A work of art in itself, the Sydney Opera House construction was also a technological leap forward and the begetter of later work by Gehry, Hadid et al.
The Riddle of the Shells
Once the podiums of the Opera House were defined, the overwhelming problem of the shape of the roof arose.
Utzon’s initial sketches showed these as relatively squat, free form concrete sail shapes which were to be covered with white tiles. But the shapes didn’t work. They simply couldn’t be built to bear the loads or provide the performance spaces required.
Utzon and Ove Arup, his engineer partner, solved the problem of the sails by changing them to shells – from a series of parabolas to parts of a sphere. But the builders were still left with the problem of how to build them, and how to attach the tiles.
Tests showed that the traditional system of attaching the tiles on the completed concrete shells wouldn’t work. The tiles would fall off in no time because the differing thermal properties of the tiles, the concrete and the adhesive meant they all expanded and contracted differently with changing temperatures and conditions. It also wasn’t going to be practical to place over a million tiles by hand.
Sydney Opera House Construction Technology
The history of the Sydney Opera House Australia is a history of technological breakthroughs and re-thinking of traditional work practices. Utzon utilised what he called ‘additive architecture’. He used pre-fabricated components – often made on site – with an incremental, organic assembly of the whole. He designed processes to enable builders’ labourers to achieve what previously could be done only by master craftsmen.
He built 26 chevron shaped ’tile beds’ under the monumental steps. These were essentially beds made to the exact measurements of various ribs the finished shells.
The tiles were laid face down in these beds, in the right pattern of cream and white.
Grooves were provided (for drainage) and the joints partially filled with heated animal glue to prevent grout getting into the surface of the tiles.
Their backs were then covered with galvanised steel mesh and mortar. They were steam cured for several hours. Finally, they were cleaned and stored.
Special moulds were made to cater for warped surface requirements on the side shells. This work was all done during the night by relatively unskilled workers.
The tile lids made overnight were stored on a “butchers’ rack” arrangement to prevent their distortion.
During the day they were swung up into place by the tower cranes and assembled in the air.
Each tile lid was screwed on to the appropriate concrete rib using a spigot and socket system. This provided a vacuum between the tiles and the concrete structure, thereby overcoming the problem of attaching tiles onto concrete.
The problem of differential stresses from one tile lid to another was solved by making each tile lid independent of adjacent lids.
This was achieved through adjustment of the spigots and sockets. Each tile lid can thus expand and contract in any direction without warping or damaging tiles.
It was a very economical system, accurate and fast. The famed cost overruns of the Opera House in Sydney certainly didn’t happen during this process. Michael Lewis, senior partner with Ove Arup & Partners, project engineers for the construction of the Sydney Opera House, set the total direct cost (including materials) of construction of the Sydney Opera House pre-cast tile lids at AUD$3.95 per square foot.
The Sydney Tile
The tiles used in the Sydney Opera House construction are 120mm square. Even today they are known as the ‘Sydney tile’. What’s more, you can buy them to use at home!
They are made from clay and, before they’re fired, they’re covered with a fine mesh and brushed over with more of the clay, this time containing a small amount of crushed stone. This gives them a granular texture and it stops excessive glare in the harsh Australian sunlight.
From a distance the tiles all look white, but they are really a combination of two colours: cream and white, and two types of finish: matt and glazed.
They are laid as diamonds. The cream, matt tiles are at the edges of each strip (known as a tile lid) and the white glazed tiles are in the middle. Eight different tile sizes are used on the shells.
Ceramic Tile Pattern
As well as the vertical pattern made by the colours and the grouting, Sydney Opera House architecture has a horizontal pattern made by the chevron, or inverted V shape, in which the tiles are laid across the shell.
It took Joern Utzon, three years of work with Swedish tile manufacturers, Höganäs, to produce the effect he wanted. He’d seen mosques in the desert which glistened in spite of sand and dust storms, and wanted the tiles of the Australia Sydney Opera House shells to have a similar quality.
They absolutely do, constantly reflecting Sydney harbour and its changing skies.
One of today’s great Australian landmarks, and a mainstay of Sydney tourism, the Sydney Opera House construction was also the story of turning a vision into reality against all the odds.