Its quiet approach may be an acknowledgement that investors are wary of potentially risky Wall Street business and may mark down its shares, which currently trade at a premium to other big U.S. banks such as JPMorgan Chase & Co <JPM.N>.

"If I felt the bank were making a big investment banking push, they would need to do a good job of explaining why it has not made them riskier," said Thomas Russo, managing member at Gardner, Russo & Gardner, the bank's 43rd largest shareholder. "Otherwise, I would have to revisit the holdings."

Weiss said there was no cause for alarm.

"Our pace of growth is not so significant relative to the overall growth the bank has experienced that shareholders need be concerned that somehow we're growing some massive set of risks," he said.

Wells Fargo's largest shareholder, Warren Buffett - who has criticized the financial system's excessive use of derivatives - seems to be on board with the bank's plans. His Berkshire Hathaway Inc has increased its stake to 10 percent according to regulatory filings on Monday. Buffett declined to comment on whether he thinks the bank will become a riskier investment.

Old-School, New Building

Wells Fargo is still focused on its traditional business of lending to consumers and corporations and managing people's money.

Trading and investment banking accounted for just 4.6 percent of Wells Fargo's 2015 revenues, with part of the trading coming from outside the securities division, according to a spokeswoman.

That compares to about 26 percent for JPMorgan, counting only trading in its investment bank unit, according to its year-end earnings. Wells Fargo sees market share up for grabs as lenders such as Deutsche Bank AG <DBKGn.DE> and Barclays Plc <BARC.L> cut back their investment banking business in response to tough post-crisis regulations.

Buying offices in a 90-story, glass-and-steel tower overlooking New York's Hudson River - with a move-in scheduled for 2020 - is a symbolic move that shows the bank is intent on growing rather than making cuts like many Wall Street firms.