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
harm to persons.