This building is an extension of the original School of Oriental and African Studies (SOAS) building, and is somewhat larger than its precursor, to which it is linked at all floors. Having a square footprint It was built at the same time as the nearby Institute of Education (also by Lasdun). Constructed chiefly from concrete (both precast and in-situ) the lower two floors form a plinth which houses the building's 150 seat lecture theatre and other large spaces. Above this are offices, seminar rooms and the main library, the base of which is off-set to the north east corner, with the floors on the south and west sides terracing down to it. A large diagonal grid roof crowns the space. Lasdun created four external terraces on the roof of the plinth that were always underused. In 2006, as part of a rolling programme of refurbishment and improvement, John McAslan and Partners enclosed the two larger terraces, on the north and east sides, to create two new double height reading spaces.