If a city decides not to adopt a certain published amendment, and amendments to building codes are not adopted administratively by the building official, it must reject the amendment by at least a two-thirds vote of the total membership of the governing body.  This must be done every time a new amendment is published to the code. Each amendment rejected must be identified by "date and source."  The ICC and other organizations, when publishing building codes or amendments, specify the date of the code or amendment by year, e.g. "2012 edition with 2014 revisions." The "source" is the particular code being adopted.
The statute does not specify that rejection of amendments must be by written instrument. However, a written resolution is an effective way to keep a record of the votes on each amendment considered and what action was taken on each. See Sample 3, "Resolution rejecting specific amendments to building codes." If the rejection is not by written instrument, the meeting minutes should contain an accurate reference to the specific amendment considered and either a roll call vote or a notation that the vote to reject was effected by at least a two-thirds majority of the total membership of the board.
 T.C.A. § 6-54-502(b).