After years of uncertainty, the historic Preston Guild Hall was set to open in 2024, only for those plans to be thrown adrift due to the need for urgent and extensive concrete repairs.
The reason for this, as announced speculatively in September 2023 and confirmed in January 2024, was due to the presence of reinforced autoclaved aerated concrete in its roofing panels, which in 2023 led to hundreds of urgent roof repairs due to the material’s unpredictability.
The use of RAAC as a construction material started in 1929, but became very popular in the mid-1950s as a lighter, cheaper version of reinforced concrete, with the material being particularly good when it came to fire and seismic resistance.
This is why several major airports, hospitals, York Castle Museum, the Palace of Westminster and many schools and universities used the material for four decades until an incident in 1995 started to suggest that RAAC was not necessarily as safe as was initially believed.
The issue was not just that the concrete would deteriorate over time, but that it was prone to sudden failures without warning, so it stopped being used but this meant that any buildings that were built using the material were at risk of having components suddenly collapse.
This fear, one that structural engineers had voiced for nearly two decades, ultimately would come to pass in August 2023, with 174 schools in the UK closing after a RAAC beam suddenly collapsed.
This included Preston Guild Hall, an entertainment complex constructed in 1973 that was set to be reopened after a somewhat tumultuous period of administration.
After being saved from potential demolition in 2014 and being reclaimed by Preston City Council due to the “unacceptable behaviour” of its previous owner, it was expecting to be refurbished and reopen with an event in 2023, but the discovery of RAAC two months before put any of these plans on hold.
Much like with asbestos, RAAC needs to be managed by a specialist, and depending on how much has been used, it can sometimes be the case that outright rebuilds are less complex than repairs.