The side yard regulations for dwellings are the same as those in the "B" multiple dwelling districts. In all other cases, a side yard is not required except:
A. On the side of a lot adjoining a dwelling district, in which case there shall be a side yard of not less than five feet; provided, however that if a side yard is provided where not required, it shall not be less than two and one-half feet in width;
B. On the street side of a corner lot that rears upon a dwelling district, in which case, there shall be a side yard of not less than five feet. (Prior code § 11-3-3 (e) (2))