The 2,600 sq m Centre for Conservation will 'provide a world-class facility for all aspects of book conservation including education and training' and will house state-of-the art technical facilities for the national Sound Archive.
Once completed, the new building at St Pancras, London will bring together all of the library's conservation staff together for the very first time.
It will also allow the library to offer much-needed training opportunities for conservation professionals as well as offering visitors access to studios, demonstrations and lectures.
Designed with engineers Arup, the scheme includes a 40-seat seminar room, workshops, marshalling area and an extended terrace.
The museum's scholarships and collections director Clive Field said: 'This is an exciting project. It is the first new building at the Library's St Pancras headquarters since it opened, and it will also enable us to unite and enhance our conservation facilities for the first time.
'This will transform them into a world-class resource in which traditional craft skills will co-exist with scientifically-based research techniques,' he added.
The library plans to open the new centre in early 2007.