Structural Designer

Structured Environment

Client Name



Saitama Prefecture, Japan

Images: © Koichi Torimura / Structured Environment / Alan Burden


The steel and glass structure of this small private Japanese house involves intricate diagonal intermeshing of the floors, and the integral zigzag stair system provides the principal earthquake resistance in the building. The columns at the four corners are only 44.6mm diameter steel bars, carrying only vertical loads, and are stabilised against lateral buckling by the horizontal moment frame action of the box beams that form belts around each half-storey level. The skin of the house is pure steel structure and glass for maximum transparency, and even with the central stairs acting as the seismic core the system achieves incredible lightness and transparency.

Judge's comment:

This unusual building demonstrates what can be done by re-thinking conventional structural solutions for domestic buildings, resulting in an innovative and eye-catching composition. With the significant seismic resistance being provided by the stair core, and the very slender corner supports restrained by an ingenious connection detail, the engineer has created a light and transparent façade to reveal the whole assembly as an integrated structural system.

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