To authorize, upon appeal in specific cases, such variance from the terms of this chapter as will not be contrary to the public interest where, owing to exceptional and extraordinary circumstances, there are practical difficulties or unnecessary hardships in the way of carrying out the strict letter of this chapter, subject to terms and conditions to be fixed by the Board of Appeals; provided, however, that no such variance shall be granted unless said Board finds that:
(a) There are physical conditions, such as in the case of an exceptionally irregular, narrow, shallow or steep lot, fully described in the findings of said Board, applying to the land or building for which the variance is sought, which conditions are peculiar to such land or building and have not resulted from any act of the applicant or any prior owner.
(b) For reasons fully set forth in the findings of said Board, the aforesaid circumstances or conditions are such that the strict application of the provisions of this chapter would deprive the applicant of the reasonable use of such land or building, and the granting of the variance is necessary for the reasonable use of the land or building, and the variance as granted by said Board is the minimum variance that will accomplish this purpose.
(c) The granting of the variance under such conditions as said Board may deem necessary or desirable to apply thereto will be in harmony with the general purpose and intent of this chapter, will not represent a radical departure therefrom, will not be injurious to the neighborhood, will not change the character thereof and will not be otherwise detrimental to the public welfare.