Where strict application of any of the requirements of this chapter, such as in the case of exceptionally irregular, narrow, shallow or steep lots or other exceptional physical conditions, would result in practical difficulty or unnecessary hardship that would deprive the owner of the reasonable use of his or her land or building, but in no other case, the Zoning Board of Appeals shall have the power, in passing upon appeals, to grant a variance to any of the regulations or provisions of this chapter relating to the area, bulk, construction or alteration of buildings, signs or structures or the use of land and buildings so that the spirit of this chapter shall be observed, public health, safety and welfare secured and substantial justice done.