CHICAGO—Plante Moran said Monday that it will combine its two downtown Chicago offices into its one of its locations at 10 South Riverside Plaza.

The accounting firm now operates out of the ninth floor at 10 South Riverside and 225 W. Washington Street. The latter office will be closed, the company said. The new lease will allow the firm to occupy office space on two floors of 10 South, as well as another 12,000 square feet on the ground floor, which will include street-level reception, space for meetings, conferences and training, and indoor and outdoor staff gathering areas.

Plante Moran now reportedly leases about 85,000 sq. ft. in both buildings, and will lease about that same amount at the 787,000-sq.-ft. 10 South. To allow for future growth, the company has the ability to lease additional space in the building. The company, based in Southfield, Mich., also has a suburban Chicago office in Elgin, Ill. The firm has 350 staff in Chicago and 70 in its northwest suburban office. The need to combine the offices results from Plante Moran's merger with Blackman Kallick in July 2012.

Steve Schneider, a managing partner at the firm, said the firm anticipates a spring 2014 completion date for the major renovation project. "We are very excited about our upcoming expansion and the consolidation of our two offices," Schneider said in a statement. "This new office demonstrates our commitment to Chicago and will enhance our client service capabilities while providing our people with an outstanding work environment."