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Robust Block

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.

Why is it important to have blocks of consistent heights?

  • The layer on top of irregular blocks will rock back and forth.
  • There will be uneven weight distribution of blocks placed on top of an uneven layer leading to stress points and ultimately block failure.
  • Geotextiles placed between uneven rows of blocks might tear or rip out.
  • It wastes a lot of time to level blocks on site with little stones etc.


Technical Information

Product NameRobust 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

Basic colour options for this product:

Other colours could be available on request.

Consult your local representative for more information on other colour options.
*T’s & C’s may apply.

See our colour chart for other colour options.

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Robust Block with special V shaped stiffeners

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.

Additional Information

Flat Surface

Robust Block Weight Distribution

Vertical pressure from above is displaced more evenly.


Robust Block Nib

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

Open back

Robust Block with Soil eroding from the back

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


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

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.

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.

Contact Us

Head Office
Cnr Cresset and Musket Roads
Midrand Industrial Park
Phone: 011 310 1176
Email: info@bosun.co.za