Any person desiring to erect or increase the height of any structure, or permit the growth of any tree, or use their property, not in accordance with the regulations prescribed in this chapter, may apply to the Board of Adjustment, hereinafter provided for, for a variance from the regulations. The variances shall be allowed where it is duly found that a literal application or enforcement of the regulations would result in practical difficulty or unnecessary hardship and relief granted would not be contrary to the public interest but do substantial justice and be in accordance with the spirit of this chapter; provided any variance so allowed may be subject to any reasonable conditions that the Board of Adjustment may deem necessary to effectuate the purposes of this chapter.
(`86 Code, § 12.09)