(a) A board of adjustment is established, which shall consist of five members and two alternate members appointed by the city council.

(b) Members and alternate members of the board of adjustment shall have been residents of the city for at least one year prior to their appointment. Members and alternate members shall be registered voters.

(c) Members of the board of adjustment shall be appointed for staggered terms of three years. In addition, the chairman of the planning and zoning board or his duly authorized representative shall be an ex-officio member of the board of adjustment.