This paper describes the design and construction of the two terminal buildings in phase 1 of the £4·3 billion Terminal 5 development at London's Heathrow airport. A total of 40 000 t of steel was used to create 280 000 m2 of space in the dramatic main terminal building, T5A, including forming a clear span roof of 156 m by 396 m to enclose it. In addition to high visibility for passengers, the design provides maximum flexibility for future modifications. In the first of two satellite buildings, T5B, 600 000 m2 of posttensioned flat slabs were cast using minimal amounts of formwork and site labour. Building these vast structures at the world's busiest international airport also meant all construction operations had to be undertaken within a highly restricted space and with no cranes allowed above roof level.

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