The notice and order, and any amended or supplemental notice and order, shall be served upon the record owner and posted on the property; and one copy thereof shall be served on each of the following if known to the department head or disclosed from official public records: the holder of any mortgage or deed of trust or other lien or encumbrance of record; the owner or holder of any lease of record; and the holder of any other estate or legal interest of record in or to the building or the land on which it is located. The failure of the department head to serve any person required herein to be served shall not invalidate any proceedings hereunder as to any other person duly served or relieve any such person from any duty or obligation imposed by the provisions of this section. (Prior code § 61.05.504)