Rising risks, including an eventual increase in interest rates, are leading commercial-property investors to borrow less and expect lower returns, said real estate executives including Rob Speyer and Richard J. Mack.

AREA Property Partners LP isn’t building U.S. offices without signed tenants, even as commercial values increase, Mack, chief executive officer for North America, said at the Bloomberg Commercial Real Estate Conference today in New York. Tishman Speyer Properties LP has used “average leverage” of less than 50 percent in deals since 2010, said Speyer, the New York-based office developer’s co-chief executive officer.