ROCHESTER — Mayo Clinic is kicking off a five-year, $217 million expansion of its St. Marys Hospital campus in Rochester.

The plan, announced by Mayo officials last week, includes adding three floors to the Generose Building, moving and upgrading the cardiac surgery facilities and expanding the Neonatal Intensive Care and Pediatric Intensive Care units.

Dr. Bob Cima, Mayo Clinic’s medical director of hospital operations, said the strategic plan has evolved over the past five years.

“We looked at where the needs were most pressing,” Cima said. “We decided that to do this in an incremental fashion with one little project here and there was not the most efficient way of doing this.”

Much of the project is about modernizing the historic St. Marys campus and finding creative ways to expand the landlocked space.

“This project not only demonstrates Mayo Clinic’s commitment to our mission, but also our commitment to the future growth of Rochester,” Mayo CEO Dr. John Noseworthy said in the announcement.

The most visually dramatic piece of the multi-year project is building three more floors on top of the five-story, 24-year-old Generose Building. Adding three floors will add 150,000 square feet to the building. About half of that space is expected to house Mayo Clinic’s consolidated Physical Medicine and Rehabilitation Hospital, now based in the nearby Mary Brigh building.

Other changes at St. Marys will expand the number of private patient rooms and reducing the number of semiprivate rooms. The campus has 184 semiprivate rooms, 150 general care beds and 34 intensive care beds.

Construction on the first pieces of the project is expected to begin within a few months.