Government proposals to limit the use of desktop assessments to test the fire performance of external cladding systems could actually increase their use and potentially lead to dangerous materials being installed on buildings
Dame Judith Hackitt’s interim report from her review of Building Regulations and fire safety called on the government to “significantly restrict” the use of assessments in lieu of a fire test – desktop studies – to approve changes to cladding and other systems, and ensure they are only used “where appropriate and with sufficient, relevant test evidence”.
In many cases, there are standards which provide rules for assessments in relation to specific tests and products, known as standards for extended application.
A government consultation is proposing that where a relevant standard for extended application exists, this should be followed. Where there is no standard, then the principles of BS EN 15725:2010, a European standard on how to carry out extended application reports on the fire performance of construction products and building elements, should be followed.
However, risk management firm FM Global warned that the proposals do not address “fundamental issues” with the accuracy of fire tests and would send a signal to the industry that desktop assessments for ACM cladding are acceptable and could encourage their use.
It added there is “strong evidence” to suggest desktop studies have contributed to the use of dangerous combinations of building materials. Of 319 public buildings identified by the government with ACM cladding in the wake of the Grenfell Tower fire, only 13 had cladding systems that meet safety standards.
FM Global said the increase in the use of desktop assessments for ACM cladding systems is the “primary factor” in explaining why so many buildings failed safety tests.
“We simply do not have enough data from actual fire tests to know if the desktop assessments are reflecting how these materials would behave in a fire. Therefore, we have no confidence in them. The government proposals will not change the data that desktop assessments are based on and we are concerned they would, in fact, contribute to their wider use,” said Chris Johnson, executive vice-president of FM Global.
“Testing for ACM cladding needs to be vigorous to avoid any more disasters like Grenfell. Only through scientifically-based testing will we be able to develop the knowledge base and experience to fully assess the materials and whether they are fit for purpose. Without a sufficient knowledge base and detailed understanding of all the variables, relying on desktop assessments for cladding systems is like building on sand.”
The government consultation runs until 25 May. Ministers are expected to issue a response to submissions later this year.