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The RAAC Crisis

25 September 2023

Charlie Green explains why embracing prefabrication is key for safer educational institutions.

In the annals of construction history, materials and methods have evolved, reflecting the needs of the times and the lessons learned from past experiences. Reinforced autoclave aerated concrete (RAAC), a once-celebrated material from the 1950s to the mid-1990s, is now under scrutiny due to its potential risks in ageing structures. The National Audit Office (NAO) report, which sent ripples across the educational sector, underscored the urgency of addressing the RAAC dilemma. With a significant number of schools in England identified with RAAC concerns and many more awaiting survey results, the need for a reliable and swift solution has never been more pressing.

Understanding the RAAC dilemma

Reinforced autoclave aerated concrete (RAAC) was a popular choice in construction from the 1950s to the mid-1990s, primarily due to its lightweight and insulating properties. However, recent findings have spotlighted potential risks associated with this material, especially in ageing structures.

A report from the National Audit Office (NAO) earlier this year highlighted that RAAC had been confirmed in at least 65 schools in England after 196 completed surveys, with 24 requiring emergency action. The Department for Education (DfE) anticipates that the number of schools at risk could increase significantly once the results of surveys from 572 schools with suspected RAAC are completed.

So, why is RAAC a concern? Experts indicate that RAAC is less durable than traditional reinforced concrete. It deteriorates over time and is susceptible to sudden failure. Its life expectancy is just over 30 years, implying that buildings constructed from the 1950s to the 1990s that haven't been inspected by structural engineers are at risk of collapse. Moreover, RAAC is prone to collapse when wet, which can occur if there are leaks in a building’s roof.

The gravity of the situation became evident in 2018 when the roof of a primary school in Kent collapsed just 24 hours after signs of structural stress began to appear. Since then, several schools have had to close, either fully or partly, due to RAAC-related concerns. Others have required emergency propping up owing to fears of collapse.

Prefabricated structures: The future of school construction?

In the face of complications arising from traditional construction materials like RAAC, the construction industry is pivoting towards innovative solutions. One such promising alternative is the adoption of prefabricated structures. Prefabricated structures are buildings or components of buildings that are manufactured and assembled off-site in a controlled environment. Once completed, they are transported to their intended location for rapid assembly.

Advantages of prefabricated construction:

  1. Ensure Compliance with Building and Safety Regulations

Prefabricated structures are emerging as a promising solution in the construction industry, especially given the challenges associated with traditional materials like RAAC. Constructed in controlled environments, prefabricated components are produced under strict quality control measures. This meticulous approach ensures that every component, from the smallest bolt to the largest panel, meets the required standards even before it reaches the construction site.

The consistent quality of prefabricated structures is a significant advantage. A study from MDPI highlights a systematic approach to prefabrication that determines the key factors affecting a building project's quality and safety. Unlike traditional construction, which can be subject to variations due to factors like weather or on-site challenges, prefabrication maintains a uniform quality throughout.

SafetyCulture emphasises the role of specialised equipment and tools in assembling prefabricated structures. This equipment ensures that these structures not only meet but often exceed the building codes set by regulatory bodies. This adherence to building codes and standards is crucial, especially in light of recent concerns with materials like RAAC.

One of the most significant advantages of prefabrication is the reduction of on-site challenges. The issues with RAAC underscored the potential vulnerabilities of on-site construction. By shifting most of the construction off-site, prefabrication minimises these challenges, ensuring fewer errors or oversights during the building process.

Furthermore, the controlled environment of prefabrication means that safety standards are rigorously maintained. As a result, the structures produced are not only durable but also compliant with all safety regulations.

  1. Swift Replacement and Upgrades

The legacy of RAAC in buildings from the 1950s to the 1990s has underscored the need for rapid and reliable construction alternatives. Prefabricated structures are uniquely positioned to meet this demand. As highlighted by LetsBuild, the modular nature of prefabrication can halve construction times compared to conventional methods. This expedited process means that specific sections of a school, whether it's a roof, wall, or an entire wing, can be swiftly replaced or upgraded, minimising disruptions to the educational calendar.

