St David's Hall will now remain closed until 2025, Cardiff Council has announced.
A report into ‘potentially dangerous' concrete panels in the venue recommends that the building's roof needs to be completely replaced.
The report was commissioned by the council following changes to Health and Safety Executive (HSE) advice on Reinforced Autoclaved Aerated Concrete RAAC in public buildings.
Over the past few months several buildings have closed across the UK due to concerns over RAAC - a building material which the HSE said was now past its intended lifespan and is liable to fail without warning.
RAAC experts have been at St David's Hall for several weeks carrying out ‘intrusive' tests on panels across the span of the building's roof.
Their report noted that a significant number of the 900 plus panels in the roof are ‘red - critical' and others ‘red - high risk' meaning they could fail and collapse. Engineers recommend the venue stays closed either until emergency temporary mitigations are put in place, or the whole roof is replaced.
Temporary mitigation would take at least six months to install and is likely to cost several million pounds, but the entire roof would still have to be replaced at a cost of many more millions within a relatively short time.
The council's cabinet has therefore recommended fixing the roof in one go enabling the venue to reopen for the long-term.
St David's Hall was in the process of being leased to the Academy Music Group (AMG) which is aware of the RAAC in the building and had committed to refurbishing the venue and dealing with the roof issues as part of the original lease agreement.
Under the original lease agreement, AMG had planned to keep St David's Hall open with only short closures while repairs were carried out, but the findings of this new report now point towards a complete closure to enable a new roof to be installed and a refurbishment of the venue to take place. This could take around 18 months to deliver.
The replacement of the St David's Hall roof will be complicated and costly for the following reasons:
the city centre location in the Hayes;
the height of the roof/ceiling;
the building has recently been listed as having special architectural and historical interest;
the requirement to preserve the acoustic quality of the venue;
the likely requirements for planning permission.
AMG has confirmed it remains committed to investing in St David's Hall and proceeding with the proposed transaction previously agreed by cabinet in the July 2023.
However, considering recent developments, AMG has asked for the lease being conditional for a period to enable them to identify a viable solution and to secure planning permission and listed building consent for the required works.
Entering a conditional lease will provide AMG with the assurance it needs to spend money up front to undertake detailed design works and to submit applications for planning permission and listed building consent. Once these are achieved, the lease would become unconditional in advance of AMG undertaking the works. The costs of undertaking the design works will be at AMG's risk.
AMG is targeting a reopening well in advance of the next BBC Cardiff Singer of the World competition in July 2025.
All other conditions of the lease, including protecting the classical calendar when the venue reopens, would be adhered to.
A council spokesperson said: "We know this will cause a lot of inconvenience and disappointment for our customers, but we hope they will understand that the safety of audiences, staff, artists, volunteers, and everyone at the venue is paramount.
"We will be in contact with promoters and hirers to discuss the potential for moving performances to other venues. There is no need for customers to contact St David's Hall, we will be in touch with all ticket holders about options available to you once we have spoken with each affected show's promoter. We would be grateful if customers could give us the space to undertake this work so that we can come back to you as quickly as possible about your ticket purchase/cancelled event.
"The council has been consistently clear on the need for investment into St David's Hall to secure its long-term future, addressing the RAAC and other maintenance issues, all of which was confirmed in a cabinet report last year.
"Once again, we apologise to customers of St David's Hall for the late cancellation of shows, and we want to reassure you that we will be in touch to discuss rescheduling of performances and/or alternatives. Please follow the St David's Hall website's news section, for updates. Thank you for your understanding and patience."
Council's Economy and Culture Scrutiny Committee will take the report next Tuesday at its 5.15pm meeting, on October 24. You will be able to watch that committee meeting on a live stream on the day here.
Cardiff Council's Cabinet will then take a decision on the report at a meeting on Thursday, October 26, which will also be available to view online.