Glazed tiles (Chinese: 琉璃瓦) were used in China since the Zhou Dynasty as building material for roof top. During the Song Dynasty, the manufacture of glazed tiles was standardized in Li Jie's Architecture Standard. In the Ming Dynasty and Qing Dynasty, glazed tiles became ever more popular for top tier buildings, including palace halls in the Forbidden City, and ceremonial temples (for example the Heavenly Temple).
There are two main types of Chinese glazed tiles: glazed tubular tile and glazed plate tile. Glazed tubular tiles are moulded into tube shape on a wooden mould, then cut in two halves along their length into two tubular tiles, each semicircular in shape. A tube shape clay mould can be cut into four equal parts, with a cross section of a quarter of a circle, then glazed into a four plate tire.
Glazed plate tiles are laid side by side across and overlapping on each other. In the Song Dynasty, the standard for overlap was 40% overlap, and was increased to 70% overlap in the Qing dynasty. With the Song style 40% overlap, it was not possible to have triple tile overlap, there was a 20% gap between the first plate tile and the third plate tile. Hence, if a crack developed in the second tile, water leak was inevitable. On the other hand, with the Qing dynasty style 70% overlapping, the first plate tile was overlapped 70%, 40% and 10% by the second, third and fourth tile respectively; thus even if the second and/or the third tile developed cracks, there would be no rain leakage.
Glazed tubular tiles used at the eave edge are called eaves edge tubular tiles. They have an outer end made into a round shape top, often moulded with the pattern of dragon. Eave edge plate tiles have their outer edge decorated with a triangular shape end to facilitate rain fall.
- Song dynasty Li Ji Yingzao Fashi, chapter 15, Glazed tiles