The revamp of the building, which McLaughlin and Harvey began back in 2015, was scheduled to be completed in late 2017.
But Aberdeen City Council today said it now won’t be completed until late 2018 or early 2019.
The reason for the delay has not been disclosed but the Aberdeen Evening News has reported that it understands the project is facing a significant financial overspend.
Aberdeen City Council said: “Contractors responsible for the project are in ongoing discussions with Aberdeen City Council to confirm a completion date for the project, with the Gallery now expected to reopen in late 2018 or early 2019.
A report to the council’s finance, policy and resources committee next month will outline the revised schedule plus “provide further detail on the issues which have led to the extension of the programme and potential budget implications”.
Councillor Marie Boulton, Aberdeen City Council’s culture lead, said: “High level discussions with the main contractor for the Aberdeen Art Gallery redevelopment, McLaughlin and Harvey, are ongoing to finalise a revised schedule for the project.
“Current indications are that the contractor will conclude work on site in the first quarter of 2018. Following the handover from the main contractor a further fit out programme is required before the collections can be returned and the building is prepared for opening to the public.
“The final schedule is subject to the ongoing discussions but it is anticipated opening will be delayed until late 2018 or early 2019.
“This is an important project for Aberdeen and it is imperative that what will be a lasting legacy for the city is completed to the exacting standards required for a development of this significance – but a delay of this nature is unacceptable.
“It is important the issues with the delivery of the project are fully examined and acted upon.
“Measures have already been taken, with the appointment of specialist project manager Faithful+Gould to represent the council in negotiations with the contractor.
“With any building of this age and complexity there will always be complications which can impact on the programme, and that has been the case with Aberdeen Art Gallery.
“However, we are in discussions with the contractor regarding the circumstances of the extension to the programme.”