What is the Sydney Opera House roof made of?
The Sydney Opera House roof is made of precast concrete shells covered with more than a million glazed ceramic tiles. The tiles were made in Sweden and have a special finish that helps keep them clean.
The roof's sail-like shells were the most difficult part of the building's design. Danish architect Jorn Utzon solved the problem by designing all the shells as sections of a single imaginary sphere, so they could be built from standard curved pieces.
The shells are made of concrete ribs that were cast on site and lifted into place with cranes. This approach was innovative in the 1960s.
Self-cleaning tiles
The roof is covered with 1,056,006 tiles, arranged in panels called lids. The tiles come in two finishes, glossy white and matte cream, creating subtle patterns.
The tiles were made by the Swedish company Hoganas. Their surface is designed to be washed by rain, so the roof rarely needs cleaning.
The Sydney Opera House was opened in 1973 and became a UNESCO World Heritage site in 2007. Its roof is often lit up during festivals such as Vivid Sydney.