The Nuclear Decommissioning Authority has appointed Morgan Sindall to build an £18m office in Whitehaven's Albion Square.
Two four-storey office buildings, totalling 100,000 sq ft, will be constructed at two neighbouring sites in Swingpump Lane in the centre of the town. The offices will house 1,000 Sellafield office workers who will move from the Sellafield site.
RMJM acted as concept and design architects, Hurd Rolland Partnership as project architects with project management by Drivers Jonas Deloitte.
John Clarke, chief executive of the NDA, said: "Albion Square is an excellent example of how we can work with colleagues at Britain's Energy Coast, Copeland Council and the supply chain to deliver a project that not only enables Sellafield to relocate staff giving us greater flexibility to deliver decommissioning on site, but also will bring real economic benefits to Whitehaven itself."