Free standing walls should not exceed the 2:1 ratio
Walls less than the 2:1 ratio need internal supports to prevent collapse
Std retaining walls should not exceed the 2:1 ratio
Retaining walls with additional loads on top of them, e.g. driveways, banks, buildings, will require extra thickness, and possibly an engineer's design.
Gabion support posts must extend to at least 1.5 x Depth from the top of the gabion basket
Gabion support posts spacing should be no greater than 1.0m apart.
Hollow steel posts need to be capped to prevent water entry
Gabion support posts need to strong enough that they do not snap or bend under the load of the gabion wall.
An engineer's design will take precedence, over these guidelines.