Investigators from the San Mateo County District Attorney's Office and the Menlo Park and Belmont police departments conducted the operations Thursday and Friday, according to the district attorney's office.
Suspected unlicensed contractors who had advertised in newspapers or on the Internet, or who had been the focus of previous consumer complaints, were contacted and asked to bid on projects such as plumbing, landscaping, roofing, painting or fencing.
Unlicensed contractors who bid more than $500 for a job were arrested or cited for misdemeanor charges of contracting without a license, the district attorney's office reported. Penalties for conviction range up to six months in jail and a $1,000 fine.
State law requires anyone who takes on home improvement jobs valued at $500 or more to have a license issued by the Contractor's State License Board, according to the District Attorney's Office.
Authorities warned that unlicensed contractors could pose a risk to consumers through inferior workmanship, not completing jobs, or by employing workers without liability insurance, which could result in lawsuits against homeowners if a worker is injured on the job.
Homeowners are advised to verify a contractor's license by calling the CSLB at (800) 321-2752 or visiting www.cslb.ca.gov.
They are also advised to be wary of those offering contracting services door to door, to check references, not to pay in cash or pay more than 10 percent down on work, and to contact the CSLB with any complaints.