By Danielle Aumord.

Building Research Establishment (BRE) staff have admitted that they knew that aluminium composite material (ACM) was not suitable for use on any high-rise buildings (7–17 February 2022)

The back story to the warnings about ‘Class 0’ classified ACM actually started over 30 years ago with a tower block fire in Knowsely Heights, Merseyside in 1991.

This tower block could be described as a guinea pig project – a government-funded pilot scheme to test the efficacy of cladding as a means to insulate council tower blocks. It was being monitored by central government and the BRE, the testing and research facility that was a part of the British state until it was privatised in 1997 and had to bid for contracts to earn its keep.

The fire at Knowsely Heights ripped up all ten floors of the building and by the time the fire service had arrived, the roof was even on fire.

The inquiry into the Grenfell fire heard that was 30 years before the fatal tragedy in West London. Warnings that the standard of ‘Class 0’ fire safety product classification was too low were repeatedly missed. The blaze in Merseyside should have been enough to highlight the potential for disaster associated with cladding.

‘Class 0’ is an old, out of date national product classification which is based on two, old small-scale tests on individual products or materials: BS 476-6 and BS 476-7. These tests only deal with the spread of flames over the surface of a material or the surface of a composite product.

But ‘Class 0’ tests don’t measure the combustibility of a material or the combustibility of the core of a composite material such as ACM. ACM, which Grenfell was wrapped in, is a flat panel made from two thin aluminium sheets bonded to a non-aluminium core, between three and seven millimetres thick.

The BRE’s report into the blaze at Knowsely Heights, revealed by the inquiry into the Grenfell fire, showed that the cladding panels used were glass reinforced plastic (GRP), possessed a ‘Class 0’ rating and were combustible.

But rather than highlighting this in their report, they instead used a few paragraphs to say that cavity barriers were not fitted and noted that “under [official] guidance at the time [cavity barriers] could be omitted where the cladding system was non-combustible”.

Cavity barriers are intumescent substances, used for sealing cavities and voids in buildings. These substances swell as a result of heat exposure, which leads to an increase in volume and decrease in density and this is meant to thwart the movement of fires through the cavity, which can spread to another compartment of the building.

In light of this evidence, Kate Grange QC, counsel to the Grenfell Tower Inquiry, asked: “Can we agree that the clear inference of that paragraph is that this was a non-combustible system, otherwise why would that sentence read as it does at the end?”

“I’m sorry, I can’t speak for what the authors were suggesting with that,” replied the BRE’s Dr Sarah Colwell.

But the same description was also used in a summary report of cladding fires, produced by the BRE in 2016, which Dr Colwell was listed as having signed off.

She explained this by saying it simply followed the original report but didn’t endorse it.

We also heard evidence about investigations into the BRE after the Grenfell fire.

The United Kingdom Accreditation Service (UKAS), which regulates the BRE, is intending to carry out surveillance visits of the organisation in the near future after it learnt through an Inside Housing report of the inquiry that a test carried out on Kingspan’s K15 insulation in 2005 had been withdrawn because it “was not representative of the K15 product which has been sold by them from 2006 onwards”.

David Metcalfe, director of the Centre for Window and Cladding Technology (CWCT), also had clear warnings of the issue of ‘Class 0’ classifications.

The CWCT is an industry body supported by around 350 companies, which the inquiry heard has a two-tiered system of membership that allows higher fee-paying “sponsors” to “buy the right” to sit on its technical committees. Their membership structure has raised questions about whether those higher fee-paying “sponsors” who sit on their technical committees create bias in the policies and guidance produced by the organisation.

In July 2014, they held a fire safety meeting attended by a number of BRE staff, including Dr Sarah Colwell, where the issue of ‘Class 0’ was raised specifically in relation to ACM. The meeting’s minutes record the statement that ACM products which claimed to achieve ‘Class 0’ were being widely used on British shores, making a repeat of the huge fires in the Middle East a possibility.

At the time Dr Colwell claimed that this shouldn’t be happening. She said ‘Approved Document B’ banned the use of such combustible cladding by virtue of a paragraph which required insulation to meet the higher standard of ‘limited combustibility’.

But ACM is not actually insulation, so this caused some confusion at the meeting.

“We were surprised to hear what Sarah Colwell had to say, and we would have certainly questioned how [she] reached that conclusion because it didn’t seem logical to us,” Mr Metcalfe told the inquiry. “We were being offered an interpretation or a view that didn’t appear consistent with what was written [in Approved Document B].”

‘Approved Document B’ is a government document giving statutory guidance on building regulations in England, covering fire safety matters within and around buildings.

Dr Colwell said she would draft a “frequently asked question” for his approval, setting out that the material was banned. Mr Metcalfe told the inquiry that he expected the FAQ to arrive “within weeks” but it didn’t appear.

One of Dr Colwell’s colleagues at the BRE, Brian Martin, was also noted on his inquiry witness statement as commenting as he left the meeting: “There’s going to be a major fire.”

Minutes recorded at another meeting stated that Mr Metcalfe said that ‘Approved Document B’ was intended to ban the use of combustible cladding due to the phrase “filler material” in the section on insulation. This was meant to be a “catch-all” term, he said, meaning all materials in the external wall should’ve met the standard of limited combustibility.

He said the clause was “poorly written” and “misleading”, but that he was still “content” to follow the government’s interpretation going forward.

The organisation published advice to its members in April 2017, just two months before the blaze at Grenfell, saying that cladding panels should meet the standard of limited combustibility. But there was still no official guidance from government.

“No one thought to…ask themselves the question, well…there’s a ten-year legacy of misunderstanding by the UK construction industry – what are the life safety implications of that?” said Richard Millett QC, counsel to the inquiry.