The British system for fire testing building materials is utterly inadequate and underestimates the ferocity and spread of real blazes, a study commissioned after the Grenfell Tower disaster has claimed.
Full-scale laboratory tests of the combustibility of walls have been essential in assessing whether cladding on hundreds of highrises meet fire regulations after the blaze in west London that killed 71 people.
But they fail to reflect how materials burn in the real world, according to a highly critical report published on Wednesday by the Association of British Insurers (ABI).
It also alleges some manufacturers have been gaming the tests by reinforcing their systems in the laboratory in a way that would not happen in reality, for example using rivets to stop flaming panels falling off as happened at Grenfell.
The government is using the test to determine whether tens of thousands of people are living in blocks facing a similar danger to Grenfell. If correct, the ABI’s claims could mean buildings with supposedly less-risky cladding than the 306 which have so far failed could also burn more dangerously than laboratory results suggest.
The insurers commissioned experts from the Fire Protection Association to conduct their own experiments that revealed that if apartments contain plastic appliances and furniture, and builders have left gaps in cladding or installed bathroom or kitchen vents, a building is significantly more flammable than the British Standards Institution test BS8414 shows.
With plastic added, fires burned 100C hotter than in lab tests based just on wood fire and when gaps in the cladding system were included flames spread across the whole six-metre height of the test rig rather than 1.5 metres when it was sealed.
Huw Evans, the director general of the ABI, said the building control system was now “broken”.
He added: “This latest research is yet more evidence that fundamental reform is needed to keep our homes and commercial premises safe from fire. It is a matter of urgency that we create the right testing regime that properly replicates real world conditions and keeps pace with building innovation and modern design.”
The current testing regime “may not give designers, specifiers or insurers confidence that cladding systems tested to it will ensure the level of building fire safety that is currently inferred by its use”, said the ABI.
The tests have been used to determine whether some materials with limited combustiblity can be used in cladding systems and still meet building regulations. The ABI’s findings will increase pressure on ministers to ban the use of combustible materials on buildings altogether when they respond to Dame Judith Hackitt’s independent review of building regulations which is to report within weeks.
Nine in 10 UK adults now want all new highrise and high-risk buildings to be clad and insulated only in noncombustible materials and want sprinklers to be required, according to a poll released on Tuesday night paid for by Rockwool, which manufacturers non-combustible insulation.
The Building Research Establishment, which is paid by materials manufacturers to conduct the tests at its laboratory in Watford, denied there was “any negotiation or any scope for change or modification to these methods by the manufacturer”.
But Lord Porter, the chair of the Local Government Association, which represents councils across England, some of which are struggling with how to reclad 45 highrises that use Grenfell-style cladding, said: “Using non-combustible material only would provide clarity to all types of landlords who remain unsure about what they should use to re-clad and insulate their buildings. The tragedy at Grenfell Tower must never be allowed to happen again.”
The ABI report suggests the government should stop using the tests to confirm the fire performance of systems already installed on buildings.
The BS8414 test is overseen by the BSI, a private company appointed by the government as the national standards body. The panel that drew up the rules for the test include representatives from the plastic foam insulation industry. The BRE, which carries out the tests, is the former government building research station that was privatised in 1997.
The BSI said: “As with any feedback we receive on a standard, we take it seriously and arrange for the respective committee to review it.” But it warned that any change to the standard would take up to 18 months.
BRE said it was “not aware of any cladding system tested to BS 8414 that has performed poorly in a real fire”. It added: “We remain open to new technical evidence and robust data that supports improved safety – keeping people safe is our key priority.”