Work on the 拢15m project is expected to start this autumn.
The repurposed building on Swansea鈥檚 Oxford Street will also house other public-facing council services, creating a 鈥榗ommunity hub鈥.
Council leader Rob Stewart said: "The transformation of this building is hugely exciting. It's really good news that Kier Construction are on board with this project. They are one of Britain's leading construction companies with huge experience in converting existing buildings for new uses.鈥
He said: "Kier helped us build the Bay Field Hospital for the NHS during the pandemic against very tight deadlines and were responsible for improvements at YG Gwyr and YGG Tan-y-Lan which have been warmly welcomed by pupils and parents alike.
"The community hub will create a fantastic new library and local services hub in the city centre, right next to the planned new Castle Square Gardens which is currently out to consultation ahead of consideration by the planning committee.鈥
He added: "The project will be a fine example of sustainable city centre redevelopment, reinvigorating existing buildings, and reducing carbon use in the fight against climate change. Between them the current Central Library and archive services get around 300,000 visitors a year 鈥 that's a lot of extra footfall that will boost city centre shopping and jobs on top of the benefits of the arena and Castle Square, which is subject to planning approval."
Kier Construction regional director Jason Taylor said: "We are thrilled to be working with Swansea Council on another project that will support the local community. We will soon be commencing the enabling works for the new Swansea Community Hub scheme, which is located in the city centre and will provide important facilities for local people."
Architect for the project is Austin-Smith:Lord and lead consultant is Coreus.
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