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Retaining Wall Calculator
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Retaining Wall Calculation Formula
Courses: ceil(Wall Height ÷ Sleeper Height)
Sleepers per Course: ceil(Wall Length ÷ 2.4)
Total Sleepers: Courses × Sleepers per Course
Posts: ceil(Wall Length ÷ Post Spacing) + 1
Concrete per Post: 0.05 m³
Total Concrete: Posts × 0.05 m³
Sleepers per Course: ceil(Wall Length ÷ 2.4)
Total Sleepers: Courses × Sleepers per Course
Posts: ceil(Wall Length ÷ Post Spacing) + 1
Concrete per Post: 0.05 m³
Total Concrete: Posts × 0.05 m³
Note: Sleeper length assumed at 2.4 m standard. Concrete per post based on 450 mm diameter × 300 mm deep footing.
Retaining Wall Calculator — Sleepers, Blocks & Materials
The average Australian new home build uses 20–30 cubic metres of concrete (HIA, 2025), and retaining walls are a major part of site preparation on sloping blocks. Getting materials right avoids costly re-orders and schedule delays.
Timber Sleeper Retaining Wall — Materials by Height
| Wall Height | Sleepers per m | Steel Posts (per m) | Concrete per Post |
|---|---|---|---|
| 200mm (1 sleeper) | 0.5 | 0.63 (1.6m spacing) | 0.02 m³ |
| 400mm (2 sleepers) | 1.0 | 0.63 | 0.03 m³ |
| 600mm (3 sleepers) | 1.5 | 0.63 | 0.04 m³ |
| 800mm (4 sleepers) | 2.0 | 0.63 | 0.05 m³ |
| 1.0m (5 sleepers) | 2.5 | 0.63 | 0.06 m³ |
Concrete Block Retaining Wall — Materials by Height
| Wall Height | Blocks per m | Reo Bar per m | Core Fill per m |
|---|---|---|---|
| 400mm (2 courses) | 5.0 | 0.8m N12 | 0.008 m³ |
| 600mm (3 courses) | 7.5 | 1.2m N12 | 0.012 m³ |
| 800mm (4 courses) | 10.0 | 1.6m N12 | 0.016 m³ |
| 1.0m (5 courses) | 12.5 | 2.0m N12 | 0.020 m³ |
| 1.2m (6 courses) | 15.0 | 2.4m N12 | 0.024 m³ |
Tips for Retaining Wall Projects
- Walls over 1.0m high require engineering design in most Australian states.
- Always install ag-pipe drainage behind the wall with geofabric filter cloth.
- Allow 0.3 m³ of drainage gravel per lineal metre of wall.
- Check with your local council — retaining walls may need a development application.
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