In a Class I Residential, Class II Residential or Class III Residential District, except where within an Unrestricted Area District, each dwelling and each apartment house shall be deemed a separate building. For every building erected, there shall be a side yard along each lot line other than a front line or a rear line, except that in a Class III Residential District any number of residences may be built as a continuous structure and be considered as a single building for the purpose of this section. At least twenty percent of the width of each lot shall be devoted to side yards, provided that not more than sixteen feet need be so devoted. The least dimension of a side yard shall not be less than five feet. However, in the case of any building more than two and one-half stories in height, such least dimension shall not be less than one-sixth of the height of the building. Any dwelling house existing on June 6, 1949, and having side yards that do not comply with the provisions of this section may be extended along such existing side yard lines.
(1956 Code Sec. 1319.04)