Section 12. Zoning ordinances or by-laws shall provide for a zoning board of appeals, according to the provisions of this section, unless otherwise provided by charter. The mayor subject to confirmation of the city council, or board of selectmen shall appoint members of the board of appeals within three months of the adoption of the ordinance or by-law. Pending appointment of the members of the board of appeals, the city council or board of selectmen shall act as the board of appeals. Any board of appeals established hereunder shall consist of three or five members who, unless otherwise provided by charter, shall be appointed by the mayor, subject to the confirmation by the city council, or by the selectmen, for terms of such length and so arranged that the term of one member shall expire each year. Each zoning board of appeals shall elect annually a chairman from its own number and a clerk, and may, subject to appropriation, employ experts and clerical and other assistants. Any member may be removed for cause by the appointing authority upon written charges and after a public hearing. Vacancies shall be filled for unexpired terms in the same manner as in the case of original appointments. Zoning ordinances or by-laws may provide for the appointments in like manner of associate members of the board of appeals; and if provision for associate members has been made the chairman of the board may designate any such associate member to sit on the board in case of absence, inability to act or conflict of interest on the part of any member thereof, or in the event of a vacancy on the board until said vacancy is filled in the manner provided in this section.

The board of appeals shall adopt rules, not inconsistent with the provisions of the zoning ordinance or by-law for the conduct of its business and for purposes of this chapter and shall file a copy of said rules with the city or town clerk. In the event that a board of appeals has appointed a zoning administrator in accordance with section thirteen said rules shall set forth the fact of such appointment, the identity of the persons from time to time appointed to such position, the powers and duties delegated to such individual and any limitations thereon.