Robust Retaining Wall Block

The Robust Retaining Wall Block, developed and manufactured by Bosun, is an innovation in the retaining wall market. The block features new patented design elements with better weight distribution and height tolerances compared to standard retaining wall blocks.

A critical aspect with retaining wall blocks is consistency in block heights. SANS 508, (the official South African specification for retaining wall blocks) specifies dimensional differences of not more than ±3mm. The Bosun Robust Block guarantees these height tolerances or your money back. If there are any dimensional inaccuracies, it is at the back of the block that can’t be seen and it doesn’t have any structural influence.

The Robust retaining wall block can be used in either a closed or open face formation, with the open face being extremely popular due to the economic advantage of using less blocks and saving on costs. At 5.1 blocks/m² using an open formation, the Robust Block is one of the most competitive in the market.

An open face formation can be transformed into a closed face by using a cost-effective slider between the blocks. The slider prevents soil erosion between the blocks and most importantly on the top row – regardless of formation. Additionally, a closed face formation using the slider can improve the aesthetics of the wall as it promotes plant growth within the retained soil.

Bosun Robust Block single product image

Robust Block

Slider for Robust Block single product image

Robust Slider

Image showing the back of the Robust Block

Special V shaped stiffeners

The Bosun Robust Block has a superior crushing strength compared to most standard concrete retaining blocks. The crushing strength is derived from various design elements including the unique V shape stiffeners in the block.

Because of the superior crushing strength, the construction of retaining walls of 50 blocks high is possible using the Bosun Robust Block.

Flat Surface

Image showing the distribution of forces once installed

Vertical pressure from above is displaced more evenly.


It is easy to pick up and handle on site. It is possible to carry six blocks with a gravity clamp.


The nib on the Robust block offers excellent horizontal shear resistance.

Other advantages of the nib are:

  • Less blocks are used in closed laying method.
  • Gaps between the blocks are smaller in the open laying method.
  • Less chance of soil falling through gaps in the open installation method.
  • It is possible to build steep walls at angles of up to 80 degrees.

Open back

Soil doesn’t leave the retaining structure when it erodes.

Installation guides

The Robust block offers installation guides on the top part of the block. These lines will ensure consistent overlapping of blocks on site.

Technical Information

Product NameRobust Retaining Wall Block
Length440mm without nib
Width256mm without nib (300mm with nib)
Mass± 47kg
Blocks per m2 (Closed face)9.09 blocks /m2
Blocks per m2 (Open face)5.13 blocks /m2