Reinforced Autoclaved Aerated Concrete (RAAC) has been a notable material in the construction industry, extensively used between the mid-1950s and mid-1990s to form roof planks, wall panels, and occasionally floor planks. It offered a lightweight, innovative solution, marking an era of experimentation and advancement in building materials.

When properly designed, manufactured, and well-maintained with adequate bearing, RAAC installations are deemed safe. However, concerns have emerged regarding the potential creeping and deflection of the panels over time, with risks exacerbated by water penetration. Instances of structural compromise, resulting in fracture and collapse, have prompted critical reassessment of RAAC’s reliability.

In light of these challenges, comprehensive guidance on RAAC has been issued to empower building managers and consultants in managing its associated risks. A dedicated RAAC working study group has been established, accompanied by a roster of professionally qualified structural engineers experienced in offering technical solutions for managing RAAC planks.

Together with the Collaborative Reporting for Safer Structures UK (CROSS-UK), the recommendation for building owners and managers overseeing buildings from this era is clear: undertake thorough inspections and risk assessments. In the presence of RAAC planks, a Chartered or Incorporated Structural Engineer must determine their structural condition, with guidance provided by the IStructE on investigation and assessment. Depending on the findings, ongoing monitoring, remedial propping, strengthening works, or even plank removal or replacement may be essential.

The government’s advice, issued on 31 August, for school building operators to meticulously manage areas where RAAC is present, underscores the urgency of addressing these concerns. The industry continues to work collaboratively with stakeholders, advocating for the inspection of buildings to ascertain the extent of RAAC usage and manage the emerging issues.

RAAC, a unique composition, presents distinct material properties compared to conventional concrete. While challenges such as high deflection, corrosion, spalling, and potential collapse exist, it is essential to contrast this with the reliability of traditional concrete. Conventional concrete, especially when reinforced, showcases high compressive strength, forming the backbone of some of the world’s most substantial structures, from high-rise buildings to bridges and dams.

As we navigate the complexities and legacy of RAAC, the commitment to ensuring safety and managing risks remains paramount. The industry’s proactive stance, coupled with government guidance and ongoing inspection and assessment, highlights the balance between embracing innovation and upholding the highest standards of structural integrity and safety. The lessons learned from RAAC’s history will undoubtedly shape the future of construction materials, fostering a more resilient and sustainable built environment.