Aberdeen Art Gallery will remain closed for at least another year after a major delay hit the £30m redevelopment.
The opening of a second city attraction, the 16th Century Provost Skene’s House, has also been put on hold given a fresh condition report on the historic property.
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Aberdeen City Council declined to discuss the causes of the delay at the art gallery, which is seen as having a key role to play as Aberdeen works to draw more visitors and reposition itself as a culture and arts destination.
A report on the reasons behind the revised opening date and any potential budget implications is due to be discussed by councillors on December 1.
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The gallery, which is due to get a new rooftop extension, closed in March 2015 as the redevelopment, which is being funded by a mix of lottery money, public funds and donations, got underway.
Work was halted for six weeks after a medieval cemetery was found under the building last year.
However, it is understood there is no single cause of the current delays at the “complex” building.
Councillor Marie Boulton, Aberdeen City Council’s culture lead, described the delay as “unacceptable.”
She said: “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.”
Construction is likely due to finish in Spring 2018 with the building then to be fitted out to allow the collections to return.
Cllr Boulton added: “The final schedule is subject to the ongoing discussions but it is anticipated opening will be delayed until late 2018 or early 2019.”
Talks are ongoing to finalise a revised schedule for the project.
A spokesman for the company refused to comment.
Meanwile, the re-opening of Provost Skene’s House was due to reopen as a visitor attraction in 2017 but, following a condition survey, options for the refurbishment are to be considered.
The historic building is now enveloped by the Marischal Square development of offices, restaurants and bars.
Cllr Boulton added: “Protecting Aberdeen’s built heritage is a priority for the Council and it is important that the latest information is taken into account.”