Allies and Morrison's No 1 Piccadilly Gardens is the focal point of the city centre's public square regeneration
An office block designed by Allies and Morrison is the latest addition to the regeneration of Manchester city centre – a regeneration in which commercial buildings are playing a particularly civic role.

No 1 Piccadilly Gardens is a freestanding, seven-storey slab of offices set above a ground floor of shops and restaurants, but its significance lies in the fact that it rises up at one end of central Manchester's largest public open space, Piccadilly Gardens.

Although the block has been built on part of the public gardens, the £5.5m paid by property developer Argent to the council for the site was used to improve and extend the gardens into streets, which have now been closed to traffic.

The 15,300 m2 slab is the final chapter in the transformation of the square from a dowdy fairground to a stylish civic plaza worthy of Barcelona or Paris. It stands both as a gateway to the city centre on the approach road from Piccadilly Station and as a backdrop to the public gardens. The redeveloped gardens, designed by EDAW, were completed two years ago and boast a sculptural concrete pavilion by Japanese star architect Tadao Ando.

The rectilinear slab block has an urban presence that is suits its city-centre setting. It is spare, modern and functional, yet has finely proportioned, classical undertones. The elegance in the regular rhythm of 7.5 m bays combines effectively with the crisp, robust detailing of the red brick facing and deep window reveals.

On the first two floors, the external window walls are set back from the structural frame to create covered pedestrian colonnades on both sides. Similarly, on the top two floors the facades break into grand loggias on either side with square, double-height bays and window walls set back behind continuous terraces.

The insistent, rectilinear geometry of the facades is interrupted by a diagonal recess that leads to the entrance hall. It follows on as a double-height mall, running diagonally through the slab, and is repeated upwards through all floors.

The block was built for £23m by Carillion Building, with Weedon Partnership as executive architect, Arup as structural and services engineer and Faithful & Gould as quantity surveyor.