Building work on 850 homes at the Hounslow Civic Centre site is due to begin next summer after a developer was appointed.
Hounslow Council's existing HQ will be demolished, with staff moving to a new building at the car park site opposite Yates' pub in Bath Road, just off Hounslow High Street.
At a meeting on Tuesday (July 7), cabinet members agreed to appoint BY Development, a consortium of Bouygues Development, Notting Hill Housing and Redrow Homes, to create 850 homes at the current Civic Centre site in Lampton Road.
Work on the first 190 of those homes, where the register office currently stands, is due to begin in July next year, with births, deaths and marriages to be recorded at Feltham Lodge.
Those homes are scheduled to be completed in March 2018 to ensure the council meets the conditions of an £18.5m Greater London Authority (GLA) grant for a new housing zone in Hounslow awarded in January this year.
Work on the council's new home is also due to begin in July next year and it should be ready for staff to move in by July 2018, enabling the demolition of the existing Civic Centre building.
The new Civic Centre will have seven storeys and will be accommodate Hounslow library, which is due to move from its existing home at the Treaty Centre in Hounslow High Street.
The building, which will include a 45-space basement car park, will cost an estimated £56m - all but £0.4m of which the council says will be covered by the sale of the existing Civic Centre for housing.
The new housing development beside Lampton Park will include 340 affordable homes, representing 40% of the total being built on the site.
The council says the move is necessary as its current home is too large for purpose due to the downsizing of its workforce and is expensive to maintain.
Planning applications for both sites, which have yet to be submitted, must be approved before work can begin.