The building is 14m high with a footprint of 100m x 35m. It is constructed against the side of the embankment where the Central Line runs. Its arrangement is determined by the position of the North London Line which runs through the station, dividing the new concourse in two.
The main station entrance faces Station Square with its bus station and taxi rank. From here, the building is entered at the east concourse where the ticket hall and retail space are located. Access to the North London Line is directly from this concourse.
An upper level walkway runs along the building's north western edge at approximately the same height as the embankment behind it. This level, readily visible on entering the station, is accessed by stairs, escalator or lift. This walkway bridges the North London Line, providing for interchange between its platforms as well as other services. The Central Line platforms and mainline rail services are reached through a new and existing pedestrian tunnel from the lower concourse, with connection by lifts and stairs.
The building envelope creates a strong external image. The roof springs from the concrete upper level walkway against the embankment, and sweeps upwards and forward in a curve, projecting over the 100m long glazed front elevation. The front and side elevations are fully glazed, as is the lower part of the curved roof to the north west.
The roof structure comprises a series of curved plate girder ribs. Each cantilevered girder is also propped by an 8m deep inclined truss that runs along the whole south side of the building, carrying the glass.