ROOFING SYSTEMS
Section B4 of Approved Document B (Fire Safety) of the Building Regulations, which relates to roofcoverings, is concerned with the resistance to the spread of fire from an external source, prevention of the spread of fire to adjacent buildings via thermal radiation, and the resistance to flame spread over the roof and/or fire penetration from external sources
Croof, Droof, Eroof, and Froof. Despite this European standard being largely harmonised, the testing process does include specific measures designed to meet the legislative requirements of different countries. As a result, there are four tests that each have slightly different test methods. For example, t4 was introduced to meet the stricter requirements demanded by the UK regulations. It has a two-stage test method incorporating burning brands, wind, and supplementary radiant heat measures. If the system passes the required criteria, it receives Broof (t4) classification. A Broof (t4) classified system is referred to as ‘unrestricted’, or ‘low vulnerability’, and therefore has no minimum distance requirement between adjacent buildings. Anything less
than a system that meets the Broof (t4) classification means that the building or buildings are more susceptible to fire risks.
System approach – no substitutions The substitution of components within a system without the appropriate testing was among the key issues raised in the Hackitt Review. A factor to consider is that fire resistance classifications apply to the whole roof system, rather than individual components. This means that if the system has only been tested and passed with a specific type and thickness of insulation, for example, it is dangerous to assume that it will still perform as expected if the insulation type or thickness differs from that tested. This applies to any of the components that
make up the system. A particular risk is that the substituted components are more combustible than the ones tested, and therefore pose a significant fire risk if installed.
Furthermore, some suppliers may use desktop studies, also known as ‘assessments in lieu of a test’, as a way of claiming compliance without the physical testing. This approach uses previous test data to predict how a system will perform, such as using a system test with a specific thickness of insulation as an indication of performance when a different thickness is used. This has, unfortunately, been used frequently in the industry, and minimising this practice was among the key recommendations of the Hackitt Review.
Alteration to the build-up of the system
A flat roof asset management partner’s first step is to understand the condition of the healthcare estate’s flat roofs, by undertaking a roof condition survey – which will be able to confirm whether any urgent remedial works are necessary, or, conversely, that no immediate works are needed.
70 Health Estate Journal July 2021
Another factor that can affect the performance is an alteration to the build- up of the system. A change in the type of insulation can have a significant impact on the fire performance, and will invalidate any test certification. For example, the tested system may include a mineral wool insulation, which is classified as non-combustible under the Euroclass classification. If this is switched for another type of insulation classified as ‘combustible’, any certification for the tested system no longer applies. In addition, it is important to look at the scenario the system was tested in, and to ensure that it matches where it will be installed. Manufacturers may only test the performance of the system in a limited set of circumstances, which may or may not represent the building in question. For example, in all the tests the system may have been installed on a concrete roof deck – in effect a best-case scenario. When tested on a deck made of a combustible material (such as plywood), it may not perform as well. Reputable suppliers will have tested their systems in a range of configurations and situations.
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