No building hereafter enlarged, extended or so altered,
wholly or in part, as to change its classification as a residential,
business or industrial building, and no building hereafter altered
for which a certificate of occupancy had not been issued heretofore,
shall be occupied or used, in whole or in part, until a certificate
of occupancy shall have been issued by the Building Commissioner certifying
both that the work for which the permit was issued has been completed
substantially in accordance with the permit and the provisions of
law applying to such an alteration, and that the building is safe
for occupancy insofar as can be determined by visual inspection, provided
that if the occupancy or use of such building was not discontinued
during the work of alterations, the occupancy or use of the building
shall not continue for more than 30 days after completion of the alteration
unless such certificate shall have been issued.
