Almost 1,100 practices from around the globe entered the two-stage contest, which was launched by the Swedish Association of Architects last June ('Iconic' Stockholm library launches competition for massive extension).
These proposals, which will effectively quadruple the library's public space, will be delivered in tandem with a £3 million restoration of the original building.
It is understood that as part of the second phase of the competition, the architect team will be given a 'new brief' by the City of Stockholm.
The winning design is expected to be announced by the end of the year.
Speaking about the 'incredibly difficult' judging process, a spokesman for the jury said: 'The solutions offered demonstrated a very broad spectrum of ideas, many of which were of a very high quality. The proposals have provided insights and provoked thoughts as to how this very difficult and challenging task can be achieved.'
It is hoped the new library building will be open by 2013.