A Brief History of RAAC

Starting its journey in Sweden around the mid-1920s, RAAC quickly gained traction after being patented in 1924. Just five years later, production took off.

Ever wondered what makes this material so unique? It's all about the blend! RAAC is crafted from natural materials like sand, lime, gypsum, and cement, aerated with agents like aluminum and then strengthened in an autoclave through vapor.

Why all the buzz around it? Its lightweight nature makes it a dream, being just a third of conventional concrete's density! Plus, it's budget-friendly. Its reduced weight means fewer supporting structures, which translates to savings. Faster construction and impressive thermal insulation? That's the cherry on top.

Understanding Compliance

Many standards have governed RAAC over the years. From CP 116:2 :1969 to EN 12602 2 (withdrawn in 2018), compliance has been a journey.

The BRE Information of the late 90s and early 2000s, the Standing Commission on Structural Safety in 2007, and the 12th Report of SCOSS in 1999 shed light on RAAC's journey and potential issues.

RAAC's Impact in the UK

Between the 1950s and the early 90s, the UK embraced RAAC with open arms. Even today, several countries, especially in East Asia, produce RAAC products.

Its primary use? Roofing and flooring panels, and walls. Educational institutions, healthcare facilities, defense buildings - they all saw RAAC as the future. Interestingly, the Ministry of Works, replaced by the PSA in the 90s, endorsed it.

Did private sectors use it? Certainly! Especially in offices and retail establishments. Although, pinpointing its exact usage remains tricky. One fun fact: BRE sampled planks from a housing project in 1991. However, RAAC's role in residential areas is still a mystery.

Navigating Compliance & Limitations

By 2007, a shift towards "Good Practice in the Selection of Construction Materials" was evident.

AAC blocks were often mentioned in warranties, but RAAC planks? Not so much. Even though RAAC's performance was questioned, its harmfulness was often debated.

Time frames play a role in understanding RAAC's journey, from contracts and torts to the S.14B 15-year long-stop. A notable date? 28 June 1992, 30 years before BSA's introduction.

Known Challenges

Every rose has its thorns, right? RAAC's challenges include deflections, cracking, corrosion, and issues with load sharing, among others. But hey, no material is perfect!

Steps Forward: Investigations & Solutions

Identifying problems is half the battle. From thorough assessments by surveyors to detailed analyses by engineers, solutions like improved end-bearing, removing individual panels, or even complete roof replacements have been explored.

The goal? Ensure RAAC's longevity and safety.

Risks & Ramifications

Designers, architects, and engineers faced risks, especially in design & build projects. Surveyors grappled with challenges like identifying RAAC issues within a six-year span or dealing with remedial work costs. Even Facilities Managers in PFI contracts faced their share of hurdles.

Insurance Implications From notifying to understanding product exclusions and the retroactive date, RAAC had its influence on insurance policies.


RAAC, a material with a rich history and impact, has its advantages and challenges.

Key takeaways? Understand limitations, be open to remediation, and keep an eye on potential legislation.

What exactly is RAAC?

RAAC, or Reinforced Aerated Autoclaved Concrete, is a lightweight construction material originating from Sweden in the 1920s.

Why was RAAC popular in the UK?

Its lightweight nature, cost-efficiency, and thermal insulation made it a preferred choice for construction projects.

Were there any concerns with RAAC?

Yes, like most materials, RAAC had its set of challenges, including deflections, corrosion, and cracking.

How has RAAC impacted the insurance sector?

Insurance policies had to consider RAAC-related notifications, product exclusions, and retroactive dates.

What's the future of RAAC?

While RAAC's popularity peaked in the 20th century, its influence, learnings, and legacy continue to shape the construction world.


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