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.
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.
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
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
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 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
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.
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.