Seikado Library (1933)
[Sloped roof extension]

Seikado Bunko was a private library built by Iwasaki Koyata in 1924, and surviving blueprints show that it has been expanded several times. Here, we would like to focus on the expansion of the stacks, which took place in 1933. Although it was an expansion, it was not to add more rooms, but to change the flat roof into a sloped one. The three-story flat roof was partially removed and reinforced with reinforced concrete beams, and a new sloped roof with a gentle curve was constructed. This roof is still in place today.

Not only is it impressive how the intricate designs of the gutters and eaves were realized all with a concrete framework, but the building also features ingenious structural design, such as the efficient use of main bars by bending them. It is also interesting to note that the size of the rebar, which had previously been measured in inches ("), began to be measured in millimeters (mm) around this time. Perhaps this was the time when the standards for rebar changed.

However, what is most puzzling is why a sloped roof was added. The first thing that comes to mind is that it was due to rainwater leaking, but the structure before the addition had a proper water slope, and there were no visible areas such as skylights that could be the cause of rainwater leaking.

A more realistic explanation is that the sloped roof was added in the Imperial Crown Style, encouraged by the era's desire to promote national prestige. The Imperial Crown Style was selected in a competition held by the Tokyo National Museum two years prior to this drawing (1931), so this timing makes sense. Furthermore, considering that Seikado was primarily intended to house ancient Chinese art, it makes sense that the roof was designed with a Chinese-style curve.