What is RAAC? Why aerated concrete school buildings must close in England and the safety fears explained

Jun 30, 2023

Thousands of pupils across the country face being forced to return to remote learning when they begin the new academic year next week, after the Government ordered the urgent closure of school buildings at risk of collapse.

The Department for Education (DfE) announced it has contacted 156 schools in England warning them that their buildings contain a dangerous substance called reinforced autoclaved aerated concrete (RAAC).

Of those, 52 schools have already received repair works in the past few months, but 104 require urgent action.

Government sources told i this means a “small minority” of schools will be forced to begin the year with a return to remote learning as buildings are considered too unsafe for pupils to return to classrooms.

RAAC is a lightweight, precast, cellular concrete building material made from quartz sand, calcined gypsum, lime, portland cement, water and aluminum powder.

It started being used predominantly in public sector roof construction in the UK and parts of Europe in the 50s and continued to be used until the 90s, but the material has been found to have structural issues that means it begins to deteriorate after 40 or 50 years. That means much of the RAAC that remains in British buildings is now at risk of causing a collapse.

Professor Chris Goodier, an expert in construction engineering and materials who led a major national research project on RAAC for the University of Loughborough, explains: “Like many countries, the UK has an old building stock, which needs to be adequately repaired and maintained. In the post-war period the country built numerous new buildings with a variety of different methods, many of which are now feeling their age.

“One innovative construction material and process was RAAC, which is an aerated lightweight cementitious material with no coarse aggregate; the material properties and structural behaviour therefore differs significantly from ‘traditional’ reinforced concrete.

“Tens of thousands of these structural panels exist across a broad cross-section of buildings, many constructed in the 60s and 70s, and many are showing signs of wear and tear and deterioration. The vast majority form the roof of the structure, usually flat, and hence are difficult to access, survey, maintain and replace.”

A report published in May 2019 highlighted the significant risk of failure of these planks and in September last year the Government sent a notice to relevant property owners stating that “RAAC is now life-expired and liable to collapse”.

Professor Goodier said it is RAAC “from the 50s, 60s and 70s that is of main concern, especially if it has not been adequately maintained”.

“RAAC examples have been found with bearings (supports) which aren’t big enough, and RAAC with the steel reinforcement in the wrong place, both of which can have structural implications. Prolonged water ingress (not uncommon on old flat roofs) can also lead to deterioration,” he said.

However, not all RAAC is dangerous by nature. It is s still manufactured and installed all over the world and can be an appropriate construction material if properly designed, manufactured, installed, and maintained.

The Government warning has left headteachers scrambling to draw up contingency plans just days before students are set to return from the summer holidays.

Some schools have been told they must erect portacabins in school playgrounds, while some schools have been advised to find urgent “off-site accommodation” for pupils.

One Tory MP told i the Government’s failure to act on the saga over the summer had resulted in “utter chaos”.

Another said there “should be calls on ministers to disclose what they knew and when” and asked: “Why did they leave it so late to take action? We don’t know why the DfE did nothing about this over the summer and get repairs done to the schools.”

Senior Tory sources told i that they were briefed on the issue by ministers on Wednesday night, just days before children are set to return to the classroom following the summer holidays.

The DfE said it took the decision to force schools to close out of “an abundance of caution and to prioritise safety of children, pupils, and staff ahead of the start of the new term”.

It said parents will be “contacted by their school if pupils are moving to a temporary location while remediation works are being carried out”.

The Government refused to name the schools affected or to publish a regional breakdown, but said it would provide an update in due course.

Bridget Phillipson, the shadow education secretary, said: “This is an absolutely staggering display of Tory incompetence as they start a fresh term by failing our children again.

“Dozens of England’s schools are at risk of collapse with just days before children crowd their corridors. Ministers have been content to let this chaos continue for far too long.”

Unison’s head of education, Mike Short, said: “This situation is nothing short of a scandal. The DfE and Government have squandered valuable months hiding this crisis when they should have been fixing dangerous school buildings.

“The schools minister even broke his own promise to publish information about at-risk properties before Parliament’s summer recess.

“Parents, pupils and staff will be relieved the issue is finally being taken seriously. But to wait until the 11th hour as schools prepare for a new academic year will create turmoil for thousands of families. And this could just be the tip of the iceberg.”