International architects have been invited to submit designs for a £59 million (SEK 795 million) extension to Asplund's 1928 masterpiece, including new lecture halls, studios, a café and a restaurant, that will effectively quadruple the public space.
A separate £3 million (SEK 40 million) restoration of the original library is also planned.
According to the SAA design brief, the library was 'too small right from the beginning'. It says the library now requires 24,000m 2of floor space, compared to the current 14,000m 2- made up of the existing Asplund building and a collection of more recent annexes.
The Public Library is the collective term for Asplund's structure, housing the main collection, and its over-spill annexes, containing the international titles, periodicals and the Swedish Institute of Children's Books.
Crucially, Asplund's library, its landscaped park and pond facing on to the Sveavagen road and the Observtorielunden - a grove around Observatory Hill - will remain intact.
The proposed development is earmarked for the three adjacent annex buildings along the Odengaten road and the northern slope of Observatory Hill. According to the SAA, 'It is here that the extension with a possible connection to the Asplund main library shall be proposed'.
According to Stockholm's Mayor, Annika Billström, it would be 'disastrous' to attempt to adapt Asplund's original design to meet predicted demand on the library's resources.
'In order to be able to maintain and develop the public library as the main library of the city and as a central public meeting place for learning and reading, new activities and functions must be added in a new extension to the Asplund building,' she said.
Asplund originally planned the library in tandem with Erik Lallerstedt's concept for a new university campus on the hill. The university moved out of the district in the 1970s but the character of Observatorielunden as Stockholm's academic quarter has remained.
The proposed extension will complete the original vision of Asplund and Lallerstedt, says the SAA, while the library restoration will correct areas of 'careless' maintenance.
The SAA design brief explained: 'Original windows and glass sections with their elegant thin metal framing and single glazing have been replaced over the years with varying results and at times downright carelessly.'
The closing date for phase one of the two-stage design competition is 27 October 2006. A shortlist of five entrants will be announced in May 2007.
For more information, visit www.arkitekt.se/asplund.