To limit the probability that moisture-content-related
soil movement or the weathering of pyritic material will lead to the
heaving or subsidence of floors-on-ground, which could lead to:
the failure of floors-on-ground, or
the compromised structural integrity of floors-on-ground,
which could lead to the ingress of moisture from the ground, which
could lead to the deterioration of building elements.
This is to limit the probability of
damage to the building.