Preserving a 250-year-old Tokyo residence with modern seismic technology

Mitsui Fudosan and Mitsui Home have completed a seismic retrofitting project on a historic 250-year-old residence in Setagaya, Tokyo, blending modern engineering with traditional architecture to preserve the building for future generations. The project on the former village headman’s house from the Edo period was finished on 31 July 2025.

Many traditional Japanese wooden houses, known as kominka, possess immense cultural value but lack the structural resilience to withstand major earthquakes. This poses a risk for Japan’s architectural heritage. This project was began as a response to the owner’s wish to preserve the historic house for the next generation in a safe condition, while keeping it as intact as possible.

Mitsui Home, which handled the design and construction, implemented a two-part strategy that enhanced safety without sacrificing the building’s character. First, the company installed the “Hi-Dynamic Seismic Control Method”, a system developed by Edogawa Wood Industry. This technology uses multiple oil dampers within the walls to absorb seismic energy, reducing stress on the building’s frame. Its design is suitable for traditional structures and minimises the need for demolition, allowing key features such as the original floors, ceilings and veranda to be preserved.

Second, the heavy traditional tile roof was replaced with a lightweight metal alternative. This change reduced the roof’s total weight to approximately one-sixteenth of its original mass, significantly lowering the building’s centre of gravity and reducing the sway it would experience during an earthquake.

These measures successfully increased the building’s seismic performance rating from approximately 0.3 to over 1.0 on the Japan Building Disaster Prevention Association’s scale. A rating below 0.7 indicates a high probability of collapse in a major earthquake, while 1.0 is the recommended standard for safety. The developments are replicable, and serves as a reference for preserving other culturally significant buildings across Japan.