A concrete sleeper retaining wall is one of the most durable and cost-effective ways to manage sloped ground, create usable garden terraces, or protect your property from soil movement. Done right, it will last 50 years or more with virtually zero maintenance.

This guide walks you through the entire process — from planning and materials through to the final backfill.

What You'll Need

Before you start, gather your materials:

• Concrete sleepers — 50 MPa high-strength, in your chosen finish (plain, charcoal, woodgrain or stackstone)
• Galvanised steel posts — H posts or C posts depending on wall height and design
• Drainage aggregate — 20mm blue metal or drainage gravel
• Geotextile fabric — to prevent soil migration into the drainage layer
• Concrete — for setting posts (minimum N20 mix)
• Compactable fill — for backfilling behind the wall
• Weep holes or ag pipe — for water management

As a rule of thumb, for every 1 metre of exposed wall height you need approximately 1 metre of post embedded in the ground. A 1.2m high wall needs posts set at least 1.2m deep.

Step 1: Plan and Check Regulations

Retaining walls over 1 metre in height typically require a building permit in Victoria. Check with your local council before you start. You'll also want to:

• Mark out the wall line with string and stakes
• Identify any underground services (call Dial Before You Dig — 1100)
• Confirm the wall is set back from property boundaries as required
• Consider drainage from neighbouring properties

Step 2: Excavate and Set Your Posts

Excavate the post holes to the required depth. For a 1.2m wall, you're digging roughly 1.2–1.5m deep. Use a post-hole digger or hire a mini excavator for longer runs.

Post spacing for concrete sleepers is typically 1.8m to 2.4m centre-to-centre, depending on the sleeper length and wall height. Standard 2.4m sleepers suit 1.8m post spacing.

Set each post plumb and in line. Pour concrete around the post and allow it to cure for at least 48 hours before loading the sleepers. Brace posts during curing if needed.

Step 3: Lay the Drainage Layer

Before you start stacking sleepers, lay your drainage infrastructure:

1. Place geotextile fabric against the excavated face
2. Add a 150–200mm layer of drainage aggregate at the base
3. Install ag pipe (slotted, sock-wrapped) along the base of the wall, sloping to an outlet
4. Fold the geotextile over the top of the aggregate to prevent soil contamination

Good drainage is the single most important factor in retaining wall longevity. Hydrostatic pressure from trapped water is the number one cause of wall failure.

Step 4: Install the Sleepers

Slide the first sleeper into the post channels at ground level. Work along the full length of the wall before moving up to the next course.

Key tips:

• Check each sleeper is level as you go — small errors compound as you build up
• For walls over 3 courses, consider a slight batter (lean back into the slope) of 1:10
• Weep holes can be created by leaving small gaps between sleepers or drilling through — one weep hole per 1.8m of wall is a good guide
• Stagger vertical joints between courses for a stronger, more attractive finish

Continue stacking sleepers until you reach the desired height.

Step 5: Backfill and Compact

Backfill in 200–300mm layers, compacting each layer before adding the next. Use a plate compactor for larger jobs. Do not use expansive clay soils directly behind the wall — use a free-draining fill or the drainage aggregate.

Leave the top 300mm for topsoil and planting if required.

Step 6: Finish and Cap

Once backfilled, you can add a capping sleeper laid flat on top for a clean finish, or leave the posts exposed for a more industrial look. Seal any exposed cut ends of posts with a cold galv spray to prevent rust.

Common Mistakes to Avoid

• Insufficient post depth — the most common cause of wall failure
• No drainage — leads to hydrostatic pressure and wall movement
• Skipping the permit — can result in costly demolition orders
• Using the wrong post type — C posts and H posts have different load capacities; match the post to your wall height and soil conditions

How Much Does It Cost?

Costs vary by wall height, length and finish, but as a rough guide for a standard 1.2m plain concrete sleeper wall in Melbourne:

• Materials only: $180–$250 per lineal metre
• Installed (trade contractor): $350–$600 per lineal metre

Charcoal, woodgrain and stackstone finishes add a small premium but significantly improve the aesthetic result.

Get a Quote

FPM Building Supplies stocks a full range of 50 MPa concrete sleepers and galvanised steel posts from our Epping warehouse, with Melbourne-wide delivery available. Contact our team for trade pricing and project advice.