It was under Napoleon III that the great works of transformation of Paris were initiated. Baron Haussmann regulates everything, the height of buildings, roof coverings and the size of wide avenues in Paris. Zinc roofing (lighter to transport and install than slate) and small chimneys became the rule in the city in the middle of the 19th century. Their stock, more or less high, is made of refractory brick and the pot is made of clay. The roofs of Paris have been listed as a UNESCO World Heritage Site since 2014.