High rents send firms 'over the edge' in Beijing, Shanghai

At the same time, Beijing's and Shanghai's non-core business districts have higher vacancy rates and building owners are more than willing to offer discounts to premium clients.

As multinationals expand in China, they also find it necessary to put their back-office business, such as research and development, logistics and data management, in suburban areas. For example, banks may prefer to put their headquarters in Beijing's Financial Street, near major regulators and other financial institutions. But they might find it attractive to locate their call centers in suburban areas.

As more corporations move to non-core submarkets, rents there will also rise.

Zhang Ping, director of C&W's Beijing research operations, drew a comparison between Hong Kong and the first-tier cities on the mainland.

Five years ago, major corporations in Hong Kong started their retreat from the Central business district, which has the most expensive office space in the world. Kowloon, on the other side of the harbor, became a popular alternative. The result was an upswing of rents in Kowloon, while rents in Central declined 16.8 percent year-on-year in 2012.

"Rents in Beijing's CBD are unlikely to see such a drop in coming years. But rents in non-core areas will certainly rise," said Zhang.

However, Andy Zhang, managing director of C&W China, warned that moving to a suburb is not a one-size-fits-all solution.

When corporate executives consider the option of moving, they should think of whether a new office location would affect their current business operations, Zhang said.