To limit the probability of an inadequate physical bond between the first and second coats of stucco, which could lead to stucco being of inadequate strength to resist gravity, lateral or impact loads, which could lead to delamination.
Where stucco is applied to masonry chimneys, this is to limit the probability of precipitation or meltwater ingress, which could lead to the premature failure of chimney liners, which could lead to the leakage of carbon monoxide gas into living space, which could lead to the acute poisoning or asphyxiation of persons.