Select Committee on Transport, Local Government and the Regions Memoranda


Memorandum by Association for Specialist Fire Protection (TAB 06)

  We note with interest your press notice announcing the above enquiry and would like to make the following comments with particular regard to your interest in the sustainability of tall buildings, their construction and long term flexibility of use. These comments concern the essential requirement of fire stability and some aspects are considered in the light of the events of 11 September at the Twin Towers in New York.

UK BUILDING REGULATIONS

  In the UK we have excellent guidance on the requirement for fire safety in buildings set out in Approved Document B (ADB) of the Building Regulations. This guidance recognises the fact that fire is a serious risk in all buildings and suggests that these be constructed to have certain periods of stability in a cellulosic fire. For tall buildings (ie over 30 M height) the period of structural stability is two hours. This period of time also applies to the integrity and insulation of certain compartments of the building such as the fire fighting shafts but the actual corridors in other parts of the building are limited to 30 minutes protection in many cases.

  We feel that the enquiry may wish to consider if this level of protection is adequate in two respects. Firstly the question of the severity of the fire and secondly the integrity and insulation time periods where these are limited to 30 minutes. Materials and systems that are capable of providing longer periods of stability, integrity and insulation are available both for cellulosic fire and, for that matter for hydrocarbon fire where temperatures would be considerably higher.

  The owners of certain tall buildings in London have been looking at this question and costings show that to upgrade to hydrocarbon fire materials is likely to add between one and two per cent to the cost of a building. Upgrading to longer periods of cellulosic fire as were recommended in the Approved Document prior to 1991 would, in all probability add well under 1 per cent to building cost as the materials concerned in many cases could be fixed with similar labour costs.

  As the materials and systems are readily available we feel that the enquiry should consider if some upgrading of the recommendations is necessary in the light of the risks of major loss of life in a fire at mid height of a tall building.

COMPARTMENTATION

  Fires almost always start small and if the spread can be limited the effects can be controlled. ADB works on the principle that buildings should be divided into areas of manageable risk and that the walls should have stated periods of resistance to fire in terms of stability, integrity and insulation. The objective is to keep the fire in the compartment of origin. Even if the enquiry forms the opinion that existing recommendations are sufficient it is vitally important that the work to create these compartments is properly carried out.

  There is evidence from an on-going research exercise entitled "Ensuring Best Practice for Passive Fire Protection in Buildings" sponsored by the DTI (formerly DETR) that poor installation of compartmentation measures is endemic in the construction industry. The research for this project is being conducted jointly by the Fire Research section of the Building Research Establishment and the Warrington Fire Research Station both as partners with the ASFP. In the event of a fire in a tall building, poorly installed measures will greatly increase the risk to occupants as well as fire fighters through the premature spread of smoke and flames from the seat of the fire. It is our opinion that such an event will take place in a tall building where there will be considerable public injury and/or loss of life that extends way beyond the expectations of the authorities.

  The enquiry may wish to consider ways in which the authorities may be sure that such measures as are proposed in ADB and included in the design have in fact been adequately carried out. The industry has Accreditation Schemes available for the installers and the use of such schemes is another recommendation in ADB and at present this has a limited but growing voluntary take up by property owners. Under these schemes the installer has his work inspected and his procedures audited on a regular basis and issues a "Certificate of Conformity" for the work on completion. It would be simple for the regulatory authority to require such a certificate for all fire protection work and this would provide an audit trail for both workmanship and materials to ensure compliance with the approved design.

OCCUPIERS RESPONSIBILITY

  The Workplace Regulations as amended in 1999 require all occupiers to undertake a risk assessment and to maintain this is in an up to date manner. This applies even where a Fire Certificate exists for the building. In a survey carried out earlier this year by the Chief and Assistant Chief Fire Officers Association (CACFOA) as many as 40 per cent of building occupiers were unaware of their duty in this matter and a larger percentage had not undertaken the work. It is a fact, confirmed again by the "Best Practice" research mentioned above that the retrospective fitting of additional services within a building often breaches compartment walls and damages structural protection. Such breaches will increase the risk of fire spread or serious damage and should be picked up by the occupiers risk assessment.

If we have poorly installed measures allied to subsequent damage the risks increase greatly and the enquiry may wish to consider ways in which the duties of the "Responsible Person" as defined by the Workplace Regulations may be more vigorously enforced. Figures published by a section of the new DTLR Fire and Safety Directorate show that although there are over a million employers to whom these regulations apply, only 68.000 copies of the guidance for these employers had been sold by May of this year.

