There may be created and constituted in every city, subject to the provisions of this act, a board of public works composed of 5 members, who shall be freeholders and electors of the city and shall serve without compensation. Such board shall, as near as may be, be non-partisan, no more than 3 members to be appointed from 1 political party, and shall be appointed by the mayor, by and with the consent of the council. One member shall be appointed for the term of 1 year, 1 member for the term of 2 years, 1 member for the term of 3 years, 1 member for the term of 4 years, and 1 member for the term of 5 years from the first Monday of May next thereafter, and on the 1st Monday of May of each year thereafter, 1 member shall be appointed for the term of 5 years, unless otherwise provided in this act: Provided, That it shall not be necessary for any city having a board of public works organized under the provisions of this act to reconstruct such board, but the existing board of public works shall continue unless abolished under the provisions of section 11 and 12 of this act.