Step-by-Step Guide to Building a Concrete Sleeper Retaining Wall

Phase 1: Planning and Preparation

1. Determine the Purpose and Height:

   • Clearly define why you need the retaining wall (e.g., manage sloping land, create a level area).
   • Accurately measure the height difference you need to retain. This will significantly impact the materials required and the complexity of the project.

2. Design and Layout:

   • Sketch out the planned location and length of the wall.
   • Consider any curves or corners in your design.
   • Think about drainage requirements (see Step 9).
   • Important: For walls exceeding a certain height (typically 600mm to 1m, check your local council), you will likely need engineered plans.

3. Check Local Council Regulations and Permits:

   • Contact your local council in Melbourne to understand their specific rules regarding retaining walls. This includes height restrictions, setback requirements, and whether a permit is necessary.
   • Obtain any required permits before commencing work.

4. Mark Out the Wall Location:

   • Use stakes or pegs and string lines to clearly mark the exact location and line of your retaining wall. Ensure its straight and in the desired position.

5. Call Before You Dig (Dial 1100 in Australia):

   • Before digging any holes, it's crucial to contact "Dial Before You Dig" to locate any underground services like gas, electricity, or water pipes. This is essential for safety.

6. Gather Materials and Tools:

   • Concrete Sleepers: Calculate the number needed based on the wall's length and height. Choose the desired style and strength.
   • Steel Posts (H or C Section): Determine the required length based on the wall height plus the depth needed for setting in concrete (typically a third of the above-ground height). The spacing between posts is usually the length of the sleepers (e.g., 1.5m or 2m).
   • Concrete Mix: For setting the posts. Calculate the amount needed based on the number of posts and hole size.
   • Gravel or Crushed Rock: For drainage behind the wall.
   • Geotextile Fabric: To prevent soil from washing through the drainage material.
   • Spirit Level: Long and short levels for accuracy.
   • Measuring Tape: For accurate measurements.
   • Shovel and Post Hole Digger (or Auger): For digging post holes.
   • Wheelbarrow or Mixing Tub: For mixing concrete.
   • Gloves, Safety Glasses, and Appropriate Clothing: For personal protection.
   • Rubber Mallet or Hammer and Block of Wood: For tapping sleepers into place (if needed).
   • String Line and Pegs: For marking the wall line.
   • Optional: Laser level for more precise leveling.

Phase 2: Installation

7. Dig Post Holes:

   • Following your marked line, dig the post holes at the determined spacing. The depth should be sufficient to securely anchor the posts (typically around one-third of the above-ground height).
   • Ensure the holes are wide enough to accommodate the steel posts and concrete.

8. Set the First Post:

   • Place the first steel post into the hole.
   • Use a spirit level to ensure the post is perfectly vertical in both directions.
   • Pour the concrete mix around the base of the post, ensuring it's well compacted to eliminate air pockets.
   • Use temporary bracing (e.g., timber planks secured to the post and ground) to hold the post in position while the concrete sets.

9. Set Subsequent Posts:

   • Using a string line stretched tightly between the first post and the intended location of the last post, align the remaining post holes.
   • For each subsequent post, place it in the hole and use a spirit level to ensure its vertical.
   • Crucially, also use a sleeper as a temporary spacer between the newly placed post and the previous one to ensure the correct spacing and that the tops of the posts are level. This will make inserting the sleepers easier later.
   • Pour concrete around each post and brace as needed.
   • Allow the concrete to fully cure according to the manufacturer's instructions (usually 24-48 hours) before proceeding.

10. Install the Concrete Sleepers:

    • Once the concrete has cured and the posts are firmly set, you can begin installing the concrete sleepers.
    • Start from the bottom. Carefully slide the first sleeper into the slots or channels of the steel posts. You may need to gently tap it into place using a rubber mallet or a hammer and a block of wood to avoid damaging the sleeper.
    • Ensure the sleeper is level along its length using a spirit level.
    • Continue adding sleepers one by one, working your way up the wall. Ensure each sleeper sits securely within the post channels.

Phase 3: Backfilling and Drainage

11. Install Drainage:

    • This is a critical step to prevent water buildup behind the wall, which can cause pressure and lead to failure.
    • Lay down a layer of geotextile fabric behind the wall, extending up the back of the sleepers.
    • Pour a layer of gravel or crushed rock behind the wall, covering the base and extending upwards. The depth of this drainage layer will depend on the site conditions and wall height (typically at least 200-300mm).
    • Fold the geotextile fabric over the top of the gravel to prevent soil from filtering in.

12. Backfill with Soil:

    • Carefully backfill the remaining area behind the wall with soil, compacting it lightly in layers to avoid putting excessive pressure on the wall. Be careful not to damage the sleepers or posts during this process.

Phase 4: Finishing Touches

13. Capping (Optional):

    • You can add capping to the top of the wall for a more finished look and to protect the top sleepers. Options include timber, concrete, or other suitable materials.

14. Landscaping:

    • Once the wall is complete, you can landscape the area around it as desired, such as planting or adding other features.

Important Considerations for Melbourne, Victoria:

• Soil Type: Melbourne has various soil types. Understanding your soil will help in designing the appropriate drainage system.
• Rainfall: Melbourne can experience significant rainfall. Ensure your drainage is adequate to handle potential water runoff.
• Bushfire Prone Areas: If your property is in a bushfire-prone area, ensure the materials you use comply with local regulations. Concrete sleepers are generally a good choice in these areas.