(a) Continuation of existing use. The legal use and occupancy of any structure existing on the effective date of this chapter or for which it had been heretofore approved, may be continued without change, except as may be specifically required herein or as may be deemed necessary by the director for the general safety and welfare of the occupants and the public.
(b) Change in use. It shall be unlawful to make any change in the use or occupancy of any structure which would subject it to any special provision of this chapter without approval of the director and his certification that such structure meets the intent of the provisions of law governing building construction for the proposed new use and occupancy and that such change does not result in any greater hazard to public safety or welfare. (1975 L.M.C., ch. 1, § 1.)