Facebook says it will invest $1 billion over the next decade to help fund 20,000 new homes in California, becoming the latest big employer to ramp up its financial commitment amid a crippling housing shortage.

Facebook’s plans follow a similar, unrelated $1 billion plan from Google that includes subsidies and land for market-rate and affordable homes. Other large Bay Area companies like Kaiser Permanente and Wells Fargo have also committed millions for housing as their employees struggle to afford the Bay Area and recruiting new workers to the area becomes increasingly challenging.

But despite billions pledged, most of it targeting the Bay Area, there are major challenges for the 40,000 homes envisioned by Facebook and Google as developers struggle with a glacial pace for approving new homes and rising construction costs.

Facebook’s effort comes weeks after CEO Mark Zuckerberg said the Bay Area’s high home prices and transit woes were pushing the company to grow faster in other regions, underscoring the company’s business incentives in funding more homes. The social media giant has already expanded throughout the Bay Area, with new offices planned or open in Burlingame, Fremont, Mountain View, San Francisco and Sunnyvale. It has 40,000 employees globally and about half work in the Bay Area.

“$1 billion is a big deal anyway you slice it. It is absolutely encouraging Facebook is following suit behind Google and others,” said Ben Metcalf, former director of the state’s Department of Housing and Community Development and principal of consulting firm Stronger Foundations LLC. “It’s just not clear if it will be transformational or not, (but) it has the potential.”

Matt Franklin, CEO of MidPen Housing Corp., an affordable housing developer, said, “The housing affordability challenge is a complex one.”

He said that Facebook’s plan is encouraging, but without more specific details on locations and funding mechanisms, “it’s hard to evaluate the impact.”

While few details on timeline, funding and location were shared, Facebook said the funds will be used in five areas:

• $250 million will fund a partnership with the state to build mixed-income housing on excess public land.

• $150 million will be invested in the Partnership for the Bay’s Future, which has an existing housing fund. The Partnership is a group of nonprofits and companies that are working on affordable housing policy and projects.

• $225 million worth of land near its Menlo Park headquarters will hold 1,735 homes that are proposed.

Employers’ plans for big problem Kaiser Permanente: Committed $200 million to grow affordable housing and fight homelessness in Bay Area cities and other places where it operates. Partnership for the Bay’s Future: A group including Facebook and the Chan Zuckerberg Initiative is raising $540 million for affordable housing, with $150 million newly committed by Facebook. Google: Putting $1 billion to work on addressing the region’s housing shortage, including rezoning land it owns. So far, it ’s invested $50 million to Housing Trust Silicon Valley’s TECH Fund to help finance 181 affordable homes in two San Jose projects. Wells Fargo: Pledged $1 billion in donations through 2025. Marc and Lynne Benioff: The Salesforce co-CEO and his wife donated tens of millions of dollars to fund research on homelessness and subsidize rents for the newly housed.

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• A $25 million investment will be used to build 90 to 120 homes for teachers and school employees on public land in San Mateo and Santa Clara counties.

• $350 million will be used for additional programs, potentially including housing in other areas where Facebook has offices.

With construction costs in the Bay Area soaring to more than $700,000 per housing unit in many projects, Facebook and its partners could need more than $10 billion in additional funding to complete 20,000 new homes. The state is short millions of homes and experts say it will take decades to make a dent in the crisis. The region’s lengthy, complex and expensive approvals process will continue to make housing hard to build, even with additional funding.

“We can’t work incrementally,” said Doug Shoemaker, president of Mercy Housing, a nonprofit developer working on the Silicon Valley teacher housing project funded in part by Facebook. “If we’re going to address this, we’re going to have to do something radically different than what we’re seeing today.”

Facebook’s $25 million, along with free land and $6 million from Santa Clara County and $3 million from Palo Alto, made the teacher housing project feasible. “That’s an incredible gift” and an example of a new level of involvement from a tech company, Shoemaker said.

Gov. Gavin Newsom expressed delight Tuesday at Facebook’s planned $250 million partnership with the state on mixed-income housing.

“They should be applauded,” he said. “Facebook didn’t have to do this, but they did the right thing.”

The governor said he hoped the Facebook contribution persuades other companies to get involved. Six cities have been identified as places where housing can be built on surplus state property, he said, with Stockton the likely starting point on Caltrans sites.

Some of the earliest construction is likely to be modular and prefabricated housing, to provide shelter as quickly as possible, Newsom said.

Even Facebook’s plan for housing on its own land faces considerable hurdles. Facebook’s Menlo Park project, Willow Village, calls for 1,735 units and 15% affordable housing on land it owns near its headquarters. It was proposed more than two years ago, but may not be up for approvals until 2021. It isn’t clear if Facebook plans to donate the land, lease it to developers or build the housing itself. Facebook didn’t immediately respond to requests for more information, but confirmed that the housing wouldn’t be reserved for its employees.

Facebook’s $150 million investment in the Partnership for the Bay’s Future brings the fund to its $500 million goal, according to manager Local Initiatives Support Corp. Facebook is investing the money — not donating it — and could get a return on this fund.

The next biggest investors in the fund are Morgan Stanley with $100 million, Kaiser Permanente at $40 million, and Mark Zuckerberg and Priscilla Chan’s Chan Zuckerberg Initiative at $40 million. The fund aims to preserve and produce 8,000 Bay Area housing units over the next five to 10 years.

The fund’s first project is small: helping to build eight new homes affiliated with a Berkeley church. But the project will kick off more partnerships with faith-based organizations and additional, larger projects will be announced soon, said Judith Bell, vice president of programs at the San Francisco Foundation, which is the administrator of the fund.

Bell said bringing together the private sector, government and philanthropic groups can make a dent in the housing crisis. The Partnership for the Bay’s Future has a separate policy fund that’s raised $21 million, including $1 million from Facebook, to advocate for more renter protections and loosening housing development restrictions.

“The crisis is so deep and so wide, there’s no silver bullet,” Bell said. “But if we move all these different components, we can make a difference.”

Editor’s note: This story has been updated to clarify Google’s contribution toward housing in San Jose.

Chronicle staff writer John Wildermuth contributed to this report.

Roland Li is a San Francisco Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf