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20mm clean crushed drainage aggregate is the free-draining backfill that sits behind a retaining wall — it channels groundwater down to the ag pipe and relieves the water pressure that causes walls to fail. By the 25kg bag or the cubic metre. Delivered Australia-wide by Retaining Walls Direct.
Written and product-checked by the Retaining Walls Direct team — supplying retaining wall drainage products across Australia. Last updated: June 2026.
Packed behind a concrete sleeper wall between the posts and the geotextile fabric, the aggregate creates the drainage zone. Without it, even a perfectly built wall will eventually fail. See the drainage guide.
As a guide, allow roughly 0.15–0.20m³ per lineal metre of wall (300mm drainage zone). Use the retaining wall calculator for your dimensions.
| Material | 20mm clean crushed drainage aggregate |
|---|---|
| Supply | 25kg bag · 1m³ (cubic metre) |
| Use | Free-draining backfill behind retaining walls |
| Brand | Retaining Walls Direct |
Pair with ag pipe and geo matting, or a complete drainage kit.
Get a quote or contact the team.
How much do I need?
About 0.15–0.20m³ per lineal metre of wall — use the calculator.
Bag or bulk?
25kg bags for small jobs/top-ups; 1m³ for full walls.
Can you deliver to me?
We deliver across most of Australia. Send your details for a quote.
