The building at 55 Colmore Row, formerly home to law firm Wragge Lawrence Graham & Co, is getting three extra floors added on top to create 160,000 sq ft of grade A office space.
The listed 19th Century banking hall will form a central part of the redevelopment and will be reconfigured as a reception. The rear of the building on Barwick Street will be replaced with a full-height glazed façade.
Completion is scheduled for autumn 2016.
Client for the project is IM Properties. The scheme has been designed by AHR Architects, while DBK is quantity surveyor on the project and Projex Building Solutions is project manager.
Morgan Sindall managing director Dave Smith said: "Anyone who has worked in or around Birmingham will be aware of 55 Colmore Row. They may be less familiar, however, with the volume of work that will need to be undertaken to give the building a new lease of life.
"The complexity of adding new floors to the top of the building, combined with the time-scale in which we are working means that there is significant planning required to ensure we deliver.
"It is a fantastic and high-profile project to be involved with and I am confident that we will deliver to exactly the standard that IM Properties is seeking for 55 Colmore Row."