Historic buildings have particular susceptibility to the dangers of fire. Ingval Maxwell and Paul Chatham draw out some of the key lessons to inform a better strategy
The fire at Cathedrale Notre-Dame de Paris in April 2019 destroyed spire and roof, severely damaging upper walls and puncturing the masonry vaults. Over 400 firefighters were deployed and a human chain carried artwork and objects to safety. Once more, the incident raised questions about the safety of historic structures and what should be considered to preserve them against fire. The costly reconstruction of Notre Dame will be a copy of what previously existed but with diminished historic cultural value.
Fire has always threatened historic buildings. Construction, hot work, portable lighting and variable usage all create different risks. Human factors, lit candles and open fires are also responsible, as are antiquated electrical systems and equipment, vandals and arsonists. The considerable volumes of water used to extinguish fires can also saturate remaining fabric subsequently causing residual damage. Delays in executing repairs or making remnants weatherproof can exacerbate the loss. Devastated structures left open to the elements provide conditions for fungus and decay cycles to take hold.
Building Regulations address life safety and structural integrity, but do not retrospectively apply to listed and historic buildings, except in planning for works to them. However, in addition to safeguard life, consideration should be given to protecting historic fabric and content. A fire strategy should be concerned with both. The nature, significance and value of historic buildings requires a strategic approach including the following factors:
- · Absence of overnight staff or occupants
- · Advance working with the fire and rescue service
- · Alarm systems directly alerting the brigade
- · Availability, reliability and location of water supplies
- · Compartmentation
- · Detection and suppression
- · Evacuation routes
- · Heritage status
- · Insurance considerations
- · Location and possible access restrictions
- · Preventing fire spread
- · Protecting fabric and content
- · Risk assessment methodologies
- · Safe salvage procedures and storage
- · Security considerations
- · Staff training and management
- · Vulnerability during construction and use
It can take as little as three minutes for a room fire to reach a staggering 1,000°C. Fire alarms, installed for life safety, should be regarded minimum level protection. Consequently, owners need to consider in advance the challenging question, ‘What do you want left after your fire?’. Informed professionals need to advise an appropriate answer to the inevitable retort: ‘Everything, but I don’t expect it to happen to me!’.
The answer must reflect on a complex set of interlinked issues to achieve a balanced response. Giving due regard to security, documenting building and contents should best be carried out to inform a Fire Action Plan, which should identify a priority ‘snatch list’ of important contents targeted for early salvage. A sobering thought is that a post-fire ‘archaeological’ survey of charred remains might be the only chance to record the remnant evidence of original historic interiors.
Many historic structures are not fully covered by insurance. Fire prevention personnel should be familiar with principal international heritage charters and conventions to assist informing insurance considerations, intended prevention works, and decisions regarding reconstruction needs. A renewed focus should also be directed towards preventing fire occurring in the first place. Regrettably, due to the way official statistics are reported, it is impossible to obtain accurate figures on the overall loss of historic buildings. But, in England alone, recent data suggests fire accounts for the total loss of one internationally important building each year (grade I) and one nationally important building every four months (grade II*). Additionally, at least 20 empty or derelict listed buildings a year are destroyed.
Fire loss during construction work
Although historic buildings are most vulnerable during construction, the work provides an opportunity to incorporate fire prevention measures if considered during the early design process. Measures to be considered during actual work include:
- · Fire retardant sheeting to scaffolding
- · Installing temporary compartmentation
- · Keeping a tidy site to minimise the potential fire load
- · Maintaining existing compartmentation
- · Managing existing fire detection systems
- · Prohibiting or managing hot works
- · Regular on-site presence and training
- · Safe storage of flammable materials
- · Sequencing work
It is not always obvious how to improve a historic building’s fire protection without creating additional harm to its significance. Compartmentation should not be considered in isolation. While it can delay and reduce fire spread it needs to be effected without restricting natural ventilation which historic buildings depend on to combat condensation. A risk analysis should recognise the:
- · Building fabric and its structural features
- · Fire brigade response time
- · Fire loading and probability of ignition
- · Immediate and prolonged availability of fire-fighting water supplies
- · Length of time to initiate fire fighting
- · Particular vulnerabilities
- · Surroundings and activities
The more fire-fighters know about a building before attending a fire, the greater the chance of it, or significant parts of it, being saved. It is important to provide fire and rescue services with relevant information on all perceived values and site conditions that could influence effective fire-fighting. Crucially, at no time should human life be placed at risk.
