SAN JOSE -- A three-day sting this week targeting unlicensed home-improvement contractors netted 19 suspects in the South Bay and 121 throughout the state, according to state licensing officials.

Investigators with the Contractors State License Board looked for offenders advertising on fliers, in phone directories, online, on posted business cards and "penny saver" periodicals, said spokeswoman Melanie Bedwell.

Often, it was as simple as finding an ad that doesn't include the contractor's license number.

"If they're not licensed they may not know that's required by law," Bedwell said.

The 19 suspects from the South Bay plied trades such as painting, drywall, concrete work, fencing, landscaping and tree trimming. All were given a notice to appear in court for contracting without a license, and nearly all for illegal advertising.

Most of the suspects hailed from San Jose, with exceptions being from Campbell, Saratoga, San Carlos, East Palo Alto and Newark. Other sting areas ranged from Yolo County in the north to San Diego County in the south.

By law, a license is not required if the job is valued at less than $500, but Bedwell said oftentimes that is exploited.

"What they end up doing is going over to fix a sprinkler for $50, but they say 'Oh I can also do this, and I can do that' and it adds up," she said. "You have to look at the comprehensive job. It's federal law that you can't break those things up."

The penalty for contracting without a license is up to six months in jail and a fine of up to $5,000. For false advertising, it's a fine of $700 to $1,000.

For the sting, investigators posed as homeowners seeking bids for various home improvement projects.

The contractors board said it's critical that people make sure contractors are licensed, bonded and insured for their own protection.

"If someone is unlicensed and they don't do the work or it's substandard, you have to start over again, do the job twice," Bedwell said. "The building permits can be pulled. You can have a patio built, but then have it torn down because it didn't meet code."

Contractors licenses can be checked by visiting www.cslb.ca.gov or calling 800-321-2757.

Contact Eric Kurhi at 408-920-5852. Follow him at Twitter.com/erickurhi.