Thousands of security officers who work on hundreds of sites in Silicon Valley, including at Facebook, Cisco and Genentech, have unionized to push for higher wages and better benefits, SEIU United Service Workers West, a union that represents California workers, announced Saturday.

The 3,000 security officers are employed at G4S, Allied Universal, Cypress Private Security and Securitas, firms that provide security services on a contract basis to other businesses. The officers earn an hourly wage in the $12 to $20 range, not enough to live comfortably in the Bay Area, union officials said. Roughly 600 are located at Facebook and work for Allied Universal; others work at Google, Adobe and Qualcomm, among others.

“I like my job, but it doesn’t pay enough to take care of a family in the Silicon Valley,” said Jiovanny Martinez, a 29-year-old Allied Universal security officer who works at Facebook.

Martinez, who makes $18 an hour, said he lives in a three-bedroom home with eight other people in San Jose. He pays $600 a month — a portion of the house’s rent. Martinez, his wife and his two young daughters live in one of the bedrooms.

More service workers are pushing for higher wages and benefits. In 2015, unionized shuttle drivers transporting Facebook employees approved a contract that would raise their salaries from $18 to $24.50 an hour. That spurred other tech bus drivers to push for similar contracts.

Google, Apple and other companies have tried to bring their security staff in-house, which would provide more job stability. It is unclear how many security officers Google has employed in-house. The SEIU said some of the 3,000 security officers who joined the union do contract work at Google.

Google, Facebook and Qualcomm declined to comment. Apple, Genentech and Adobe did not respond to requests.

In 2015, Facebook said it would require its vendors to meet certain standards, including paying service workers at least $15 an hour and giving them at least 15 paid days off. If vendors do not offer paid parental leave, Facebook gives $4,000 bonus to parents for each new child.

Martinez said those vendor requirements did help workers, but more needs to be done.

“I would hope with higher pay, we will finally have our own place,” he said. He would like to see his pay go up to $27 an hour.

Some tech companies, including Cisco, are raising wages. In November, the company raised the wages of its vendors’ service workers at California facilities to at least $15 an hour.

Workers affected include security officers, landscapers and shipping clerks. The company said it “respects the rights of workers to organize.”

“Given the high cost of living in areas of California, we believe this is the right thing to do,” the company said of the wage raise. “We want to allow our vendors to pay their employees fairly for the important work they do.”

Cypress CEO Kes Narbutas said his security firm, along with others, signed a memorandum of understanding that they would not interfere with employees choosing to organize. That memorandum applies to Silicon Valley workers.

“We’re a responsible employer and responsible company,” Narbutas said. “We have had good relationships with SEIU for many years, and we kind of recognized that they can be effective in terms of representing our employees.”

G4S did not respond to a request for comment. Allied Universal said it respects its “employees’ legal right to choose to be part of a union.” Securitas declined to comment.

Wendy Lee is a San Francisco Chronicle staff writer. Email: wlee@sfchronicle.com Twitter: @thewendylee