To limit the probability of insufficiently thick concrete footings, which could lead to:
This is to limit the probability of weak concrete, which could lead to shear failure under gravity loads transmitted through foundation elements, which could lead to excessive settlement of the soil and structural damage to the foundation and the building.
This is to limit the probability of:
For floors and elements supporting floors, this is to limit the probability of excessive deflection, which could lead to rough or uneven walking surfaces, which could lead to persons tripping or falling, which could lead to harm to persons.