SRW SYDNEYRETAINING WALLS
FREE PRELIMINARY TOOL • RETAINING WALL CHECK

Retaining Wall Calculator.

For low garden and yard walls up to 1.5 m, answer a few practical questions to receive an indicative assessment of loading, suitable wall systems and approximate proportions.

This uses the standard earth-pressure method behind the Australian earthworks & retaining standards (AS 4678). It's deliberately a rough guide only for low walls — not a design, and not a certificate. Walls taller than about 1.5 m, or close to a building, road or boundary, carry more risk and need proper engineering — this tool will tell you when you're in that territory.

Tell me about your wall

Your retaining wall

Not sure about a value? Leave the sensible default. The diagram below explains what each question means.

active wedge building (higher side) distance behind wall wall height global slip-circle
The soil in the red wedge tends to slide with the wall. A building on the higher side, sitting in that zone, both loads the wall and can fail with it — and the whole slope can rotate on a deep slip-circle. That's engineer territory, not a rule of thumb.
Measured from the lower ground up to the top of the retained soil. This tool covers low walls up to 1.5 m.
900 mm
Anything sitting on the soil behind pushes harder on the wall — vehicles most of all.
If it sits inside the soil wedge that bears on the wall, the wall has to carry the building's load and the building can be undermined if the wall moves — that's a designed wall, not a rule of thumb.
2.0 m
A structure on the lower side is a lesser risk than a load on top — but the wall partly protects it, so it still matters.
Clay holds water and pushes harder; sand and gravel drain and behave better.
"Engineered fill" is soil that's been built up in thin layers and compacted properly. "Loose or natural" is existing ground, or fill that was just tipped in.
A gravel zone and an ag-drain (slotted pipe) behind the wall let water escape. Without it, water builds up and can roughly double the push on the wall.
Indicative result only

Wall height
Estimated push (per metre of wall)
Estimated overturning demand
Rough estimates from typical soil values — your real ground will differ. This is why a proper review matters.

What sort of wall, and roughly what size?

Indicative options for a wall of this height and loading — an example of what similar walls use, not a recommendation for your wall.

Timber sleeper

Set treated posts in concrete footings, stack treated sleepers between them, then backfill with free-draining gravel behind an ag-drain.

Segmental block

Interlocking concrete blocks on a compacted granular pad, stepped back as they rise, with a gravel drainage zone — geogrid soil reinforcement added when the wall works harder.

Reinforced concrete

An L-shaped reinforced concrete wall (base + upstand) cast on firm ground; the weight of soil over the heel holds it down. Waterproof the back, drain behind.

Gravity / mass

A heavy mass-concrete or large-stone wall that resists purely by its own weight — simple, but needs a wide base and good drainage with weep holes.

Suggested build method (minor wall)

Because this wall is under 800 mm it's a minor landscaping wall, below the formal scope of AS 4678. A typical sequence for a timber-sleeper version:

  1. Set out the line and dig post holes — depth about equal to the wall height, roughly 300 mm diameter, at about 1.5 m centres.
  2. Stand treated (H4/H5) posts plumb and concrete them in; let the concrete cure before loading.
  3. Stack treated sleepers between the posts, fixing each course down.
  4. Lay an ag-drain (slotted pipe) along the base behind the wall, falling to an outlet.
  5. Backfill behind with free-draining gravel wrapped in geofabric — never plain clay against the wall.
  6. Finish the top so surface water runs away from the wall, not over it.

⚠ Please read — this is not a design or a certificate

This free tool makes safe, generic assumptions and cannot see your actual site. It does not account for:

  • Your real soil, ground-water, and how well the fill is actually compacted
  • Slopes, surcharges, services, trees, or footings near the wall
  • Overall slope stability — the whole mass rotating on a deep "slip-circle" — which governs when there's a load on top or sloping ground
  • Foundations, passive resistance at the toe, and what the wall bears on
  • Council / NCC requirements and whether approval is needed

Any size shown is an indicative example of what similar walls often use — it is not a recommendation for your wall. Do not order materials or start work from this result. A registered structural engineer should review your specific situation.

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