Important notice:

These design tables are intended to assist in estimating the cost of proposed gravity retaining walls to be built with Terraforce blocks and to confirm the viability of such undertaking. Your local engineer will be able to either verify the table creator values or will be able to produce a more accurate cross section. The table creator does not eliminate the need to seek the advice of a competent person who understands the principles of retaining wall design. 

For a reasonable fee, Terrasafe Designs can assist in providing a pertinent design. We can also arrange for a quotation by an experienced installer or for supervision by an engineering professional in some areas.  For the design of composite Terraforce walls, i.e., structures with mechanically stabilised backfill or with additional stability requirements, - double block rows, cement stabilised backfill or reinforced concrete infill, etc., please go to Maxiwall Pro - Terraforce design software or contact Terrasafe Designs.   

Minimum CRB block wall requirements & quality assurance during manufacture. 

The production of Terraforce concrete retaining blocks must adhere to local and international standards. The blocks have been extensively laboratory tested, locally and internationally and have been evaluated by reputable accreditations agencies. 

Our minimum standard is mostly based on the following codes. 

SANS 207: 2011 and SANS 508/2006   

• CMA manuals  
• BS 8806  
• ASTM-D6916-18 and ASTM-C 90-99 
• ICB 1802 and ICB 1805.4.1 + 2 

Licensed manufacturers must adhere to our minimum standard and regular compressive strength tests must be conducted. Weight and dimensional tolerances must be complied with as part of our quality assurance programme. 

A word of caution:

Avoid disappointment and take note of these possible shortfalls. 

• Insufficient constructed mass – no or negligible design input or use of incorrect block size/infill material. Incorrectly conveyed site information or poor drawings/specifications. Appoint a competent designer with experience and Professional Indemnity Insurance cover.

• Saturated backfill – lack of storm water control above the wall. Inadequate sub-soil drainage.
   
• Design angle and height exceeded – lack of supervision during construction. Unauthorised changes to the wall details.
   
• Settlement of backfill – substandard material, inadequate compaction or backfill erosion. Lack of supervision during placement of backfill.
   
• Undermining – excavation close to wall foundations.
   
• Excessive loading above the wall – not accounted for in the original design.
   
• Limited bearing capacity – poor or saturated founding conditions or no foundation at all.
   
• Incorrect selection of supplementary reinforcement – poor connection between blocks and geo-grid or choice of inadequate geo-grid. Inadequate concrete or reinforced concrete infill, alternatively cement stabilised backfill.
   
• Linear cracking of blocks – excessive lateral earth pressure or poor quality of blocks.
   
• Non-adherence to local OHS Act – (Occupational Health and Safety Act). 

Disclaimer: 

Although every reasonable effort has been made to ensure that the technical information and the design procedure presented in this guide are correct, neither Terraforce CC. and any supplier of the product, nor their consultants, who have contributed to the preparation of these guidelines, will be held liable for any loss or damage, either direct or consequential, arising from any failure of installations constructed with Terraforce precast concrete blocks.  

As with any structure, the design of Terraforce projects should only be undertaken by suitably qualified and experienced designers with due cognisance being taken of the specific geotechnical conditions and vital soil parameters pertaining to the site.