School buildings hazards explored

What could be be the next RAAC scandal?

‘It’s a cheap way to get you out of a pickle in the short term’

Timber rooves held together with ‘glue and panel pins’ and materials that turn to ‘fragile Weetabix’ when wet are ticking timebombs in our school buildings, finds Jessica Hill

A swollen national debt, depleted construction force and baby boom after the Second World War made Britain desperate for new ways to build schools cheaply and quickly.

Many of the quick fixes – from lightweight cement to hollow concrete blocks embedded in asbestos – were then forgotten about for decades.

Now the Department for Education is finally commissioning a £4.8 million research project into the structural dangers of post-war buildings, two years after it was proposed.

Matt Byatt, the immediate past president of the Institution of Structural Engineers, believes there is “a whole legacy” of buildings that have been forgotten about.

“Several new technologies were tried and adopted in the 1950s and 1960s. Those buildings have not been maintained as well as they should have been.”

Matt Byatt immediate past president of IstructE

‘System-build’ stresses

Of the 64,000 school buildings across England, 13,800 (22 per cent) come under the loose banner of “system-build blocks”. There are 12 known types made from concrete, steel and timber.

Of these, 3,600 (26 per cent) “may be more susceptible to deterioration”, a National Audit Office (NAO) report last year found.

Like those made with RAAC (reinforced autoclaved aerated concrete), most system-build blocks are fragile structures, now at double their recommended shelf life of 30 to 40 years.

But repairing or replacing them often involves disturbing the asbestos buried within them.

As of last year, the DfE knew of six system-built blocks fully or partially closed since 2017 because of structural instability.

But officials don’t know exactly how and with what materials these post-war schools were built. The DfE’s own condition data collection surveys (CDCs) are only simple visual assessments.

Schools Week analysis of CDC surveys carried out between 2017 and 2019 found 987 system-built school structures referred to as “unknown” type.

Laingspan and Intergrid

Laingspan and Intergrid are two light-frame concrete systems that sit with RAAC at the top of the DfE’s priority list. They were used in the 1950s and 1960s to speed up construction and economise on steel, and were found in two buildings that closed urgently, one following the collapse of a wall, the NAO said.

The union Unison warned “there is the potential for a catastrophic collapse” of these structures.

In March, schools minister Damian Hinds said 24 schools had such buildings. All but one are now part of the school rebuilding programme.

Unison last year accused the DfE of knowing about the risks for “at least a number of years” but not communicating the risks with “staff, pupils or parents using those buildings on a daily basis”.


Short for the “Consortium of Local Authorities Special Programme”, these buildings were prefabricated with a steel framework. There are 1,644 such school buildings in England.

Their structures make them vulnerable to fire, so asbestos boards lined the steel. They are also prone to crumbling and easily damaged. While some local authorities replaced them over the decades, others didn’t.

Former Labour schools minister Lord Knight chairs the E-Act trust. He claims one of its schools built using the CLASP system – Willenhall Academy in the West Midlands – is now “teetering” with weak foundations. Fixing the issue is a “£10 million-plus [job]”.


A similar system, called Second Consortium of Local Authorities, was used in the construction of 767 school buildings from the 1960s on. It was often poorly insulated, contained asbestos and had a 25-year lifespan.

A quarter of Scola schools were built in Hampshire, where the council admits they’re now “well beyond their estimated initial design life”.

Rather than embarking on expensive rebuilds, the council is “recladding” as its annual school capital funding grant of £23 million is “insufficient”. At current funding levels and pace of improvement, some of its Scola buildings will have to “wait a further 20 years to be improved”.

A primary school roof built in the 1950s with an unusual hybrid concrete and steel strand truss which<br>collapsed with no warning

Folded plate timber roofs ‘held with glue and panel pins’

Some dangerous construction techniques only reveal themselves when it’s too late. Two school hall roof collapses in 2011 and 2019 were linked to the failure of folded timber roofs over school halls.

In both cases, the structural engineer who reported concerns to the safety body Collaborative Reporting for Safer Structures UK (CROSS-UK) concluded the end blocks were only held together with glue and panel pins.

They warned “a significant number of these roofs…could exist, and users of such buildings may be at significant risk”.

Another engineer reported in May 2023 how a 1950s primary school roof with an “unusual hybrid concrete and steel strand truss” in the north west collapsed with no warning. Its design was “inherently defective”.

Fordley Primary Schools cracked ceiling

Concrete crisis

It’s not just the RAAC that’s crumbling. In the past six months, four schools in North Tyneside have been found to have used an inappropriate pour of concrete – the “hollow block and beam plank” method. This led to their partial closure.

Concrete fell from a computer suite ceiling and multiple roof cracks were discovered in Fordley Primary School. The council found three other schools – Churchill Community College, Hazlewood Primary School and Grasmere Academy – had the same problem. They were built by different companies.

Jon Ritchie, the council’s resources director, describes it as an “extremely complex situation that’s occurred on a large scale” in the four schools.

