The Leathermarket Business Centre complex was formerly the London Leather / Hide and Wool Exchange built in 1878, the Exchange and the surrounding warehouse buildings are grade two listed. Since the 1990s conversion it has thrived as a business centre offering facilities to an arts-based clientele including theatre groups, jewellery makers and glass blowers. Due to its popularity, the potential of the site was maximised by adding an extra floor onto Lafone House and Trowbray House. The extensions were designed as a steel and glass structure with a shallow pitched lead coated stainless steel roof, clearly a modern addition but in sympathy with its surroundings. A new form of “heavy lightweight roof” was developed, with self finished concrete planks laid on the slope, supported by a lightweight exposed steel frame. The high thermal mass roof, with directly exposed concrete surface provides the main means of temperature regulation and natural ventilation is achieved by the ridge ventilators and perimeter opening windows using the stack effect.