The council is relocating from its current premises at County Hall in Oxford which will be sold off to fund the big office upgrade project at Speedwell Street.
These Speedwell offices have for many years provided city centre accommodation for the council in addition to County Hall.
Willmott Dixon will extend with extra floors and redevelop Speedwell House to create a 5,200m2 ‘net zero in operation’ office.
Work is hoped to commence in the middle of 2025, using sustainable technologies including air source heat pumps.
Concept designs of Speedwell House include a new Council Chamber and Coroner’s Court in a building that is modern, fit for purpose and accessible.
Councillor Dan Levy, Oxfordshire County Council’s cabinet member for finance, added: “This is a once in a lifetime opportunity for us not only to create a modern carbon-neutral office.
“We’re looking forward to seeing the new offices take shape and to moving in during early 2027.”
Richard Poulter, managing director for Willmott Dixon in the South said: “We recently completed a series of decarbonisation projects for Oxford City Council at four leisure centres: Ferry Leisure Centre, Leys Pool and Leisure Centre, Barton Leisure Centre, and Hinksey Outdoor Pool. We’ll be taking the skills and learning from here to Speedwell House.”