Fire protection and suppression technologies
Alongside the basic requirement to implement effective compartmentation and management procedures is a need for greater understanding of traditional and developing protection and suppression system technologies, including: aspirating detection, foam, gas, hypoxic air, infra-red beam detection, manual extinguishers, radio based detection, water misting and sprinklers.
Each system should be appropriately assessed for its intended purpose, recognising that suppression techniques can also provide integrated alarm mechanisms. Regular testing and follow-up system maintenance will be required with any adopted approach.
If considering water sprinkler or misting systems the commonly held, but irrational, view that water can do more damage than fire needs to be put in perspective. The possible effect of either can be a straightforward choice – how realistic is it to reconstruct from a jumble of ‘burnt ash residue’ compared with something that ‘got wet and still remains’?
Misting systems disperse water at two gallons per minute, while each sprinkler head distributes an average of 15-20 gallons per minute. Both introduce significantly less water than a single fire-fighting hose dispensing 100-250 gallons per minute. Sprinklers only operate in the fire’s immediate vicinity and, statistically, over 82% of fires have been controlled by four or fewer activated heads – often extinguishing a blaze before fire service vehicles arrive.
Introducing fire protection technologies into historic and culturally important buildings
Primarily, the insertion of fire detection and suppression systems into culturally important historic buildings should be assessed as being:
- · Essential: Systems should be central to meeting the joint objectives of protecting life, buildings and contents.
- · Appropriate to risk: Installed systems should be empathetic to the considered risk.
- · Compliant with legislation: Systems should be installed according to demonstrable performance-based and other legislatively prescribed safety standards.
- · Minimally invasive: The retrospective fitting of systems should involve minimal degrees of physical intervention on the historic structure.
- · Sensitively integrated: Installed systems should be aesthetically considered and integrated sympathetically with the historic fabric and detail.
- · Reversible: Systems should be installed according to a reversible ‘plug-in/plug-out’ philosophy. Current systems will be superseded in time.
The Notre-Dame incident again raised concern over the loss to historic buildings from the effects of fire. No single solution can be applied to all historic buildings – they are unique and vulnerable in different ways. Many have survived for centuries without encountering fire, yet many others have suffered fire damage and loss. Successfully repaired to continue to serve future purposes, the inevitable loss of original authenticity and significance is regrettable. Greater emphasis put on recording and installing suppression before a fire takes hold at least provides some comfort and solace should an incident occur.
Ingval Maxwell is a member of the RIBA Expert Advisory Group for Conservation; Paul Chatham is Director of Peregrine Bryant Architecture.
Published guidance material on fire loss to the built heritage
There is no shortage of freely available and relevant on-line downloadable guidance and advice aimed at stemming the loss of the built heritage to the effects of fire, including:
This Cooperation in the field of Scientific and Technical Research programme (COST) was a European wide initiative which, through mutual collaboration, aimed to reduce the significant physical and cultural loss of Europe’s built heritage to the damaging effects of fire. Involving a wide range of experts from 20 countries, the Action was achieved in a multi-disciplinary, multi-national manner through the collaboration and integration of a variety of related research and practical projects. The four year programme, initiated in December 2002, concluded with its final report and associated documents being published in 2008.
This work remains the most comprehensive international study of fire loss to historic buildings to date. COST Action C17 Index to Associated Publications. 2008
The proposals within the CFPA guidelines were produced by the Slovenian Fire Protection Association on the basis of many documents and studies, resulting from COST Action C17: Built Heritage: Fire Loss to Historic Buildings. Working group 4 of this programme worked on property management strategies and has produced excellent practice guidelines.