The Great Fire of London: a step change for concrete and masonry

3 Aug 2016

This autumn sees the three hundred and fiftieth anniversary of the Great Fire of London, which started in a bakery on Pudding Lane on 2nd September 1666. The conflagration was finally put out on 5th September, after 70,000 of the 80,000 inhabitants of the City of London had been made homeless. There were few reported casualties, but many historians feel that there were many more than the six confirmed deaths as the poor were not counted and the heat was such that the fire melted pottery and so there would not have been any remains of the victims.

The spread of the fire was exacerbated by the strong east wind which blew the flames over the firebreaks which were the main way of controlling the fire spread. Another factor was the closeness of the buildings, particularly the way that upper storeys were cantilevered over the road so that there was little space between one side of the street and the other. 

Most of the buildings were made of timber, despite it being acknowledged at the time that timber built houses were more prone to fire than masonry built houses. While we all remember the Great Fire of 1666, there had been many other significant fires in London before that, notably in 1135 and 1212 and thatched roofed houses had been banned in London after the 1212 fire. Masonry houses were, at the time, more expensive to build than timber houses, so the houses of the poor were normally timber.

After the 1666 fire the London Building Act of 1667 banned the use of timber framed houses in the City of London and stated that masonry be used as the structural material. This was extended to Westminster in 1707, and to the rest of London by 1774. There has been no great fire in London since the 1666 fire, due in significant part to the restrictions laid down in the London Building Act of 1667 and subsequent Acts.

The present day

Fire is still a hazard to buildings and most fires even today happen in domestic settings. Using masonry or concrete frames is still a logical solution to the hazard that fire presents as concrete and masonry are non-flammable and thus do not add to the fire load within the building. Studies in Sweden have shown that where houses are built in heavyweight materials such as concrete and masonry the cost of repair after a major fire is, on average, a fifth of the cost of an equivalent timber framed house.

In the UK, the Building Regulations govern the design and construction of buildings, including residential buildings. Each of the four constituent parts of the UK has their own regulations, but all cover fire as one of the hazards to be designed against, forming: Part B of the Building Regulations in England, Section 2 in Scotland, Part B in Wales and Part E in Northern Ireland.

The regulations mostly cover life safety of the occupants of the building and firefighters. Reducing the damage caused to the building is not covered by the Building Regulations. However, for many buildings it is important that the building can be repaired quickly, whether it is a house or a school or an office. Finding somewhere else for the occupants to use while the fire damaged building is repaired can be difficult and causes great upheaval.  It has been calculated that over half of businesses affected by fire cease to trade within the twelve months after a major fire. This puts livelihoods at stake, even if lives are not lost. With their fire-resisting properties, concrete or masonry can provide more than just life-safety protection, but can also provide reduction to the damage done to the building.  As for spread of fire between buildings, it can be argued that current building regulations are predicated on centuries of building in non-combustible masonry, but the regulations in themselves no longer require this. Hence with current regulations there is a potential backward step with an increased risk of spread of fire to adjacent buildings, which proved such a problem in the Great Fire of London.