Main Library was part of the Great Court buildings designed by Hennessy and Hennessy in 1935-1936. It consisted of two floors with a glass ceiling in the light well in the centre. Main Building was designed to be extended with an additional three floors, with high ceilings and a large light well in the centre. When the Library had insufficient space for students and books it was decided to go ahead with the extension of three more floors, as specified by Hennessy and Hennessy. Birrell proposed five additional floors instead of the three, the installation of passenger lifts, fluorescent lighting, and air-conditioning. Birrell was responsible for the internal arrangement and finishes. This file comprises 15 plans for alterations and additions to Main Library. Includes: sketch of lower ground floor (now Level 1), working drawings for 1st to 5th floors (now Level 3 to Level 7), stair details and compactus shelving.

Main Library was later known as Undergraduate Library; with the construction of Central Library in 1971 its name was changed to Duhig Building; and later, around 2000, to Duhig Tower.

Prior to the construction of the J.D. Story Administration Building, University administration facilities had been housed within Main Building (now know as the Forgan Smith Building). Main Building had undergone many alterations in response to the changing needs of the university administration. In 1959 the Senate decided a new Administration Building should be built. Other building priorities delayed designs being drawn up. In 1962 plans were submitted to the Australian Universities Commission (A.U.C.). Changes requested by the A.U.C. delayed construction which was to be a two stage process: Stage One was completed in October 1965 and Stage Two in October 1966. Plans include: site plans, window details, detail of senate table, floor plans, electrical services plans, roof plans.

There are 6 volumes (sets/presentation volume/office copy sets) with plans as well as individual plans; the total number of plans for this building in this subseries are 281. Not all have been created by James Birrell.