If a building which is to be used for industry is to be built adjacent to a residence or a lot located in a residential area, the front and side yard dimensions will be a minimum of 50 feet, with the first 20 feet made up of lawn, shrubbery and evergreen trees to form a continuous natural screen. The same will apply to the rear yard dimensions when it is adjacent to a residence or lot in a residential district. If any part of the residence or residential area is being used as a business, the side and rear yard dimensions necessary for the above-mentioned building will not be less than 15 feet.