No building permit shall hereinafter be granted for the erection of a garage for more than four motor vehicles in a residential zone district. A garage shall be connected by an adequately surfaced driveway to the adjacent street, road or lane. The provisions of this section must be met on the single lot for which the garage, carport or approved shelter is accessory to the main use of the premises. These provisions shall not be deemed to limit commercial trucks or cars used upon a farm.