The Willis Building

The Willis Building is an office building designed between 1970 and 1971 by Foster Associates, with structural engineer Anthony Hunt, and constructed between 1973 and 1975.

The building's construction utilises a reinforced concrete frame clad in bronzed glass, with a flat roof covered in turf and edged by a hedge slightly set back from the perimeter, allowing access for a maintenance crane. The plan is irregular, incorporating a curved external wall that follows the site’s boundary.

The structure is four storeys high, topped by a recessed, steel-framed, glazed pavilion on the fourth storey, set back and leading to a grassed roof garden. Columns are spaced at 14-metre centres, with closer columns at 7 metres along the perimeter, supporting cantilevered flat plate and waffle concrete floors. The building is fully glazed with specially commissioned toughened, bronze-tinted glass from Pilkington, which is suspended from the perimeter cantilever above the second floor. The glazing panels, 2 metres wide, are free of mullions and secured by rectangular patch fittings at the junctions and intermediate floor levels. An entrance to the loading bay is accessible from Princess Street. Pedestrian access is via revolving doors of bronzed glass within simple black frames, located on Friars Street.

The interior was designed as a unified whole by the architects. A central 'atrium' accommodates three paired escalators, lit by a tubular metal-framed roof. These escalators effectively divide the flexible, open-plan office space on the first and second floors into two zones. Fixed service facilities on the ground and third floors include a former swimming pool, computer and plant rooms on the ground floor, and a restaurant, conferencing, and presentation suite on the third floor. Four service cores house the stairs and toilet facilities on each level; the lifts are in a separate housing.

The architects designed an integrated service system, including raised floors with access panels for power and communications cabling, and suspended ceilings with polished aluminium channels for air-conditioning, ventilation, smoke detectors, and glare-free lighting with parabolic reflectors. The waffle slab ceiling on the ground floor is painted white. The colour scheme, floor coverings, finishes, and furniture were carefully selected by Foster Associates. The ground floor features green studded rubber flooring, while the upper floors have green carpet. Modular steel partitions surrounding service areas are painted yellow.