Accessory buildings and facilities. In any district wherein a rear yard is required, an accessory building or facility may be located in such rear yard no closer to the rear lot line than a distance equal to 10% of the lot width, but in no case less than five feet, and no closer to the side lot line than would be permitted for the main building side yard width. If the accessory building is connected to the principal building by a breezeway or other covered connecting building, the accessory building shall be considered part of the principal building.