The Red Book

Within six months of the announcement of his winning design, architect Jørn Utzon was required to produce new plans, which would become the Red Book, presented in March 1958.

The Red Book, which Utzon dedicated to New South Wales Premier Joe Cahill, was not just a beautiful document.

Alongside an undeniable quality of design and aesthetics, the reports from Utzon's consultants and the overall effect of conveying a buildable structure, the Opera House moved far closer to becoming a real building.

When engineers Arup and Partners requested that Utzon define the curves of the roof, he took a plastic ruler and, holding it perpendicular to a table, made it bend, tracing the curves. He sent them to London, explaining these were the shapes he wanted.

The outcome of the first exchanges between architect and engineer produced an initial sketch of the roof in which every curvature is different – a structurally unsound form with difficult bending moments near its footings.

However, this first geometrical approach to the shells was also visually very beautiful in a distinctly different way to the drawings Utzon had submitted for the competition.

The ridge profiles were much higher and pointed now, and the end shell form of Utzon’s competition drawings no longer cantilevered, like a cliff cave over the sea.