The edition of the International Mechanical Code, currently or hereafter adopted and amended by the State Building Code Council and included in Title 51 of the Washington Administrative Code, is adopted as the Mechanical Code for the unincorporated areas of Pierce County; except that the amendments to the International Mechanical Code shall govern over the published provisions of the Mechanical Code. The effective date of subsequent editions of the International Mechanical Code in Pierce County shall coincide with the effective date of their adoption and amendment by the State Building Code.