Generally, a contractor's license is required for any new construction, structural additions, roofing, gas piping, plumbing, electrical/alarm work, pool/spa work or any job which requires a building permit.
Beware of Construction Con Artists, Who May:
Target the elderly, uninformed or the young and inexperienced.
Focus on roofing and remodeling.
Solicit door-to-door, claiming to have "just finished a job down the street."
Arrive in unmarked vans or trucks, possibly from out-of-state.
Use a post office box address with no street address.
Promise to use your home as a demonstration model at a bargain price.
Offer to work for you, only if you obtain the necessary building permits, which makes you responsible for the work done.
Ask for all the money up front.
Become injured on your property and sue you for damages.
(Excerpted from "Protect Your Home: Hire Only Licensed Contractors" from the Department of Business and Professional Regulation (DBPR) published Feb 28, 2003.)