Side yard. There shall be a side yard along each lot line with a width of not less than 15 feet; except that, in case of a dwelling erected without a garage, one side yard shall be not less than 27 feet wide, and except that, in all cases (other than corner lots) the total combined width of both side yards shall be not less than 35 feet. In the case of corner lots, the side yard opposite the principal front yard shall be not less than 30 feet wide and the other not less than 15 feet wide, except that, in the case of a dwelling erected without a garage, the lesser side yard shall be not less than 27 feet wide. Where the planes of all walls of a building facing a side lot line intersect such line at a minimum angle of 25° or more, the lesser-required setback distance may be reduced by five feet, except in the case of a building erected without a garage.