Each member of the board shall be a citizen of the United States and shall have been a resident of the state for at least five (5) years prior to the appointment. He shall be at least thirty-two (32) years of age, shall have been engaged in the practice of engineering or surveying, as the case may be, for at least ten (10) years and shall have been in responsible charge of important engineering or surveying work, as the case may be, for at least five (5) years. Each year of teaching engineering or surveying in a school or college shall be equivalent to a year of responsible charge of engineering or surveying work. Not more than two (2) members of the board at any time may be teachers of engineering in the universities or colleges of the state. All members of the board shall be licensed professional engineers or licensed professional surveyors, as the case may be.