The Daily Telegraph - Saturday
Crunch time for concrete: the post-war building spree is tumbling down
Many schools and hospitals built between the 1950s and 1980s are crumbling. Abi Buchanan investigates
Just as children were getting ready to return to school after the summer holidays, the announcement went out that, for the fourth year running, things might not go quite to plan. But this time, Covid or teacher strikes were not to blame.
This year it’s the turn of “crumbling” aerated concrete, which is believed to have been used to build over 150 schools across the country. Thousands of children have been told not to return for the new academic year due to concerns over the soundness of these state-owned structures. Meanwhile, affected schools scramble for solutions, ranging from closing down facilities (such as computer rooms), bringing in temporary teaching spaces (such as Portakabins) or moving entire school populations onto remote learning programmes.
Governments have been warned of the risks posed by reinforced autoclaved aerated concrete (RAAC) since the 1990s, but were compelled to finally act after a beam in one school collapsed without warning over the summer. The Health and Safety Executive (HSE) has declared RAAC
“life expired” and says “it is liable to collapse with little or no notice.”
In recent years, there have been a few worrying indications that RAAC has been reaching the end of its shelf life. In May this year, the Ministry of Defence began conducting urgent surveys of its buildings over concerns about the integrity of hundreds of barracks and training facilities made with RAAC. As far back as 2018, the Department for Education was reviewing the material after a roof at a primary school in Gravesend, Kent, collapsed. So how did Britain become a crumbling concrete jungle?
Although the material itself has been used for centuries, concrete is strongly associated with the UK’s post-war period. The infrastructure and housing decimated by bombing in the Second World War needed to be rapidly rebuilt, and concrete was found to be a quick and inexpensive cure.
“Because of the urgent need to construct houses, schools and hospitals, both Labour and Tory governments in the post-war era desperately tried to out-compete the other by setting higher and higher building targets,” explains John Grindod, author of Concretopia: A Journey Around the Rebuilding of Postwar Britain. “These targets couldn’t be met through traditional methods, which is where concrete and prefabrication came in. In many cases this worked well but, with so much experimentation happening so fast, sometimes instant fixes were favoured over longer-term solutions.”
One such “instant fix” was RAAC, which is commonplace in the roofs and walls of public buildings such as schools and hospitals built between the 1950s and 1980s. It is a type of reinforced concrete made from cement, blast furnace slag and pulverised fuel ash or silica flour mixed with water and aluminium powder. As it is aerated, it has a “bubbly” structure which means it is lighter and cheaper than other kinds of concrete, but weaker and less structurally sound. The air pockets mean it is vulnerable to corrosion – and, as has now been discovered, it can collapse with very little warning.
However, experts are keen to distinguish between this “dangerous concrete” and other post-war concrete buildings, such as the Barbican in the City of London, which are widely celebrated not just for their design but for their build-quality and appearance. “In the hands of a skilled practitioner, such as the Japanese architect Tadao Ando, concrete can be wonderful, both in terms of aesthetics, its longevity and its technical capabilities,” says says Tony Chambers, design consultant and former editor of Wallpaper* magazine. “Unfortunately there are too many examples – particularly post war – where it was misused because it was seen as a way you could do things quickly and cheaply.”
Chambers moved into the Barbican 30 years ago and says it was considered “unfashionable” then. “Whereas now, it’s actually very hip, and you can’t move for fashion shoots or music videos being made.” Concrete is now so in vogue that it’s hard to move through a modern interior without stepping on a polished concrete floor, or putting your glass down on a concrete bar next to a concrete plant pot. In fact, some buildings once considered eyesores by previous generations, such as the National Theatre and the Alexandra Road estate in Camden, north London, are now widely regarded as towering architectural masterpieces.
However, Chambers adds that some 1960s buildings were not fit for purpose, and there were disastrous consequences. Ronan Point, a 22-storey block in east London, partly collapsed in 1968 after a gas explosion, just two months after completion. It was later found to be caused by poor construction and design.
Concrete, as a material, has had a long and illustrious history well before the post-war civic planners and architects took to building back the UK’s blitzed cities. It was, of course, invented by the Romans and used across their vast empire to build everything from public baths to harbours and aqueducts, and some concrete Roman structures have lasted centuries. Yet, following the collapse of the Roman Empire, its consideration as a building material really gained traction in Britain at the beginning of the 20th century, says Dr Barnabas Calder, head of the history of architecture research cluster at the University of Liverpool, and author of
Raw Concrete: The Beauty of Brutalism.
“There was a fair amount of concrete used pre-First World War and lots between the wars, but very often it wasn’t visible. It had brick facing or was just used between floors and that kind of thing. It’s not as obviously a concrete aesthetic. The biggest phase of it being used externally or in prestigious interiors is post 1945.”
After the war, concrete was used “very often for incredibly enlightened [means] – improving education, improving health and improving housing for as many people as they could, which I think it’s very hard not to admire,” he says. “It was a period of change and experimentation. Some of those experiments turned out to be problematic, but most turned out OK.”
Since then, our dependence on concrete as a quick, cheap building fix has just grown – but it’s not without its downsides, as Calder points out. Concrete is said to be responsible for 4-8 per cent of the world’s CO2, half of which is generated during the cement-making process, and is also charged with choking natural habitats and exacerbating human health issues.
Post-war buildings should be protected wherever possible, he argues, not only because of their heritage but because demolishing and replacing them – with yet more concrete – would come at a great environmental cost. The biggest issue is preventing RAAC from causing problems in schools and public buildings, but Calder is also concerned that this will contribute to an unnecessary “suspicion of older concrete”, which doesn’t need replacing and should, wherever possible, be maintained.
“Some may need to be demolished to get rid of this specific problem, but I’m concerned about the possibility of a knee-jerk tendency to increase already too-high demolitions of post-war buildings,” he says, “as the carbon intensity of demolition and replacement is enormous. Most buildings are adaptable and alterable until they meet contemporary needs in a safe and satisfactory way.”
But regardless of how it’s done, as the UK has hundreds of hospitals, court houses, schools plus countless other state buildings created with RAAC, like the generations before us, it looks like we have a rebuilding project on our hands.