleeper Systems

Our engineering computations cover the following maximum wall heights:

75mm Concrete Sleepers:

• 1.8m post → 600mm max wall height
• 2.4m post → 900mm max wall height
• 3.0m post → 1200mm max wall height
• 3.6m post → 1500mm max wall height
• 4.2m post → 1800mm max wall height

100mm Concrete Sleepers:

• 2.4m post → 1050mm max wall height
• 3.0m post → 1350mm max wall height
• 3.6m post → 1650mm max wall height
• 4.2m post → 1950mm max wall height

Full tables are available on our Engineering & Specifications page.

The Bottom Line

For most straightforward residential retaining walls in Victoria:

• Under 1 metre retained height, away from boundaries and structures: no permit required
• 1 metre or more retained height: building permit required
• Near a boundary, building or with surcharge loading: check with your council regardless of height

When in doubt, a quick call to your local council's building department will give you a definitive answer for your specific situation. It's a much better outcome than building without a permit and facing a demolition order.

FPM Building Supplies is based in Epping and supplies concrete sleepers, steel posts and retaining wall materials across Melbourne. Call us on 0431 235 919 for product advice and trade pricing.