The National Diet Library (NDL) holds approximately 36 million library materials, the largest collection in Japan. It increases by about 200,000 books and 600,000 magazines and newspapers a year. The NDL also holds materials of various forms and contents such as maps, music CDs, doctoral dissertations, etc. These materials are preserved with great care to be used for wide-ranging services provided by the NDL as the parliament’s library as well as the sole national library in Japan.

Unlike ordinary public libraries, most of the collections are stored in the stacks, and they are delivered to counters by the staff in response to users’ requests. Readers are not allowed to enter the stacks. The NDL chose the closed stack system to achieve a good balance between the preservation and utilization of the large collection.

Showing the inside of the stacks that are normally closed to users, this article introduces the structure and facilities of the stacks, and many different efforts made for the preservation and utilization of the collections.

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The first phase of construction of the Main Building was finished in 1961 and the construction was fully completed in 1968. The stack unit is 45m by 45m and is located at the center, surrounded by office units (Figure 2 below).

At the planning phase, four alternative layouts were considered for the stacks: (1) stacks at the center of the building, (2) stacks at the bottom of the building, (3) stacks around the outside of the building and (4) stacks at the rear of the building. The stacks-at-the-center system was adopted after discussions among the library staff and at a committee composed of specialists. In the discussions, it was pointed out that the Library of Congress (U.S.), which had functions similar to the NDL, used the centralized stack system, and all offices would benefit from being situated close to the stacks.

<Tiered stacks>
Each concrete floor of the stacks is divided into three (partly two) steel-frame decks, and in total the stacks comprise seventeen decks (Photo 2). Square steel pipes for supporting steel-frame decks are arranged in every 1.4m x 0.9m area, and also serve as poles of bookshelves. The poles have holes every 30mm and shelf boards can be set at any level.

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The construction of the Annex was completed in 1986. All the stack spaces, consisting of eight floors, are placed at the bottom of the building and the foundation reaches to a depth of 30 meters (Figure 1 below). As the Tokyo Main Library is situated next to the Diet building, the library building needed to be at as a low level as possible to preserve the landscape. Another reason for the depth is that there is firm ground, called the Tokyo gravel layer, around 30 meters below the surface, which is suitable for building the foundations.

Stacks below ground are less affected by the outdoor air temperature throughout the year and so are cost-effective and energy-saving. There is less shaking from earthquakes in the underground stacks, which is also an appropriate environment for preservation. To avoid flood damage, a great threat for library materials, the outside of the outer wall and the flooring of the ground floor are waterproofed, and thus prevent the inflow of rainwater and groundwater.

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* Click the figure for a larger image

*Figure 1. Sectional plan of the Tokyo Main Library

*Figure 2. Floor plan of the Tokyo Main Library

Book conveyer systems
Book conveyer systems are installed to deliver materials effectively. On each floor of the stacks, there is a station where the conveyer system is controlled (Photo 3), and materials on trays come and go between the stacks and counters (Photo 4). As ID numbers are assigned to each tray, we can identify the tray’s position at any moment by using a tracker.

Photo 3: Book conveyer system control station

Photo 4: Trays on the conveyer

Light well
A light well is built into the stacks of the Annex so that the sunlight reaches right down to the eighth basement level (Photo 1). It eases the worker’s feeling of oppression in the closed environment of the underground stacks, and at the same time, serves as an insurance against a power outage.

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