Tower cladding tests after Grenfell fire lack transparency, say experts

Building safety experts have warned that government tests on tower block cladding in the wake of the Grenfell Tower disaster lack transparency and are too simplistic to be used to condemn blocks as unsafe.

Fire risk consultants and architects have suggested the government should reveal what tests were being conducted on the material after it was revealed every single cladding sample sent for analysis had failed the new assessment.

The communities secretary, Sajid Javid, announced on Monday that samples of aluminium panels from all 75 buildings that had been sent for fire retardancy testing had so far “failed”.

But he did not reveal what testing was undertaken apart from to say they determine whether the materials meet “the requirement for limited combustibility in building regulations”.

The Department for Communities and Local Government (DCLG) asked councils to cut samples of at least 25cm x 25cm from the cladding of towers and send them to the Building Research Establishment (BRE) at Watford for testing but has not said if the tests show whether they meet a British standard test.

Councils in Liverpool, London and Plymouth have ordered the removal of panels following the tests and follow-up inspections by fire experts. Camden evacuated residents from four tower blocks over the weekend over fire safety concerns.

It was reported on Monday evening that the same test body that is now assessing cladding samples had advised the government a year ago on their use and had not recommended a change in policy.

Sky News reported that BRE advised DCLG that there was “an increase in the volume of the potentially combustible materials being applied”. The report added that it was advised “there is currently no evidence from these investigations to suggest that the current recommendations [...] are failing in their purpose”.

Experts have warned that far more comprehensive tests on the entire cladding system are needed to establish if buildings are as at-risk as Grenfell was, including the insulation and design details such as fire stops. The shadow housing secretary, John Healey, told the House of Commons that “cladding is not the whole story”.

“The government is fundamentally flawed in its use of the BRE to conduct overly simplistic and limited fire test samples and not the complete cladding assembly,” said Stephen Mackenzie, a fire risk consultant. “The small scale tests on external panels need to to be extended to a full disassembly.”

He said he had observed the removal of panels in three locations, including in Camden, and said he was worried that “we could be pulling off cladding systems that are potentially OK”.

Tens of thousands of people are facing uncertainty over whether they will be able to stay in their homes and hundreds have already been evacuated from the Chalcots estate towers in north London.

Barry Turner, director of technical policy at Local Authority Building Control, which represents council building control officers also asked: “I would like to know just what tests these panels are failing.”

“For any material to undergo a fire test as laid down in BS476 [which grades fire resistance] or one of the EU equivalent standards, you need a specific panel size, it needs to be mounted in a specific way,” he said. “There are fire tests done on individual products, but you need to test them combined [including insulation, cavity and fire stops] to see if they meet performance criteria for the job as a whole. That is how these systems are assessed for compliance with the building regulations.”

One architect responsible for some of the projects where cladding has been ruled to have failed, asked: “What are they testing to what standard? This could be a massively costly and disruptive error to thousands of residents.”

On the Chalcots estate, the assembly is said to have been designed with the approval of building control and has been tested in two real fires, the latest in 2012, in which the fire did not spread beyond a single flat. This could have been because of the way the panels were combined with non-combustible mineral fibre insulation, fire breaks. Cutting off and testing a piece of the aluminium cladding would not tell the government’s testers anything about that wider context.

In Bootle, where two blocks had their cladding removed, the housing provider One Vision said: “Test results have shown certain elements of the cladding on two of our high-rise blocks, Cygnet House and Wren House, whilst meeting building regulations, does not meet the latest Department for Communities & Local Government test criteria.”

The London Borough of Hounslow, where the Clements Court tower failed the DCLG test, panels are being “swiftly” removed, but the council stressed: “The insulation material behind this outer cladding is a ‘rockwool’ material which is a non-combustible product, unlike the case of the Grenfell Tower, where the insulation was a combustible type.

“The system at Clements Court also differs from that at Grenfell Tower in so far as there was no interference with the interior of the building as part of the installation.”

A spokesman for DCLG said the tests are on “core materials in aluminium composite material cladding samples” and have been “agreed by a panel of independent experts, who judge that a test failure means that the cladding does not meet the requirements for limited combustibility in current building regulations”.

The combustibility test has three categories and cladding in category two or three fails the building regulations’ limited combustibility requirement according to the DCLG.