Building systems such as suspended ceilings can play a key part in limiting the spread of fire in a building. But as Rob Gardiner points out, it is important to distinguish between standards relating to reaction to fire and those for fire resistance.
Should a building catch fire, the people within will need to get out as quickly as possible, and the structure needs to remain sufficiently sound to allow firefighters in. Preventing the spread of fire is therefore critical.
Approved Document B provides guidance on the level of fire performance necessary to comply with the fire safety requirements of the UK building regulations. Stemming from the government’s wish to reduce the number of fires and limit the consequences of fire, particularly in residential buildings, in July the Office of the Deputy Prime Minister issued a revised version of the document for consultation. The most obvious change is the way it differentiates between dwellings and other building types: the first part addresses ‘dwellings’, while the second part concerns ‘buildings other than dwellings’. The new document also offers improved guidance on means of escape for disabled people.
School buildings are also the subject of current informed debate. It is proposed that guidance for educational premises will be given by cross-referencing these recommendations with Building Bulletin 100, New Fire Safety Guidance for Schools, which the Department for Education and Skills has issued for consultation. This bulletin places a greater emphasis on property protection than the basic requirements set out in Approved Document B, to ensure minimal disruption to children’s education as a result of a fire.
The deadlines for responses to the consultation documents have now passed and the final version of the new Approved Document B is expected to be published in October 2006 – with the expectation that it will be integrated into legislation in April 2007. In the building regulations, fire protection systems are categorised as either active or passive. Familiar measures such as automated detectors and sprinklers fall into the active category. Less obvious, but equally important, are the passive methods of fire protection that are created by the use of suitably tested materials and construction. These are essential in limiting the development of a fire and in protecting a building’s structure.
Structural components and building materials form an important part of a building’s passive fire protection systems. Suspended ceilings, for example, contribute towards the protection of the building in two ways.
The first is in terms of a material’s fire reaction to fire performance. Requirement B2 of Approved Document B demands that all interior linings within a building – including suspended ceilings – must “adequately resist the spread of flame over their surfaces.” It further states that if those materials are ignited, they should have a rate of heat release or a rate of fire growth “which is reasonable in the circumstances.”
In order to be sure that building components are able to fulfil these requirements, there are appropriate British Standards. For suspended ceilings these have historically been BS 476. However things are set to change.
Part B of the UK Building Regulations was amended in 2002 to include European test methods for fire reaction and fire resistance. So the British Standard and the harmonised European standards can currently be used to show compliance to the Building Regulations. But as part of the process of technical harmonisation of standards within Europe, the new suspended ceilings product standard, BS EN 13964, was published in 2004 and only refers to European test methods. This leads the way for the CE marking of suspended ceilings and the eventual withdrawal of the parts of BS 476 test standards which relate to the fire reaction of suspended ceilings. When this happens, it means that BS 476 testing methods for the fire reaction of suspended ceilings will no longer be acceptable.
However, whether fire reaction testing is carried out to BS 476 or to the new European standards, there are similar concepts involved. These include the ignitability or spread of flame across the surface of the tile and the rate of heat release or combustibility of the product. The European test methods also introduce tests for smoke and flaming droplets, although Approved Document B does not currently give detailed guidance on these.
As European fire reaction test methods have been synchronised, all member states must accept them as the method of showing compliance to their national regulations, although performance levels required to those tests may vary from state to state.
Meeting the above criteria for fire reaction will limit the time taken for a fire to grow. However, once a fire has fully developed, the emphasis moves to fire resistance.
Fire Resistance
This falls under the remit of Requirement B3 of Approved Document B, which states that “the building shall be designed and constructed so that, in the event of a fire, its stability will be maintained for a reasonable period.” Fire resistance is therefore concerned with the protection of the building’s structure and should enable people to get out, and fire fighters to get in safely.
Whereas all suspended ceilings require the appropriate fire reaction performance, not all will be required to provide fire resistance. However, when they are used for fire resistance, the choice of grid system and method of installation are key. So a ceiling tile alone cannot be CE marked as a ‘fire resistant tile’. But suspended ceilings can be used to protect various types of floor constructions, such as mezzanine or timber, and provide effective protection to load-bearing steel beams, provided that they have been installed as tested.
As with fire reaction, there are European test standards for fire resistance. But as yet, there is no consensus within member states on a single test method that is acceptable to all. So either the British Standard tests for fire resistance, or those European tests permitted in Approved Document B, can be used to prove fire resistance performance to the UK Building Regulations requirements.
Although there are limitations to the fire resistance performance that suspended ceilings can provide, there are plenty of other construction techniques and structures that will ensure the integrity of the building. When it comes to fire reaction, however, suspended ceilings can provide very high levels of performance which satisfies the Building Regulations – provided they are tested to the required European or British standards.
Rob Gardiner is technical sales manager, UK and ROI, at Armstrong World Industries.
