From small components to the finished building, learning how everything performs in a fire is crucial information for designers, clients and end-users alike.
Good building design in terms of fire safety means it accounts for every aspect of the building - that every wall, ceiling, door and floor has been tested in line with standards and regulations. It is important that every element has enough fire resistance as specified in the standards and regulation to ensure life and building safety. Therefore, every element has to be fire tested in recognised UKAS accredited labs (testing houses) to secure impartiality and achieve the required trust in the product. In a nutshell, fire testing is divided into two main categories – reaction and resistance to fire.
Designing for fire resistance and reaction
Building components and structures are tested in terms of minutes they are resistant to a fire in a laboratory-controlled furnace, when they are subjected to a standard fire curve with regulated pressure and furnace temperature. Three main resistances (load bearing capacity, integrity, and thermal insulation) for the element in a fire resistance test are usually considered depending on the nature of the element and its function in the building. For example, a door is not a load bearing element in a building so that only integrity and thermal insulation will be considered in a door fire resistance test. REI is used to shorten the elements fire resistance test and followed by the achieved time in the test. R signifies the load bearing ability during a fire, the E signifies the integrity and I signifies thermal insulation. It is highly important to understand each fire resistance (REI + achieved time) for each element as required in Approved Document B or BS9999 to ensure fire safety in a building. Having less fire resistance REI in a building for an element than needed one can be life threatening in case of fire since that element will not hold fire for the required period as required.
Reaction to a fire determines the behaviour of every material in a building element or system when exposed to fire. This indicates its combustibility and its role in the spread and development of a fire. Materials are classified based on their combustibility according to BS EN 13501 (European standard) or BS 476 (UK national standard).
For example, according to European standard for reaction to fire classification EN 13501-1, materials are categorised from A (the best as it is non-combustible or very limited combustibility) to F (the worst as it is highly combustible). These categories are defined based on various relatively small-scale fire tests such as non-combustibility test (ISO 1182), bomb calorimeter (Gross Calorific Value test ISO 1716) and so on. It is also important to know the used materials in building elements to achieve compliance to regulations and guidance, or to design an element which can have a great chance of passing a resistance to fire test. For example, it is necessary to have appropriate material fire rating classification for a façade system to comply with Diagram 40 of ADB regarding external surfaces and walls fore surface spread flames.
Since the Grenfell Tower tragedy, fire safety is certainly a topic of focus in the UK. It is important to test every element in a building and ensure its fire resistance and reaction to fire before contemplating it to be in the building design. For instance, if all façade systems have been tested against BS 8414, the chance of having tragedy like Grenfell Tower would have been much lower since the combustibility of ACM cladding and its fire spread would have been identified much earlier.
Principles to follow when testing
It is crucial for architects and building developers to ensure that every element and material to be used in their building has been tested to appropriate standard and achieved all requirements. This must be sought in the design stage, not when the materials and elements are already in the building and then looking for solutions. It is best practice to communicate with the product manufacturer or the supplier about every material and element fire safety requirements before specifying it for a building.
There must be an appropriate testing report and classification report from a recognised UKAS accredited lab for every element resistance to fire. In absence of a testing report, it may be possible to have an assessment in lieu of a fire testing from a UKAS accredited lab with profound knowledge of testing. It is worth it to mention that desktop studies (assessment) for façade systems is not permitted in recent Approve Document B and BS 9414 has been published to make any assessments for façade system.
Special consideration must be made for high-rise buildings as resistance times of building components are always increased the further up the building you go to ensure residents have time to evacuate to safety.
Sometimes it can be a difficult process to review all the elements of the building. We need to look at the coating as well as the structure for some and ask whether these components comply for the specific building. A building beside a national heritage building, for example, must be specially examined to look at how it can resist a fire to save the building next to it.
Testing and assessment is an essential part of the golden thread mentioned in the Hackitt Report. If this is started early, safety will be at the forefront of the design and build programme throughout. Adequate information needs to be available to all stakeholders, with a paper trail according to testers’ guidelines.
If all future decisions are based on appropriate fire testing at foundation level, the building, elements and products will be safe for a lifetime.
This article is based on an interview with Harem Hussein, Fire Safety Engineer at Efectis
Join us at our upcoming event, How fire safety might change construction in the next few years? on the 14th April
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