The provisions of this division shall apply to all buildings constructed or under construction prior to October 6, 1933, or for which a building permit was issued prior to October 6, 1933, which on the effective date of this ordinance have unreinforced masonry bearing walls as defined herein.
EXCEPTION: This division shall not apply to detached one- or two-family dwellings and detached apartment houses containing less than 5 dwelling units and used solely for residential purposes.