Conlon Construction has been given more time to finish the £16m refurbishment of The Harris museum and arts centre.
The contract was due to finish by the end of next year but the opening date has now been pushed back to Spring 2025.
The move follows complications in renovating the 130-year-old building including extra fire protection works, large-scale asbestos removal and boiler replacements.
Plans for installation of an additional lift into the building have also been dropped.
Michael Conlon, Chairman of Conlon Construction, said: “Together with Preston City Council and designers, we have an outstanding project team. We’re all committed to delivering an exceptional visitor experience that honours one of our city’s most culturally significant landmarks.
“It’s a rare privilege to act as custodians during the restoration of such an important Grade I listed building. As has often been the case in our experience with numerous heritage projects, the 130-year-old building has revealed some hidden secrets.
“These will require careful and sympathetic attention to ensure its preservation for future generations. The final result will be remarkable, and we’re all focused on ensuring ‘The Harris’, known and loved by the people of Preston, continues to play a crucial role in the city’s future.”
Councillor Peter Kelly, Cabinet Member for Arts and Culture at Preston City Council said: “The Council fully supports The Harris’ decision to extend the reopening date. We recognise the importance of preserving our cultural heritage, and this extension ensures that the necessary work can be completed to the highest standards.
“We appreciate the public’s continued support and patience as we work diligently to ensure a long and ambitious future, accessible for all.”