Fordley’s headteacher Claire Withers says she’d be “very surprised” if the issue was “just limited to this area”.

She claims the DfE, which says the construction issue is “historic and isolated”, was “not very keen” for the council to share the problem more widely. But the local authority insisted other councils and academy trusts knew about it.

Some of Fordley and Churchill’s children are bussed to other schools, while Grasmere’s are crammed into other buildings and Hazlewood’s make do with outdoor toilets and a marquee.

Cardinal Newman Catholic School in Luton was also built using “hollow” concrete blocks. Cracks in the ceiling forced buildings to close with some pupils taught remotely.

What can happen when a roof is subjected to excessive loads from ponding of rainwater


Other schools were built using high alumina cement concrete (HACC).

In 1973, the collapse of Camden Girls’ High School’s hall roof in north London, blamed on HACC, prompted the hasty closure of some other schools. It was banned in 1976 because it degrades rapidly when exposed to chemicals or water.

IStructE warned in 1997 that “the matter of seriously defective HACC roofs does not seem to be widely understood”.

Woodwool and stramit

Woodwool – shredded timber bound in a cement paste – was used extensively in the 1960s and 1970s, often in the roof decks of system-builds.

It’s similar to stramit, a strawboard insulation made from fused wheat or rice straw used in the same decades. Both are flammable and often laden with asbestos.

These materials cause no problems as long as they’re kept dry. But that’s getting harder to do with the DfE estimating that nearly half of schools (10,710) are at risk of flooding. That’s expected to increase to as many as 16,394 by the 2050s, with scientists predicting severe storms to become more common.

Tim Warneford

Academy funding consultant Tim Warneford says water-damaged woodwool and stramit are the two biggest building safety issues that keep him awake at night.

He recently declared the sports hall at All Saints Academy in Bedfordshire a “no-go area” because of “vertical and horizontal cracks in the woodwool and the weight of rainwater pounding on their roof”.

A recent governors’ report for the school said “academy reserves will not cover the cost of repairs/replacements”.

Sean McGinty, a technical manager for Sike Roofing, describes stramit as being like “fragile Weetabix” when wet. About one in five of the surveys he has undertaken in schools finds stramit or woodwool in their structures.

“Like RAAC, [these structures] could collapse at any time,” he says.

Solar strain

In a cruel twist of fate, installing solar panels on rooftops is also creating safety concerns.

A 2021 CROSS-UK report highlighted “dangerous assumptions” in assessments for the instillation of solar panels in schools that did not take into account the existing structure and load of roofs and did not calculate additional weight correctly.

The increasing use of air source heat pumps and air conditioning condensers are also adding weight and strain to rooftops.

Solar panels

Modern methods of construction

National problems that led post-war school buildings’ problems – a swollen national debt and labour force constraints – have returned.

The solution has been modular structures built using modern methods of construction (MMC), promoted through government initiatives.

But at least seven such schools built or partially built since 2020 are now earmarked for demolition because they are structurally unsafe.

In February, CROSS-UK reported a “systemic issue” with modular timber frame systems, detailing six common flaws with their design and construction.

These include issues with fire stopping, structural element protection, protection of connections and, in particular, “cavity barriers to the voids created when modules are fitted together to form multi-storey buildings”.

Of the ten companies contracted to build schools in 2021 under the DfE’s £3 billion offsite schools’ framework, two have gone into administration.

An online brochure for the new Harrier Primary Academy in Essex, which gives an opening date of 2020, shows children playing at being construction workers laying bricks . But the DfE shunned the bricks and mortar approach to build the school, contracting Eco Modular Buildings Ltd.. The company collapsed in March 2023 and the school still has no opening date.

Eco Modular had also been contracted to build The Flagship School, a special school in Sussex which remains unfinished after an opening date of last September.

The school’s last Ofsted report from 2022 found “problems caused by temporary accommodation” meant leaders’ “capacity to do anything other than react to day-to-day events” had been “severely restricted”.

Buildings at three almost-new schools will be demolished due to safety concerns
Sir Frederick Gibberd College in Harlow

Preventing ‘floor rot’

James Emery, a sales manager for modular builders Wernick Buildings, says his company always ensures buildings have underfloor ventilation to prevent “floor rot”.

But he has visited schools built by other companies that “sunk the buildings into the ground without any ventilation”.

By the time problems emerge, the original contractors have “walked away” as their warranties have expired.

Caledonian Modular, which went into administration in 2022, built Haygrove School in Somerset, Buckton Fields Primary School in Northampton and Sir Frederick Gibberd College in Harlow, which were all ordered to close. Surveys found Sir Frederick Gibberd could not withstand “very high winds or significant snowfall”.

Byatt says it’s “almost as though we’ve come full circle” with the “quick-fix” construction problems of the past.

He sees MMC as “a quicker, cheaper way to get you out of a pickle in the short term. But if they’re not maintained – and we know that these schools are not maintained because they simply haven’t got the budgets – then it deteriorates.”

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