Work to refurbish York Guildhall will begin in September.
Senior councillors approved £20m plans to refurbish the historic building at a meeting in February.
A fresh planning application submitted for the site in May says repair work would be carried out on the building and conference rooms, meeting rooms and offices would be created at the complex.
Part of the south range would also be rebuilt to provide a cafe, while an extension would be built on the north side to create a riverside restaurant and more offices.
Cllr Nigel Ayre, executive member for finance, said:
The investment in the Guildhall will protect the historic building for many years to come; restoring its place at the heart of York’s social, civic and business life.
The council has had positive conversations with the preferred bidder and are close to confirming the full work programme, which will see the vital restoration work begin this September.
Price rises by £20m
Construction work was due to begin in the spring but a report prepared for a City of York Council meeting next week says it will start in September.
The report says: “We look forward to bringing this historical site back into operational use for the city, opening up the building to the public and providing new small to medium enterprise growth space and animating the riverside.”
Initial investigations revealed that the building needs more repair work than expected.
Councillors heard at a meeting in February that the site is currently costing the authority £125,000 a year to keep empty.
And once it is refurbished it could create 250 jobs and bring in £117 million over the next five years.
Plans to transform the complex were first proposed in 2013. Since initial proposals, which put the estimated cost of the project at £9.23 million, the price has risen to more than £20 million.