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Medway County and Family Court is to relocate to the council's headquarters at Gun Wharf in Chatham.
Its current building at the nearby Anchorage House is being vacated this summer.
For an interim period, court hearings will be held at the Holiday Inn near Rochester Airport before the move is complete.
Council bosses previously said that since lockdown – with 75% of staff home working – the cost of running the riverside offices was not financially viable.
Leader Cllr Alan Jarrett (Con) previously expressed an interest to rent out part of the 1970s' Grade-II listed building in Dock Road to claw back cash.
It costs £2 million a year to maintain with the heating bill alone running to £1.1 million because it is not energy efficient.
Portfolio holder for resources, Cllr Adrian Gulvin, said: “We worked very hard to ensure the court remained in Medway, so residents did not have to travel to other courts across the county.
"We are currently working with HM Courts and Tribunals Service to enable the necessary building works to take place over the next 18 months.”
Rumours have emerged over the last year that the 1,000-strong council workforce could be moving to another premises in the town.
These included the empty Debenhams store in the High Street or Mountbatten House, the 13-storey empty office block above the Pentagon.
A survey of employees found 90% were satisfied with their new flexible working conditions with a significant number preferring to work from home permanently.
Cllr Jarrett has stressed the authority's HQ will remain in Chatham, where it is committed to a multi-million pound regeneration of the town centre.
HM Courts and Tribunals Services has confirmed the lease for current court has expired and the landlord has opted to redevelop the site.
While Gun Wharf is being adapted, court business will transfer to the hotel in Maidstone Road, Chatham.
Delivery director for the south east region, Lorraine Tedeschini, said: "Establishing Gun Wharf as Medway County and Family Court in the longer term means concerns regarding ease of travel are resolved by using a location close to the current court."
The decision followed a consultation last year where the service initially proposed most work be permanently relocated to Maidstone Combined Court.
It said, however, it became clear from the survey that people overwhelmingly wanted to retain the court in Medway.
In a joint submission, family judges in Kent said the proposal to triage every case to identify which needed face-to-face hearing was "unrealistic and unworkable".
Medway County Court is the designated family court for Kent with seven courtrooms, five judges and 32 administation staff at Anchorage House.
Gun Wharf was built as an administrative headquarters for Lloyd's of London and bought by the council in 2006 when the authority moved from an old factory premises on the Esplanade, Strood.