Errors. The Board shall hear and decide appeals for variances as will not be contrary to the public interest where, owing to special conditions, a literal enforcement will result in practical difficulty or unnecessary hardship, so that the spirit and purposes of this chapter are observed and the public safety, welfare and justice secured. Applications for variances, other than applications for side yard or rear yard variances, shall be referred to the Plan Commission for review and recommendation prior to being acted on by the Zoning Board of Appeals.