While the catastrophic fire at the Notre-Dame cathedral unfolded, the role played by renovators on site was quickly put under the spotlight.
Investigators looking into the cause of the fire have now quizzed contractors carrying out renovation work on the 12th century building’s roof and spire at the time of the blaze. And while no official cause has been given, the renovation work has been identified as the “likely” origin of the fire.
And sadly, Notre-Dame is just the latest casualty in a long list of famous structures severely damaged by fire during renovation works.
The Cutty Sark fire in 2007 started because an industrial vacuum cleaner was left on for two days during its recent £25M renovation project. The Windsor Castle fire in 1992 started when a restorer’s lamp set fire to curtains, damaging 100 rooms including the castle’s main banqueting room. More recently the fire which ripped through the Mackintosh Building in Glasgow last year was again started during a renovation programme.
So it begs the questions: What should owners of historic buildings do to prevent a fire during restoration works? And, what are the challenges of working on historic buildings after a fire?
Historic England senior structural engineer Toby Murphy said that before restoration work takes place on a historic site, the organisation encourages building owners to work with their local fire brigade to make an emergency plan to cover to possibility of a fire breaking out.
As well as including an evacuation procedure, the plan should prioritise areas of a building to be saved first, it should identify the location of artefacts which need protecting are and set out what the renovation is likely to include.
“With historic buildings, if it’s at the stage where they [firefighters] believe entering the building is too dangerous, the damage is quite sustained and they’re not sure much can be saved, there will be a difference between a listed and an unlisted building,” he said. “The fire brigade will put in a bit more effort for a listed building because it is assumed that trying to save some of it is more important, rather than with a more modern building it could be rebuilt again, and that’s acceptable.”
In the unfortunate case that a fire does break out, Murphy said that the immediate concern is the stability of the building; walls which were previously stabilised by damaged floors and internal walls may need temporarily propping. Materials such as timber may appear to be irreparable, but under a layer of charring, “clean” wood still capable of carrying loads may be in tact.
Depending on the ferocity of the fire, stone is unlikely to be affected, however if limestone is exposed to temperatures of more than 800°C it can transform into a “lime putty” with the addition of water (from the fire service’s efforts to put out the fire).
Cast iron can perform well in the actual fire he said, but is more a problem when cooled rapidly by water from fire hoses. This often results in thermal shock and causing the material to shatter.
The next concern is water.
The water can come from rain rain or water from firefighters tackling the blaze. Either way Murphy said that the building must be allowed to dry out.
“Be it plasterwork or timber structures, if it’s not protected, within six months you’ll start to see obvious damage and if it’s left for longer that could turn to permanent damage,” he said.
Whether or not the building is restored is a matter of context he said. Should the building reflect its history, as in the example of Second World War bomb damage to St. Paul’s Cathedral which remains on show, or is it more important to recreate what was there before?
In planning work to avoid fires, Historic England’s recommendations are more onerous than those for a normal building.
Its first recommendation is that any hot works on site are avoided. Elements which require welding should be removed if possible, with the work carried out in a safe, controlled environment.
Should hot work such as welding need to take place, it should not be carried out on a Friday or after midday to reduc the possibility of a fire occurring when the site is unoccupied.
“It is well known that refurbishment work presents a fire risk factor. This is because of hot work [welding, for example] and sparks that can be generated by certain processes such as grinding and sawing,” Tarada said.
This was the case when a fire erupted in the 115-year old Mandarin Oriental hotel in London last year. While undergoing restoration works, a spark from an arc weld landed on the felt lining of a planting façade which then spread the fire over a number of floors.
With a massive renovation of the Palace of Westminster set to take place over the next few years, the contractors involved will no doubt be on high alert to avoid the devastating consequences of yet another cherished building succumbing to fire.
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