In appeals to it, the Board of Zoning Appeals shall have authority to:
(a) Hear and decide any appeal where it is alleged that there is an error in any order, requirement or determination made by the Building Commissioner in the enforcement of this Business Maintenance Code.
(b) To allow or permit variations where there is practical difficulty or unnecessary hardship in the way of carrying out the strict letter of the provisions of this Business Maintenance Code, so long as the varying or modification of a requirement of this Business Maintenance Code will be in harmony with the general purpose and intent of the Business Maintenance Code, and the public health, safety and general welfare will be safeguarded and substantial justice done.