While modern brick houses were being built in London’s suburbs, the City of London in 1666 consisted mainly of old timber framed buildings. Their upper floors were often built projecting out over the streets. The crowded nature of these houses meant that fire could easily spread between them and the narrowness of the streets often prevented fire-fighters and their equipment from getting to fires.
People in London used fires to cook food and heat houses, and candles for lighting. There were many London industries that depended on fires, such soap boiling, baking, dyeing, brewing and metalworking. According to John Evelyn’s "Fumifugium", London’s air was full of smoke – people’s clothes and houses, and even the rain turned black from soot. He argued these trades should move outside London to keep the air clean. This would also have lessened the risk of serious fires.