(2) Subsection (1) of this section is operative:
(a) With regard to the state structural code, July 1, 1974.
(b) With regard to the state mechanical, heating and ventilating code, on the effective date of such code as determined under ORS 183.355.
(c) With regard to each specialty code not named by paragraphs (a) and (b) of this subsection, on the effective date, as determined under ORS 183.355, of the first amendments to such code adopted pursuant to this chapter. [Formerly 456.775]