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The dark heart of the cladding scandal has been exposed

30 March 2021

9:09 PM

30 March 2021

9:09 PM

The Grenfell Tower Inquiry has exposed the dark heart of the building safety crisis in recent weeks, as it examined the role of cladding and insulation firms in causing the fire. We have learned that the products used in the tower’s cladding system were known to be severely flammable and that tests pointing this out were suppressed by the manufacturers as they chased lucrative contracts for high rise buildings.

There is no underplaying the size of what has been revealed by this section of the inquiry. This is a monstrous corporate scandal, enabled by failures of some of the construction sector’s most respected institutions. The effects reach far beyond Grenfell, with innocent flat owners currently facing bankruptcy to pay for the removal of these and other products from the walls of their homes.

The primary evidence has involved three companies: Kingspan, an Ireland-based multinational which turned over £2.4bn globally from selling insulated panels in 2020; Celotex, an arm of the French-multinational Saint Gobain and Arconic, an American giant which traces its routes right back to the historic Aluminium Company of America.

It was Arconic which provided the violently combustible cladding panels used on Grenfell Tower (under its Reynobond brand), while Celotex and Kingspan manufactured the plastic insulation fitted to the tower’s walls.

Arconic – we learned – discovered as early as 2004 that if its panels were bent in order to be hung to a building on rails (known as a cassette system) they performed horrendously in fire tests. Configured in this way, the panels burned ten times as fiercely as when they were fixed to a frame with rivets, and emitted seven times as much as heat.

But instead of warning its clients, Arconic said the bent panel test was a ‘rogue result’ and continued to market its product on the basis of the fire-safety grade achieved by the rivetted system. It was the cassette system which was used on Grenfell Tower.

The firm had the capacity to make a far less combustible version of its cladding panel, using lower quantities of polyethylene. It sold these safer panels to clients in countries with tougher regulations such as Germany and Poland. As countries around Europe tightened their cladding regulations, the UK did not, relying instead on a standard called ‘Class 0’ which primarily assessed the spread of flame across the surface of the panel – not its violently combustible core. Due to our more lax restrictions, Arconic sold the pure polyethylene panel as default in the UK market.

It continued to sell these panels despite internally acknowledging that they were dangerous. In 2007, after listening to a speaker describe the risks of the product at an industry event in Norway, the firm’s marketing manager wrote an internal briefing document speculating about the potential for a fire in a high-rise clad with PE panels which ‘kills 60 to 70 people’. The eventual death count at Grenfell Tower was 72.

A senior technical member of its team, Claude Wehrle, who oversaw the testing, also issued a series of strident warnings to his seniors, particularly as large cladding fires began to occur in the Middle East – demonstrating the real-world risk.


In January 2016, following a near miss in Strasbourg, he wrote: ‘We really need to stop proposing PE in architecture. We are in “the know” and it is up to us to be proactive… AT LAST.’

The inquiry was declined the opportunity to learn more about this warning and others because he, along with two other colleagues, refused to attend.

Arconic was helped to access the UK market by a certificate from the British Board of Agrement (BBA) – a highly respected certification body, dating back to the 1960s which called itself the UK’s ‘leading authority on building product certification’. Architects and contractors held it in such high regard they took its certificates at face value. A stamp from the BBA was the ultimate seal of approval in the industry.

But when it came to Arconic, the BBA accepted a £16,500 fee to produce a certificate which bestowed a ‘Class 0’ rating on the polyethylene-cored panels in 2008, despite it only having seen testing to this standard for the fire-retardant version of the product. The BBA relied on Arconic’s 2004 test which used panels bolted to the wall, and did not ask for the results of the cassette test, even though the certificate appeared to cover them.

Then in 2015, after it attempted to get fresh product data from Arconic and was stonewalled for 16 months, the BBA reissued the certificate anyway, based on a simple data check using the company’s website. By this time, Arconic had privately seen its panels fail fire tests several more times, and had formally reduced its classification from Class B to the basement ranking of E. But the BBA – unaware of this – reissued its certificate, erroneously restating the ‘B’ grade.

The firm also issued a certificate for Kingspan’s K15 containing positive comments about its fire performance which the BBA’s chief scientific officer accepted could not be substantiated and were not supported by test data. He denied the firm had been ‘toothless and weak’ in its dealings with these manufacturers.

The story for the insulation manufacturers – who largely gave their evidence before Christmas – was little better. Kingspan, it emerged, had relied on a 2005 test on a system involving its insulation to widely market it for high rises.

But in 2006, it changed the way it made the product and when it retested another system in 2007 the result was – in the words of its own internal report – ‘a raging inferno’. This was never revealed to the market, and Kingspan obtained certificates suggesting its product could safely be used on high rises on the strength of the 2005 test.

When the UK’s biggest private building inspector, the National House Building Council (NHBC) cottoned on to the lack of good test data for the product and threatened to start rejecting it, Kingspan threatened it with action for defamation. The NHBC backed down and would later publish guidance endorsing the use of the product.

The inquiry also exposed how the firm had sought to influence the government’s post-Grenfell response, instructing high-end public relations firms to lobby politicians, wining and dining key MPs and presenting evidence to a select committee which sought to undermine confidence in non-combustible cladding systems. It was a line of investigation which culminated in Richard Millett QC, the forensic and occasionally ferocious barrister who has led the cross-examination, asking if the firm had ‘done its best to ensure that science was secretly perverted for financial gain’, something Kingspan witnesses denied.

Celotex, meanwhile, passed a large-scale test in 2014 which utilised hidden fire resisting boards to help its insulation achieve a pass. The boards used in the test were never declared to the market.

They were also not mentioned in an official report from the Building Research Establishment (BRE). The BRE was once our national research facility before being privatised in 1997. Since then, it has made money commercially, including by running fire tests for Kingspan and Celotex. It was involved in the change to the regulations which made these tests possible.

A key question the inquiry chair Sir Martin Moore-Bick will determine is whether or not BRE staff knew the additional boards were being used. Celotex witnesses claim a senior BRE technician was aware of the use of the panels. He firmly denies this.

Mysteriously, the normal process of individually photographing and cataloguing every component of the test rig before its installation was skipped for this test. The delivery note for the boards could also not be found. The inquiry saw evidence showing the boards were photographed on the completed test rig both before and after the test by BRE staff. But their witnesses say they did not realise what the photographs showed.

This section of the inquiry’s work has now finished but the consequences of what it has exposed are unlikely to be over. There will be calls for criminal sanction, as well as likely civil claims from those who live in or own the thousands of buildings to which these products are still attached.

There also appears to be an urgent need for reform – which extends beyond the narrow world of cladding materials to the entire construction products sector and possibly the whole world of product testing, marketing and certification.

At its core, this evidence has demonstrated the terrible danger of corporate secrecy, especially on matters of life safety. If we are to take seriously what has been revealed, a new era of transparency, accountability and tougher regulation must follow.

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