California - Workers roam with laptops, meet on sofas and scribble on walls at Facebook Inc's new Silicon Valley headquarters, where rusted steel beams, exposed heating ducts and plywood-covered corridors are part of the decor.

The office campus in Menlo Park, California, was renovated for US$250 million (S$323.8 million) in a 'hacker' style intended to express the culture of the world's largest social-networking company.

'We wanted to keep honest, industrial materials and give the place its own eclectic look,' said Mr Everett Katigbak, the Facebook designer overseeing the facility, as he showed off the first of 10 structures to be occupied at the 1 million sqft complex. About 2,000 workers relocated from the company's former base, in nearby Palo Alto, last week.

Some of technology's biggest companies are moving into non-traditional properties.

Google Inc's New York base is a warehouse in Eighth Avenue in Midtown South, bought by the company last year for US$1.8 billion.

Online gaming company Zynga Inc, which raised US$1 billion in an initial public offering last week, this year took more than half of a former wholesale fashion mart in San Francisco.

Age and exterior appearance are less important than interiors that can be reconfigured as 'funky space that young people want', said Mr John Guinee, an analyst who follows real-estate investment trusts for Stifel Nicolaus & Co in Baltimore.

'Real-estate developers think tenants want architecturally significant space on the outside, but they really want cool space on the inside, access to public transportation and open-space planning,' he added.

Open areas, rather than cubicles, encourage 'cross-pollination' favoured by tech, media and 'knowledge-based' firms, said Mr Chris Caton, a Reit analyst at Morgan Stanley in San Francisco.

Such 'cool spaces' will spread to US cities outside major Internet hubs as tech-savvy workers across industries spend more time at work and conduct their lives from hand-held devices, said Mr Peter Rummell, a developer in Jacksonville, Florida.

At Facebook's new campus, the office buildings are arranged along a narrow interior courtyard with storefronts featuring food, medical, cleaning and other services for employees, all of them free, said company spokesman Slater Tow.

The complex has internal atriums to increase natural light, rows of white benches topped by 61cm monitors and items brought in by employees, including a tiki bar, Charlie Sheen poster and Sarah Palin bobble-head.

The lively atmosphere may be needed because the campus, considered state-of- the-art when occupied by Sun Microsystems, sits in relative isolation between an expressway and San Francisco Bay salt ponds. Some people used to call it 'Sun Quentin', after the state prison at San Quentin, about 80km north, said MrGregory Davies, a vice-president at brokerage Cassidy Turley in San Jose, California. 'It was way out there on the water, a big old thing that nobody was using.'

That was then. As of yesterday, Facebook hopes its sprawling tech hub in Willow Road will be 'cool space' again. It's been rechristened 10 Hacker Way.