Portcullis House integrates a number of buildings of the Parliamentary estate at one centralised location, and has been conceived in the tradition of historic Thames-side palaces facing the river. Accommodation for 210 MPs is housed around a central courtyard in a six-storey rectangular block. The courtyard features shade trees and tranquil pools, and is surrounded by cafes and a library. It is covered by a frameless glass skin supported by an oak and stainless steel diagrid, and has become a meeting place and focus for Parliamentary life.
A gallery at the first floor provides access to a range of Select Committee Rooms. Above this are five floors of MP's offices that feature views over the courtyard roof, or to the surrounding historic neighbourhood and river embankment.
The building's structure is carefully coordinated with Westminster Underground Station below. The inner walls around the courtyard are supported by six massive columns, tied by a transfer structure of concrete arches. Gullwing precast concrete floor units span onto perimeter walls composed of sandstone piers. Welded box girders, doubling as air ducts, form spider-like roof frames on top of the piers. The chimneys are the terminals of a sophisticated, energy-efficient ventilation system.
The building received a BREEAM 'Excellent' rating, the highest available at the time of its completion.