“We anticipate moving into The Baird Family Hospital in early 2027,” he said.
“We are aware this exciting project has taken longer than the public and our staff would have liked to reach completion.
“But it is vital the building is as safe as possible and suitable, for years to come, for future generations.”
Mr Adam added: “Standards around hospital acquired infections and clinical practice are constantly evolving.
“It was important and right that we took time to weigh up new and emerging evidence as the build has progressed.”
BBC Scotland News has asked what the final cost of the project is expected to be.
Scottish Conservative North East MSP Tess White said she planned to raise the issue at First Minister’s Questions on Thursday.
“This latest setback is a devastating blow to patients who have been let down time and time again by repeated delays to the opening of the Baird Family Hospital,” she said.
A Scottish government spokesperson said:
“NHS Grampian is implementing several changes to the new hospital, resulting from a design review. This has impacted on the completion date and overall cost.
“These changes are subject to a commercial negotiation with the contractor and the Scottish government will continue to support NHS Grampian as they work through this process.”