In their interpretation and application, the provisions of this chapter shall be held to be the minimum requirements adopted for the promotion of the public health, morals and general welfare; for lessening the congestion in the street; for securing safety from fire, panic and other dangers; for the provision of adequate light and air; for preventing overcrowding of land or buildings; for the avoidance of undue concentration of population; and for facilitating adequate provision of transportation, water, sewage, schools, parking and other public improvements.