All members of the board, except the public members, shall be contractors actively engaged in the contracting business, have been so engaged for a period of not less than five years preceding the date of their appointment and shall so continue in the contracting business during the term of their office. No one, except a public member, shall be eligible for appointment who does not at the time hold an unexpired license to operate as a contractor.

The public members shall not be licentiates of the board.