About this calculator
Estimate Terraforce L11 or Löffelstein retaining blocks, drainage stone and drain pipe for a garden or landscape wall, and check the wall height against the block maker’s limits.
How it’s calculated
Blocks = wall face area (including a buried course) × blocks per m²: 11 for Terraforce L11 (225 mm courses) and 9.5 for Löffelstein L300, L500 and L750 (170 mm courses), from the makers’ datasheets. The base and drainage zone are length × width × depth.
Worked example
With these inputs:
- Wall length
- 10 m
- Exposed wall height
- 900 mm
- Block system
- Terraforce L11 (11 per m²)
- Retained soil
- Firm clay or compact silt
- Ground above the wall
- Level
- Wall inclination
- 70°
- Add a buried first course
- Yes
- Base trench width
- 600 mm
- Base depth
- 150 mm
- Drainage zone behind wall
- 300 mm
- Waste allowance
- 5%
the result is:
- Wall blocks
- 130 blocks
- Courses
- 5 of 225 mm
- Wall face area (incl. buried course)
- 11.25 m²
- Base material
- 0.9 m³
- Drainage stone
- 3.38 m³
Tips from the trade
- Infraset says Löffelstein walls over 1.2 m need an engineered design and plans submitted to the local authority. Terraforce publishes the maximum unreinforced height for each soil, slope and wall angle; anything higher needs an engineer.
- Timber sleeper and gabion walls are other options; count those by the sleeper or basket.
- Drainage behind the wall is as important as the blocks. Water pressure is what pushes walls over.
- Step the base for walls running up a slope.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and SANS 10400 (the National Building Regulations) and your local municipality before ordering.