Leeds Town Hall was designed by architect Cuthbert Brodrick and was one of the largest town halls in the United Kingdom when it was opened by Queen Victoria in 1858.
The extent of the damage to the building from the bombing and subsequent repairs has meant urgent structural work was needed to make the site safe, according to Leeds City Council.
Dan Doherty, regional director for contractors Kier Construction North and Scotland, said: “With heritage building projects, it’s often only once construction begins that we start uncovering layers of history and discovering unexpected aspects of the building’s story – and this of course means we have to adapt our original plans.”
Conservation and repair of key features, including stone masonry, delicate plasterwork and doors, are also planned to protect and preserve the building’s heritage.