In this guide
5. Walls below ground level
Depending on whether the foundation has been cast as deep-fill or shallow-fill, there could be a small or large amount of wall construction needed below ground level (substructure), on which the above ground walls (superstructure) will be built.
The principal requirement of the substructure is to ensure adequate support is provided to the superstructure. To remain effective the bricks or blocks and mortar should be resistant to frost and also to sulphates within the ground.