A person, firm or corporation who is to install, construct, repair, alter and maintain an elevator shall secure from the director an elevator contractor license. The license shall be issued by the director, after his receipt of an acceptable application in writing and of the fee, to a person, firm or corporation found qualified to perform such work, and who is certified by the board as having successfully passed the examination given by the board. The application is not acceptable to the board until the applicant has shown by sworn affidavit that he or the person qualified for the applicant has had at least 5 years' experience as an elevator constructor or journeyman, or equivalent. A license shall expire on December 31 of the year in which it is issued.

     The contractor licensing requirements under this section for maintenance and repair work, as defined in this act, shall not apply to any firm, person, or corporation maintaining elevators in their leased or owned premises: Provided, That such elevators are not used by the general public, and that the work is performed by their permanent employees in accordance with approved procedures and practices.