Fire Threat to Stones of Historic and Cultural Heritage Buildings

Many historic buildings are made with stone structures. In addition to the various benefits that this type of material, which is diversified by composition, aggregation and geometry according to historical periods and geographical areas, it must be remembered that exposure to fire constitutes in most cases an important vulnerability. Even recently, several cases of fire have highlighted the importance of designing from fire, in buildings belonging to the cultural heritage, building elements to which adequate attention is not always paid.

Plan and section of the Guarini Chapel in Turin, where the Holy Shroud is kept. The Chapel has been severely damaged by the fire on April 11, 1997.
Plan and section of the Guarini Chapel in Turin, where the Holy Shroud is kept. The Chapel has been severely damaged by the fire on April 11, 1997. Two thirds of its marble structural stones were damaged by the heat. he complex structure of the dome of the Chapel of the Holy Shroud, severely damaged by the fire of 1997, that was rebuilt using stones taken from a quarry opened for the occasion. The opening of the new quarry was due to the need to replace the numerous stone elements destroyed by the effects of the fire or no longer able to perform their load-bearing function. (image from Wikipedia

The case of the fire that seriously damaged the chapel that housed the Holy Shroud in Turin, on April 11, 1997, can be considered iconic in this regard. For its restoration it was necessary to open the quarry near the place from which at the time the stone material with which the supporting structures had been made had been extracted (see reference, page 25) . Among other things, the individual blocks had been designed and installed with techniques of which the memory had been lost and which forced the restorers to a specific study.

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Cultural Heritage Fire Safety Standards – Italy

The effects of the fire that on 29 January 1996 destroyed the Gran Teatro della Fenice in Venice (Italy), The fire, that threatened also the surrounding historical buildings, is iconic of the vulnerability of the Cultural Heritage buildings and built environments (image: Wikipedia)


In order to understand how cultural heritage fire safety is addressed in the world, a series of posts will describe legislations of different countries. The first post, published with the Author’s permission, is the updated version of a paper presented during the international conference  “Toward a Safer World”  – ESREL 2001. The paper illustrates the Italian rules concerning fire safety of cultural heritage: Stefano Marsella – Performance-based codes vs prescriptive rules: the case of the application to fire protection of cultural heritage in Italy.

According to the EU Construction Product Directive, fire protection of buildings can be designed using either performance based approach (engineering methods) or prescriptive rules. In his work, the Author describes as the application to historical buildings is carried out in Italy, showing the main problems which arise with the use of prescriptive rules in a context extremely rich and complex as italian heritage and showing how, in an fire engineering approach, the special task to protect heritage and the people could be addressed.

When engineers approach the protection of cultural heritage and, at the same time, try to safeguard human life letting people to use and enjoy buildings, the main problems they have to face in the most of historical building lie in the difficulty to meet the mandatory prescriptions. The utmost variety of architectural solution, urban situation and fire load, together with the severe needs of conservation, makes it quite difficult, if not impossible at all, to follow prescriptive rules, which will soon become not acceptable. Regarding this point, we must consider that, in Italy as well as in other countries, fire protection is carried out with a series of rules, prescriptions and standards which were been defined having as a goal new constructions and new building elements. Moreover, hygiene and occupational workplace safety rules must be enforced without any regard to the age or the historical value of the building. Another matter that has to be addressed in the upgrading of heritage to standards of safety is connected to the accessibility requirements of urban environment, matter that the ageing of population and the growing consciousness of people make a primary issue even in solving the fire evacuation problems.

In the following analysis, the Author will examine only the fire protection rules, but is intended that the problems which arise in applying fire protection rules to heritage are quite similar to the ones which accessibility and workplace hygiene and safety bring.
Looking at the problem from another point o view, it must be stressed that the authorities have to face the need to allow the public into these buildings, for political reasons, but also for the need to raise funds for their upkeep. Generally the owners, public or private, have a vested interest in preserving their property and content and should take the matter seriously enough if a definite set of rules would exist, even we must consider that exist a different challenge if the public are to be brought in. In Italy there not exists a national building regulation, neither common prescriptions for public safety, and the only prescriptions that could be used are the fire prevention standards for cinemas, theatres and dancings. So, in the case of public let in a heritage building, the primary interest in protecting people has to face the difficulty to meet a group of rules that were set specifically for buildings built to  receive a great amount  of persons.

Probably, the only reasonable approach to the problem of protecting the heritage lies in the use of a non prescriptive approach, in a framework of performance based rules which simultaneously fix the need to be satisfied with reference to accessibility, public safety and workplace safety.
In the following consideration no reference will be done to cost analysis, for the lack of data in Italy about this issue make it impossible a serious evaluation of the impact this issue on the definition of fire prevention strategies applied to cultural buildings.

