Sec. 5. CERTIFICATE OF NONAPPLICABILITY OF STATUTE. Except in cases excluded by Section 8 of this Act, every person about to apply to the City of Galveston for a permit to construct any structure in the Old Galveston Quarter or to reconstruct, alter or demolish any structure now or hereafter in said Quarter shall deposit with the secretary of the Commission his application for such permit together with all plans and specifications for the work involved. Within fifteen (15) days thereafter, Saturdays, Sundays and legal holidays excluded, the Commission shall consider such application, plans and specifications and determine whether any exterior architectural feature is involved. If the Commission determines that no exterior architectural feature is involved, it shall cause its secretary to endorse on the application forthwith a certificate of such determination and return the application, plans and specifications to the applicant.