Keep your fire classification compliant with building regulations and consider a durable flat-roof specification to resist the spread of fire, says Daren Fraser.
The government has published its draft building safety bill (July, 2020) – incorporating elements from Dame Judith Hackitt’s Independent Review of Building Regulations and Fire Safety – to focus predominantly on building safety standards. The bill seeks to empower the building safety regulator to take action when parties breach compliance of building regulations.
Understanding Approved Document B
Approved Document B (Fire Safety) of the building regulations is a vital reference document and should be used for guidance to mitigate fire risks in all areas of a building.
Section B4 ‘External Fire Spread’ focuses specifically on “resisting fire spread from one building to another” and details the associated hazards. One risk is that airborne material or heat from a nearby fire may cause a roof to ignite. To improve safety, Approved Document B (Edition 2019) states the minimum distances between buildings and the required fire resistance of building materials based on this distance.
The external fire performance of a roofing material can be identified by European classification test standards BS EN13501-5, which classify roof systems into five categories based on their performance:
Broof is the highest fire-resistant rating.
Further to this, testing is carried out to meet individual legislative requirements for each country – t1 for Germany, t2 for Scandinavia, t3 for France, and t4 for the UK.
The specified test for the UK has two stages designed to meet the stricter requirements demanded by UK regulations. 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.
Whereas specific guidance in relation to different building types might provide an opportunity to specify a roofing system with a lower fire rating than Broof(t4), this is not recommended.
The distances stated in the regulations are designed to protect the roof and building from the risk of fire spreading from other structures, but do not account for any other ignition sources that may be closer to the building. Anything less than a system that meets the Broof(t4) classification means that the building or buildings are more susceptible to fire risks.
Another 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 it will still perform as expected if the insulation type or thickness differs from that tested. This applies to any component in the system.
A particular risk is that substituted components are more combustible than the ones tested.
Once a system has been specified for a new or refurbishment project, facilities managers can review the considered solution’s safety and compliance through documentation supplied by the manufacturer/supplier. This should include details of independent certification, such as BBA certification, or a fire test certificate through the fire testing organisation. These will detail whether the system has Broof(t4) classification and whether the components specified match those detailed within the independent certification. If not, it may mean the system is not compliant with current building regulations.
Fire safety is a crucial consideration when selecting a flat-roof system. Specifications incorporating components that have been fully tested as part of a system will guarantee peace of mind that the flat-roof solution is safe and compliant.
Download Langley Waterproofing’s Broof(t4) Compliance: Fire Penetration Performance and Spread of Flame white paper at tinyurl.com/y6pjsfe5
Daren Fraser is head of technical at Langley Waterproofing Systems Ltd