Initial results from the first set of large-scale cladding combination tests have been released, showing 82 buildings have the cladding combination which has failed the test.
Following the publication of the results, the government announced an independent review of building regulations and fire safety. Led by EFF chair Dame Judith Hackitt, it will look at current building regulations and fire safety with a particular focus on high rise residential buildings, including examining compliance, enforcement, and management. It will report jointly to the communities secretary Sajid Javid and the home secretary Amber Rudd.
Immediately following the tragic fire at Grenfell Tower on 14 June, tests were carried out on samples of aluminium composite material (ACM) cladding from local authority buildings across the country. The tests, which followed the first of four routes to fire safety compliance as set out in the Building Regulations 2010, found that all cladding samples failed the flammability requirements. They were carried out by the Building Research Establishment (BRE) near Watford.
For this test, which complies with government guidance in Approved Document B, cladding samples were burnt in a pure oxygen atmosphere, determining the gross heat of combustion. The samples were then rated one to three, with only a grade one indicating a pass.
But the latest, large-scale test follows criteria set out in BS 8414-1. Rather than testing a sample of cladding, an entire 9m high cladding system in built and then burnt to test how fire spreads across the surface.
To fail the test, external or internal fire spread must climb above a certain temperature within the first 15 minutes of the test starting. In this case, the test had to be stopped after eight minutes and 45 seconds.
BRE test results
Source: BRE / DCLG
Three common types of cladding are being tested with two types of insulation, making six test combinations.
This first set of results tested a cladding system combining an ACM panel containing an unmodified polyethylene core, and insulation material made from a rigid polyisocyanurate foam. An expert panel has advised the government that the result means the system does not meet building regulations.
The other two ACM panel types use filler materials of fire retardant polyethylene, and limited combustibility mineral, while the second type of insulation is non-combustible mineral wool. Test results have not been released yet for these combinations.
So what does the industry make of the results?
New Civil Engineer technical editor emeritus Dave Parker said that, as was predictable, the ACM panels with their flammable cores were partially destroyed in the test. It is worth noting that the manufacturer does not recommend this version for this application.
The test also showed there was no significant horizontal spread of flame over the external face of the ACM. The rigid polyisocyanurate (PIR) foam insulation also appeared to perform as claimed by the manufacturer. There was surface charring, but no ignition and no surface spread of flame.
“To mind it is more of a realistic test, a more representative test,” said Hilti fire engineer Alastair Brockett.
“But if they’ve carried out a series of these tests and it’s still showing failure, the question then has to be asked: is it just the material? Or is it the form of assembly? Is it the type of construction? Is it a combination of these which is causing the problem? And that then asks a much, much bigger question in terms of, is this whole concept of over-cladding buildings – in the way that we’ve been doing it – fit for purpose?”
“It’s certainly a cause for concern,” added Local Authority Building Control director of technical policy Barry Turner.
“We’ve ended up with a material, or we’ve ended up with buildings that have now been proved to be unsatisfactory. The next question is: why?”
According to Mosen managing director Fathi Tarada, the results reinforce the need for ensuring fire risk assessments are of the highest standards for tall buildings, something which New Civil Engineer has been calling for.
“It’s likely that the combustible panels were just one of several fire hazards that, in combination, led to the Grenfell disaster,” he said. “The other factors may include insufficient fire breaks within the cladding and between the cladding and the window frames, the presence of gas pipes and the advice to stay within the flats in case of a fire (all issues that the public inquiry will no doubt consider).
“It follows that other towers may not necessarily be exposed to the same level of risk, because the other factors may not be present. That’s why a proper fire risk assessment is crucial in these cases.”