University of Helsinki

Churches on fire

Many medieval Finnish stone churches have gone through hard times over the centuries. Throughout the ages, fire has been one of the biggest hazards.

In the Middle Ages, work started on 104 stone churches in Finland, with the most active construction work taking place in the 15th century. Most of these churches are in the fertile coastal regions of the Gulf of Finland and the Gulf of Bothnia, which is where habitation at the time was concentrated. Research by Markus Hiekkanen, Adjunct Professor of Medieval Art History, notes that at least 32 of the Finnish stone churches have experienced fire at some stage of their history, with some damaged by fire on more than one occasion.

“Turku Cathedral has suffered the most incidents: there have been nine recorded fires there. During the past 21 years, three medieval Finnish stone churches have been targets for arsonists. The most recent case was a year ago, when Porvoo Cathedral was burned down, an event which was widely covered in the media,” Hiekkanen says.

Hiekkanen has studied the different stages that the Finnish churches were built in, and his research is well known in the provinces, too, since he showed in his thesis from 1994 that many of Finland’s medieval churches are not as old as they were believed to be. In looking for timber samples for dendrochronological dating, he discovered signs of fires at several of the churches, even if there was no supporting documentation.

“Then again, I also discovered that the churches, for example, in Lempäälä and Keminmaa had not, in fact, burned, even if some sources claimed that they had. A researcher has to go crawling around in the church attics and lofts, where there are clear signs to be seen that can provide added information, or in some cases overturn the claims of other sources,” Hiekkanen says.

A bolt from a clear sky

The reasons underlying the fires that have de-stroyed stone churches are generally lightning strikes, careless handling of open fire, or arson, something that was historically connected with a state of war. Nevertheless, the solid traditional building technique used in these churches has preserved them from the worst ravages of fire. The churches were built of natural blocks of stone dug out of the fields in the local parish, and every farm was duty bound to bring such blocks to the building site. The blocks of stone were then split and lime mortar was used to build walls that were about two metres thick. Brick was used for door and window openings and on the end gables. The roof structures were generally pine, and that was also sometimes the case with the floor.

The way fire behaves in a church building depends on where it starts. Before the end of the 18th century, when lightning rods were introduced, the main cause of fire was generally lightning.

“Almost without exception, lightning struck the ridge of the roof and fire then spread downward from the roof into the roof structures. Such a fire generally became very strong and only stopped when it had consumed all organic matter. The timber structures in the attic consisted of extremely dry pine with a high resin content, and since the gables had light shafts and other apertures, the fire was also supplied with oxygen. What’s more, the churches had tarred shingle roofs, which also burnt like torches,” Hiekkanen says.

The sheer force of the fires is sometimes visible on the interior surfaces of the gables, and traces are also easy to spot in the form of charred timber in the scaffolding holes. The surface of the rocks used as building material is regularly splintered by the force of the fire, but this has in no way undermined the durability of these big stones. Despite a fire, a brick wall may still look as if it had been built yesterday.

Brick vaults afforded protection

Brick vaults acted as effective firewalls, and helped preserve the church interiors without major damage. According to Hiekkanen, these vaults might even be a deliberate method used by the old master stonemasons to protect the most valuable parts of the building against the damage wreaked by lightning strikes. The protection also worked in situations where a fire started because adjacent buildings burned and sparks flew onto the church roof.

“The structures of the roof trusses and beams could be replaced at a much lower cost compared with interior objects such as ceremonial chairs and altarpieces, which were major investments. If it were not for the brick vaults, the wonderful medieval interiors of the churches at Sauvo, Hollola and elsewhere would not have been preserved. The roof trusses and beams usually came to about one tenth of the value of the interior of the church, at a rough estimate,” Hiekkanen calculates.

Hiekkanen has not found a single mention of a fire that would have started from a candle or other source of light in the church. This is surprising in view of how much open fire was used in churches in the form of candles. For instance, it was traditional that every house, or even every parishioner, arrived at the service on Christmas morning with a candle.

“Add to this the fact that we know that it was traditional to cover the church floor in straw at Christmas; you would think that would be a fateful combination,” Hiekkanen says. “According to the sources we have so far, there were no fires that started in the inside of stone churches until the late 19th century, when cast-iron heating stoves were installed.”

Increased incidence of arson

From the 20th century onwards, the main reason for church fires has been arson, when you include all fires at churches in Finland. During the past 100 years, 80 Finnish churches of different ages have been deliberately set alight, most of them in the past decades. Fires have quite often been started on the spur of the moment.

In 1997, a burglar who was covering up the signs of a burglary set the 500-year-old church of Tyrvää on fire from the inside. The entire wood interior, the timber vaulting and the roof were destroyed. Although the interior of the church was completely lost, certain items of furniture and other wooden objects that had been kept in the sacristy were preserved undamaged. Even the brochures about the church, which were kept there, were preserved, though in a very sooty condition, because the room had a brick vault for a ceiling and did not contain enough oxygen to sustain a fire.

“In my opinion, the damage to the Tyrvää church could have been considerably less if the nave of the church had been given a brick vault ceiling in 1506–1516 when it was built,” Hiekkanen says.

On the night of 29 May last year, a young man set the medieval church in Porvoo on fire. He was drunk at the time, and on the spur of the moment he set fire to the church from the outside, where fire spread rapidly in the roof structures. The news footage showed the danger of the situation: the flames shot up into the sky and the surrounding timber houses were also in danger that night, as the wind carried sparks from the fire hundreds of metres away. The belfry nearby also caught fire, but the rescue services were able to extinguish the fires at an early stage.

Hiekkanen visited the site immediately after the fire to examine the extent of the damage. This time, there had been a stroke of good luck.

“There was just slight smoke and water damage to the interior, very limited damage really compared with what could have happened. The Porvoo church, which dates back to the 1450s, is a unique building in many ways, and it features very prominently in Finnish history. The interior of the church contains a number of details of irreplaceable value. The wonderful Rococo interior is the only complete whole on this scale in a Finnish stone church. The impressive double gallery is also of a kind you no longer find in the other stone churches.”

The fact that the fire could be put out in time proves how effective brick vaults are as firewalls. The worst that happened was that the roof and its support structures were destroyed.

“Today’s fire-fighting techniques can unfortunately complicate the damage caused. There are huge volumes of water involved, pumped with great force, and the reach of the water jets is also great. Water sprayed onto burning hot walls tends to damage the external surface of the walls. One of the future challenges is to study how to prevent additional damage in connection with extinguishing fires. Fortunately, there is already discussion on this topic,” Hiekkanen says.

Arja-leena Paavolainen

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