Sisk will provide property investment firms Moorevale and Rockspring with high quality commercial office space at the site.
The 48-week refurbishment and fit out programme will also include construction of a two-floor extension enlarging the building to 85,000 sq. ft.
Charlie Bishop, Director at Moorevale, said: “This asset is located in a sought after location in the City of London and on completion of the rejuvenation works will provide premium office space.
“We were impressed by John Sisk & Son’s innovative approach to the base design and, with a proven track record of delivering quality commercial projects on a tight timescale, we are confident the solutions they offer will add value to the investment.”
Peter Glass, Regional Director at John Sisk & Son, added: “Our strategy for 63 St Mary Axe is to ensure the earliest delivery of the project, focusing our solutions on increasing their potential to maximise rental revenue.
“We have extensive experience working on large commercial spaces in demanding city locations.”