Moreover, the precision inherent in prefabricated components ensures that replacements and upgrades seamlessly integrate with existing structures. Each component, meticulously crafted in controlled environments, aligns perfectly with the next, ensuring a cohesive and sturdy assembly. This precision is invaluable, especially when addressing vulnerabilities in older constructions, ensuring that upgrades not only fit perfectly but also enhance the overall structural integrity.

Furthermore, the streamlined processes associated with prefabrication allow for efficient planning and execution. If a particular section of a school, such as a roof compromised by RAAC, needs replacement, the modular nature of prefabrication ensures that this can be achieved with minimal fuss and maximum efficiency. The components are designed for easy assembly, ensuring that upgrades are not just swift but also of the highest quality.

In essence, as schools grapple with the need to replace or upgrade sections compromised by materials like RAAC, prefabricated structures offer a promising path. They ensure that these replacements and upgrades are executed swiftly, efficiently, and to the highest standards, safeguarding the future of educational institutions.

  1. Sustainable and Safe Materials in Prefabricated Structures

In the realm of construction, sustainability has become a paramount concern. Prefabricated structures have risen to this challenge by placing a significant emphasis on eco-friendly materials that are not only durable but also safe. According to a special issue on sustainable development in prefabrication by MDPI, prefabrication methods offer several benefits, such as a lower environmental impact, reduction in construction waste, material waste, and energy use. These benefits underscore the commitment of the prefabrication industry to sustainability.

Furthermore, a study from ScienceDirect highlighted the thermal and environmental performance of prefabricated components. The research, based on China's construction, showed that using prefabricated components could enhance the thermal performance of buildings. This is crucial, especially when considering the risks associated with materials like RAAC, which, as highlighted by The Guardian, can be problematic, especially when wet.

Prefabricated structures, in contrast, prioritise materials that undergo rigorous testing for various conditions. This ensures that they can withstand diverse environmental challenges, guaranteeing both longevity and safety. Another study from ScienceDirect emphasised the eco-efficiency and building optimization potential of prefabricated structures. The research focused on the analysis of a novel dry precast beam-column connection under different durability and re-using scenarios.

In conclusion, the shift towards prefabricated structures is not just a trend but a necessary evolution in the construction industry. By prioritising sustainable and safe materials, these structures address the challenges posed by traditional materials like RAAC, ensuring that the buildings of the future are both eco-friendly and resilient.

Future-proofing educational establishments

As educational institutions grapple with the challenges posed by traditional construction materials like RAAC, it becomes imperative to explore alternative solutions that not only address immediate concerns but also future-proof schools against similar issues.

Asset management systems, equipped with advanced sensors and data analytics capabilities, can continuously monitor the condition of a school’s infrastructure. By providing real-time insights into the health of assets crucial to safety, such as roofs, walls and foundational elements, these systems can preemptively identify vulnerabilities. A study by the Institute of Asset Management underscores the importance of such systems, highlighting that proactive maintenance, driven by timely data, can reduce unexpected repair costs by up to 20% and extend the life of assets by 10-20%.

Prefabricated construction, on the other hand, offers a robust alternative to traditional building methods. As discussed earlier, its benefits span from quality assurance to sustainability. But when combined with asset management systems, the synergy is amplified. For instance, each prefabricated component can be embedded with sensors that feed data into the asset management system, ensuring continuous monitoring from the point of manufacture to installation and throughout its lifecycle.

In conclusion, the challenges posed by materials like RAAC underscore the need for schools to be agile, informed, and proactive. By harnessing the capabilities of asset management systems and the promise of prefabricated construction, schools can not only address their current challenges but also build a resilient foundation for the future, ensuring that our educational spaces remain safe, sustainable, and conducive to learning.

Charlie Green is senior research analyst at Comparesoft. For more information, visit https://comparesoft.com