1.    Cultural Heritage Safety in Italy
The problem of protecting against fire italian heritage is a main issue in the policy of safety. The worst fires occurred recently in Italy, in fact, have hit mainly important historical or cultural buildings (Teatro la Fenice – Venezia, Cappella guariniana – Sacra Sindone – Torino, Teatro Petruzzelli – Bari).
Starting from the definition of heritage, according Italian laws, may be considered historically relevant any building older than 50. In Italian heritage there are at least 95.000 monuments and churches, 30.000 historical buildings, 3.500 museums, 2.000 archeological sites and 900 theaters. In these figures we must consider that entire town centers, if not entire towns are part of the heritage, with all the risks that technological improvements bring in a so bound environment. Moreover, the most of churches and interesting buildings date back to the last ten centuries, with a great difference of construction materials, structures, content, state of conservation and use. The only amount of libraries scaffolding is several thousand km and, this statement, lets the possibility to remember that bounds don’t exist only in the works to be done inside the buildings, but also in the extinguishing substances that can be used.

2.    Italian rules on the heritage
The common challenge to the authorities, when the problem of fire protection of heritage is addressed is three‑fold:

  • to preserve the building and content from the effects of fire,
  • to protect life (includes fire-fighters) from fire.
  • to limit the impact of fire precautions on building fabric.

If it is clear that in the most of cases something needs to be done, the challenge is on what standard and by what principles should the fire precautions be based. We know that would not be appropriate to apply current standards to historic buildings.
In Italy, common buildings where people work are subject to the rules concerning their accessibility, their hygiene and health conditions and their fire protection features. With regard to such arguments, we may say that a lot of laws, regulations and codes have been enforced by Public Authorities which  concern design, construction stages and maintenance management. Moreover, if the building is considered as a part of the cultural heritage, there exist special laws which will make it extremely difficult to modify the building itself, even if in the case of works intended to preserve it. An important issue to be taken into account, is that, as a general rule, the level of safety and accessibility that laws ask must be assured in every case, so it is not possible to accept in any kind of building, say the historical or artistical heritage building, lower safety and accessibility standards.
Focusing on fire protection (which, nonetheless, is strictly bound to some accessibility prescriptions as well as to the occupational safety), in Italy there exist two prescriptive codes, which are applied in the case of historical building used as places of assembly and as archives. In both cases, emphasis has been given to the human safety, specially in order to means of egress characteristics.
May be useful to add that in Italy the specific activity of fire prevention and fire extinguishing is passed on the National Fire Department, coming from Department of Internal Affairs (Ministero dell’Interno), organised into Brigades by Province, while preservation of historic buildings (public or private owned) is bound by the Board of Architectural and Environmental Heritage (Sovrintendenza ai Beni Artistici e Ambientali).
Until now, we may say that prescriptions for fire prevention have been issued from the new building experiences having, as unique goal, people safety, but nowadays is stronger the common perception that for historic heritage the safety of inhabitants should be reconciled with the need of safeguarding historical and architectural value of buildings as well as goods contained within them.
Looking at the procedures needed to achieve the prescript level of fire safety, it must be said that a list of activities, which are subjected to periodic surveillance, is specified in a Decree of 1982. The only case where the building itself is subject to fire safety control independently from the activity held is the case of heritage buildings. Nonetheless, the control for these buildings hasn’t been in the past so strict as necessary, due to the reluctance of many Boards of Architectural and Environmental Heritage to accept the minimum required safety features and the inherent difficulty to define such features.
For any heritage building, the following obligations are established:

  • acquisition of preliminary approval, on behalf of the territorial qualified Provincial Fire Department Brigade, for rehabilitation works, including normative adaptation and changes in purpose of use;
  • acquisition of the ”fire prevention certificate” following on‑site inspection by the provincial fire Department Brigade, after the completion of the works.

In general, the aim of fire prevention rules, prescriptions and standards issued for different activities or workplaces looks at providing operators with an instrument unequivocally applicable in all cases. Designers must observe rigid bounds, which sometimes are too hard and difficult to be respected so that they are often compelled to ask for derogation through a trade off among Customer, and local Fire Department Brigade. In the case of cultural heritage has become immediately clear that it was impossible to issue fire protection standards. Too many differences and too many bounds made it impossible asking even low impact prescriptions. In order to safeguard building conservation and to assure at least safety of human life, the relevant Ministry issued two historical building oriented decrees:

  • D.M. n. 569, issued on May 20,1992, “Regolamento concernente norme di sicurezza antincendio per gli edifici storici e artistici destinati a musei, gallerie, esposizioni e mostre” (Regulation concerning fire safety norms for historical and artistic buildings destined as museums, galleries, exposition centres, and shows)
  • D.P.R. n. 418, issued on June 30,1995, “Regolamento concernente norme di sicurezza antincendio per gli edifici di interesse storico‑artistico destinati a biblioteche ed archivi” (Regulation concerning fire safety norms for historical-artistic buildings destined as libraries and archives).

Reading such rules it becomes clear that, perhaps violating the general rule that oblige to assure the same safety level to everybody, prescriptions to protect human life are softer than in other non – historical buildings, while the building and its content aren’t perhaps so protected as necessary.

