To limit the probability that the shape factor will not take into account the roof configuration affecting the maximum expected accumulation of snow on roof areas, which could lead to the excessive deformation of, or excessive stress in, structural elements, which could lead to damage to the building.
To limit the probability that the value of the shape factor used for roof areas will be less than 1.0 where not warranted, which could lead to the excessive deformation of, or excessive stress in, structural elements, which could lead to damage to the building.