It is vacating the Albert Kahn Building at 7430 Second Ave. as an unidentified buyer plans to convert it into 200 or so apartments plus first-floor restaurant space, said Alan Cobb, president of the firm.

"We are growing, hiring in all disciplines. We didn't want to be locked into the Albert Kahn Building that's being converted into residential," he said. "We are growing (our space) by about 10 percent. It will adequately handle the people we have now."

The 290,000-square-foot building is owned by a joint venture between Detroit-based The Platform LLC, New York City-based HFZ Capital Partners and New York City-based Rheal Capital Management, which is owned by Detroit native John Rhea. The Platform is run by Peter Cummings and Dietrich Knoer. The joint venture purchased the building along with the iconic 635,000-square-foot Fisher Building in 2015 for $12.2 million and had planned a large-scale redevelopment of the Kahn building.

"Peter and Dietrich made us an offer we couldn't refuse," he added.

The building, which has been the company's home since 1931, was put up for sale last summer.

"I've always wanted the office to be in the Fisher Building. Since I have been president, I really wanted this to happen," Cobb said.

About 100 employees will make the move; the firm employs a few dozen others in Brazil and Florida.

Albert Kahn Associates designed its new offices and Oak Park-based PCI Industries Inc. is the construction manager. Cobb declined to reveal the build-out cost.

Leasing has been ramping up in the Fisher Building in recent months.