FIRE ENGINEERED DESIGNS

  The Guidance contained in ADB also permits the developer to offer methods of fire protection that are not as suggested in the guidance documents but are the subject of a Fire Engineers design and calculations. This is permitted for either the whole of the design, as would be appropriate for a complex building such as an airport terminal, or for parts of the building where a non standard solution may be required. When such designs are submitted the regulatory authorities would seek proof that the performance will be at least equal to the suggested methods form the Approved Document.

  When considering the sustainability of the building and the long term flexibility in use this can have considerable restrictions. The design proposals contained in BS 7974 Application of Fire Safety Engineering Principles to the Design of Buildings, Code of Practice ask the practitioner to make certain stipulations regarding such things as the fire load, occupation levels, floor loadings and so on. These factors are then applied to areas of the building such as escape routes and calculations done to provide elements of the design.

  Similarly, structural engineers have many detailed computer based calculation methods by which they prove that because of the nature of a design and the loadings likely to be applied to the building in use, then a lower level of stability may be applied than would otherwise be the case. Also guidance in the Steel Construction Institutes document P288 shows how secondary beams within a building may not require added fire protection as would be required by the recommendations in ADB. One of the stipulations in this latter case is that compartment walls must coincide with the primary beams and may not be built over secondary beams.

  When a limit state design of this type is used in a building the decisions taken provide the level of fire protection required only so long as the loadings, positioning of escape routes and compartment walls and other factors for the original building remain the same in practical use. If the purpose of the building changes, if the number of employees increases, if the work done alters or any other material change takes place, then the design may be invalid. A difficulty in such circumstances would be that the new occupier of such a building may not be aware of the constraints. Even new management of the same company may not understand the significance of changes.

  Such designs are often used to keep initial costs within the required budget and may make excellent sense to the original occupier of a building but the long term sustainability may be compromised and the additional work required to bring the structure up to the required standard for any changes in occupancy or use could be extremely expensive when retrospective fitting is required. The enquiry may wish to consider the appropriateness of limit state engineering of this type in buildings that are otherwise very adaptable.

THE FIRE PERFORMANCE OF CONCRETE

  The time taken from the inception of a project to the profitable occupation of a building is critical for the developer and so the construction industry is constantly finding ways to speed up the process of delivery. One well established construction material that has been subject to much change in this way is concrete when used either as the floor slab of a building or when cast into beams, columns or shapes required. Various admixtures are now used to speed up the handling and drying of the concrete and high strength versions are often used.

  With this background it was interesting to learn of a test in a modern concrete structure at the premises of the Building Research Establishment at Cardington on 26 September. The test involved establishing a compartment in the test building and creating a fire intended to represent a one-hour cellulosic fire. At the time of writing this memorandum the official report has not been published and so it is not possible to comment on the conclusions.

  Evidence from other fires, for example the Channel Tunnel fire and experimental work in the American Standards and Test Authority suggest that high strength concrete and other dense concretes can be subject to extensive explosive spalling. Such spalling not only weakens the structure but can be very dangerous to the fire fighter. Where it has occurred repair is expensive and can be complex.

  The enquiry may wish to seek the results of the test on 26 September and consider the opinion of fire experts into the performance of concrete when used in modern tall buildings.

CONCLUSION

  The regulatory background for the construction of buildings in the UK is excellent but the dangers of non-compliance are growing as we attempt to reduce the regulatory burden. The dangers of fire were tragically seen on 11 September and whilst we had exceptional circumstances in that particular event we can see the potential for disaster when fire breaks out in a tall building. It is our opinion as the leading trade body in the fire protection of structures that we are in danger of loosing hard won ground in fire safety as we have tried to illustrate above.

  The industry offers systems of self regulation but only the more enlightened property owners utilize them fully. Insurance costs will rise considerably and the dangers seen in our recent research indicate that further losses are likely due to lower than acceptable standards in some buildings. We recommend more vigorous application of the present regulations for the construction of new buildings, their maintenance during occupation and the suitability of innovative methods and materials.

  We also feel that there are inherent dangers in recent limit state engineering design that will restrict adaptability in the future. We should take great care not to allow short-term gains as were seen in the 1960s lead to long term problems.

  Tall buildings offer greater dangers in fire and the control of their construction and use is critical to public safety. The fire protection industry can provide whatever levels of fire protection society requires but we must not cut corners as this can lead to disaster.


 
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