The project to create all-under-one-roof 'community hubs' had been expected to cost the city council £3.3million. But bosses have now revealed that they have had to find the extra £1.03m to bring the buildings up to scratch before the project can move forward.
Senior Labour councillors have agreed to find £475,000 from existing budgets as well as borrowing £554,000 to get the work completed.
Anthony Ivko, Wolverhampton City Council's assistant director for older people, said: "This is maintenance work which would have been carried out irrespective of whether the buildings were going to be turned into community hubs or not.
"As these buildings are now being developed as hubs, however, the work will be brought forward to ensure that it is completed before they open.
"In addition, the design of the community hubs – which have been drawn up with the help of the local community – requires alterations to the layout of many of the buildings, and, therefore, this provides a good opportunity to complete the work in one go."
The plans, which will save the local authority £1m a year, were first unveiled last year and sparked anger among library users, who claimed the moves would 'rip the heart' out of their community.
Thousands of people signed petitions objecting to the plans, forcing council bosses to drop some of their original proposals.
But it is ploughing forward with plans to move Warstones, Spring Vale, Ashmore Park and Collingwood Libraries.
Council chiefs have revealed that the sites at Long Knowle and Wednesfield will be open by December while three more at Ashmore Park, Pendeford and Parkfields will open next spring.
The two remaining sites in Lower Bradley and Low Hill will follow later.
Warstones Library is to move to Warstones Resource Centre. Spring Vale Library is going from its site in Hateley Drive to the former Parkfield High School.
Collingwood Library is to move from its site in Broadway, Bushbury, to sheltered housing scheme Broadway Gardens. Ashmore Park's Library is moving into the area's youth centre on Griffiths Drive. Youth centres including Low Hill, Mirage in Pendeford and Oakley Buckley Youth Club in Penn are also set to move in with libraries.