No person shall engage in the business of roofing or repairing, recoating, altering or changing roofs of buildings or other structures, whether or not under construction, in the city, with tile, slate, sheet metal, mastic and gravel roofing, ready roofing, over-shingles, asphalt or asphalt shingle roofing, felt composition roofing or any other kind of prepared roofing, without first obtaining a license therefor.