3.    the approach to fire safety in Italy
In order to take a look to the approach followed until now in fire protection in Italy, we must consider that other relevant regulations exist for specific activities, which we may find in historical buildings, that must be applied without any gap to those buildings.
As common rules to be applied actually in evaluating the fire resistance of elements, there are three different methods for determining the class of resistance: experimental methods, as specified in Ministry of the Interior circular n° 91 of 14th September 1961 (new reference: ministerial decree 16 February, 2007); simplified methods, by checking tables drafted by interpolating the data resulting from the experimental investigations in statistical series (UNI standard 9502/89, UNI standard 9503:89, UNI standard 9504/89); analytical methods, in accordance with the calculation methods indicated in the UNI standards referred to above and in the Eurocodes (1,2,3,5,6) (new reference: ministerial decree 16 February, 2007).
The experimental method asks that the duration of resistance to fire is determined on the basis of the results of a standardised fire test carried out by simulating heating with a fire chamber, applying a standardised temperature curve internationally accepted.
The brief list intends to show some of the rules that have to be compulsorily respected in planning the fire protection of  any building, explains that the framework in which a solution could eventually be found is extremely well defined, making rather difficult to individuate the different solutions that such special buildings need.

4.    the fire protection engineering approach
Fire protection engineering is addressed in the works of ISO Technical Committee 92.  Actually, the Technical Report 13387 (1999), which sets the most of the rules that have to be followed in an engineering approach to fire protection does not address the specific field of heritage, but states that, in the future, a specific branch of this discipline will study the characteristics of the analysis of fire protection in cultural and historical buildings.
In our context, where the problem is not designing brand new buildings but upgrading existing ones, the main interest of the engineering approach is bound to reach the equivalent safety level, which implies to select, alternative protective and preventive technical measures, based on the evaluation of the fire risk, in order to reach acceptable safety conditions for an activity.
Starting from this base, legislation shouldn’t indicate mandatory requirements about “what to do” but provide an information based both on the procedural and scientifically recognised methods of analysis and calculation, in order to offer alternative solutions. After a new approach has been brought in Italy with Legislative Decree n° 626/94 (now Legislative Decree n° 108/08), which incorporates the Community Directive for “improving the safety and health of workers at places of work” and with Ministry Decree dated 10.3.98, which implements it as far as concerns the risk of fire, this goal seems to be nearer, but with reference to historic or artistic value is still needed the specific knowledge that will let to enforce such approach in such a critical area.

5.    reasonable answers  to problems
When considering heritage, given that is impossible to apply prescriptive fire safety rule, performance-based approach has to be necessarily followed to solve the problem.  According to this approach, in the evaluation of the fire scenarios equal attention has to be given to life safety and heritage preservation. Moreover, the facts have demonstrated that the worst fires in historic buildings and towns have occurred in construction, renovation or restoration sites , that implies the need of a special attention to responsibilities of managers, in order to avoid unappropriate risk situations and to mantain always the level of fire safety that the risk analysis has shown as acceptable (fire drills, staff preparedness).
On the other hand, the very large number of rules that simultaneously has to be met (workplace heath and hygiene, accessibility), makes it difficult to imagine that a so wide range of prescriptions could be overtaken with a risk-assessment based process. Under this point of view, an appropriate package of precautions that meets the requirements the different regulation but which would allow performance design, is the only foreseeable solution. A check‑list, could be organised according to the following phases:

  • Identification and listing of the risks of fire in relation to the sources capable of sparking one off;
  • Forecasting of the danger of sparking off a fire in relation to the structures of the building.
  • Forecasting of the way in which the fire will develop.
  • Analysis and assessment of the means of escape.
  • Analytical valuation of the protective measures that can be adopted.
  • Definition of specifications for safety measures ‑ automatic detection systems and extinguishing systems on the basis of the ruling regulations.

Another point that is worth to be addressed is the use of simulations. There exist a certain list of experiences and records about their use in historic buildings. For historical buildings it must be stressed that simulations are due when their outputs could be used for assessing the actual safety of the means of egress. Therefore if their capacity is very large and their accessibility is sure, of course no simulation is advisable. On the other hand, simulations can be very valuable for assessing the actual need of interventions suggested by prescriptive standards. In other words, prescriptive standards often force to perform building interventions that have a hard impact of the original structure (e.g. divisions in compartments, safety staircases, etc.). Perhaps, in some conditions not all those interventions are absolutely needed: simulations can demonstrate it. Once more, if little or no intervention is required by prescriptive standards, simulations of the smoke flow patterns are unnecessary. Finally, simulations are affordable when boundary conditions are properly set. Under this point of view. First of all, one should verify is the boundary.

Given that the current situation shows that prescriptive rules can’t be used in protecting heritage, in the short period efforts must be done in order to acquire more profound knowledge of fire engineering approach. After having reached an adequate sensibility to the matter (both for public control officers and fire prevention designers), fire-risk analysis will probably make possible to select accepted procedures and sets of technical features (including a small group of mandatory rules necessary to assure the minimum safety and accessibility leve) that will meet both people and heritage safety and conservation issues.

Special aknowledgements has to be done to Mr A. Dusman of the Italian National Engineers Council, who is daily involved in the improvement of the culture of italian safety engineers.

L.Nassi, S.Marsella – La sicurezza antincendio per i beni culturali, UTET, Torino 2008